ADVERSE REACTIONS SECTION.

ADVERSE REACTIONS Because atovaquone and proguanil hydrochloride contains atovaquone and proguanil hydrochloride, the type and severity of adverse reactions associated with each of the compounds may be expected. The higher treatment doses of atovaquone and proguanil hydrochloride were less well tolerated than the lower prophylactic doses.Among adults who received atovaquone and proguanil hydrochloride for treatment of malaria, attributable adverse experiences that occurred in >=5% of patients were abdominal pain (17%), nausea (12%), vomiting (12%), headache (10%), diarrhea (8%), asthenia (8%), anorexia (5%), and dizziness (5%). Treatment was discontinued prematurely due to an adverse experience in of 436 adults treated with atovaquone and proguanil hydrochloride.Among pediatric patients (weighing 11 to 40 kg) who received atovaquone and proguanil hydrochloride for the treatment of malaria, attributable adverse experiences that occurred in >=5% of patients were vomiting (10%) and pruritus (6%). Vomiting occurred in 43 of 319 (13%) pediatric patients who did not have symptomatic malaria but were given treatment doses of atovaquone and proguanil hydrochloride for days in clinical trial. The design of this clinical trial required that any patient who vomited be withdrawn from the trial. Among pediatric patients with symptomatic malaria treated with atovaquone and proguanil hydrochloride, treatment was discontinued prematurely due to an adverse experience in of 116 (0.9%).In study of 100 pediatric patients (5 to <11 kg body weight) who received atovaquone and proguanil hydrochloride for the treatment of uncomplicated P. falciparum malaria, only diarrhea (6%) occurred in >=5% of patients as an adverse experience attributable to atovaquone and proguanil hydrochloride. In patients (3%), treatment was discontinued prematurely due to an adverse experience.Abnormalities in laboratory tests reported in clinical trials were limited to elevations of transaminases in malaria patients being treated with atovaquone and proguanil hydrochloride. The frequency of these abnormalities varied substantially across studies of treatment and were not observed in the randomized portions of the prophylaxis trials. In one phase III trial of malaria treatment in Thai adults, early elevations of ALT and AST were observed to occur more frequently in patients treated with atovaquone and proguanil hydrochloride compared to patients treated with an active control drug. Rates for patients who had normal baseline levels of these clinical laboratory parameters were: Day 7: ALT 26.7% vs. 15.6%; AST 16.9% vs. 8.6%. By day 14 of this 28-day study, the frequency of transaminase elevations equalized across the groups.In this and other studies in which transaminase elevations occurred, they were noted to persist for up to weeks following treatment with atovaquone and proguanil hydrochloride for malaria. None were associated with untoward clinical events.Among subjects who received atovaquone and proguanil hydrochloride for prophylaxis of malaria in placebo-controlled trials, adverse experiences occurred in similar proportions of subjects receiving atovaquone and proguanil hydrochloride or placebo (Table 3). The most commonly reported adverse experiences possibly attributable to atovaquone and proguanil hydrochloride or placebo were headache and abdominal pain. Prophylaxis with atovaquone and proguanil hydrochloride was discontinued prematurely due to treatment-related adverse experience in of 381 adults and of 125 pediatric patients.Table 3. Adverse Experiences in Placebo-Controlled Clinical Trials of Atovaquone and Proguanil hydrochloride for Prophylaxis of Malaria Percent of Subjects With Adverse Experiences (Percent of Subjects With Adverse Experiences Attributable to Therapy) Adverse ExperienceAdults Children and Adolescents Placebo n=206Atovaquone and Proguanil hydrochloride n=206Atovaquone and Proguanil hydrochloride n=381Placebo n=140Atovaquone and Proguanil hydrochloride n=125Headache27 (7)22 (3)17 (5)21 (14)19 (14)Fever13 (1)5 (0)3 (0)11 (<1)6 (0)Myalgia11 (0)12 (0)7 (0)0 (0)0 (0)Abdominal pain10 (5)9 (4)6 (3)29 (29)33 (31)Cough8 (<1)6 (<1)4 (1)9 (0)9 (0)Diarrhea8 (3)6 (2)4 (1)3 (1)2 (0)Upper respiratory infection7 (0)8 (0)5 (0)0 (0)<1 (0)Dyspepsia5 (4)3 (2)2 (1)0 (0)0 (0)Back pain4 (0)8 (0)4 (0)0 (0)0 (0)Gastritis3 (2)3 (3)2 (2)0 (0)0 (0)Vomiting2 (<1)1 (<1)<1 (<1)6 (6)7 (7)Flu syndrome1 (0)2 (0)4 (0)6 (0)9 (0)Any adverse experience65 (32)54 (17)49 (17)62 (41)60 (42)In an additional placebo-controlled study of malaria prophylaxis with atovaquone and proguanil hydrochloride involving 330 pediatric patients in malaria-endemic area (see CLINICAL STUDIES), the safety profile of atovaquone and proguanil hydrochloride was consistent with that described above. The most common treatment-emergent adverse events with atovaquone and proguanil hydrochloride were abdominal pain (13%), headache (13%), and cough (10%). Abdominal pain (13% vs. 8%) and vomiting (5% vs. 3%) were reported more often with atovaquone and proguanil hydrochloride than with placebo, while fever (5% vs. 12%) and diarrhea (1% vs. 5%) were more common with placebo. No patient withdrew from the study due to an adverse experience with atovaquone and proguanil hydrochloride. No routine laboratory data were obtained during this study.Among subjects who received atovaquone and proguanil hydrochloride for prophylaxis of malaria in clinical trials with an active comparator, adverse experiences occurred in similar or lower proportion of subjects receiving atovaquone and proguanil hydrochloride than an active comparator (Table 4). The mean durations of dosing and the periods for which the adverse experiences are summarized in Table 4, were 28 days (Study 1) and 26 days (Study 2) for atovaquone and proguanil hydrochloride, 53 days for mefloquine, and 49 days for chloroquine plus proguanil (reflecting the different recommended dosing regimens). Fewer neuropsychiatric adverse experiences occurred in subjects who received atovaquone and proguanil hydrochloride than mefloquine. Fewer gastrointestinal adverse experiences occurred in subjects receiving atovaquone and proguanil hydrochloride than chloroquine/proguanil. Compared with active comparator drugs, subjects receiving atovaquone and proguanil hydrochloride had fewer adverse experiences overall that were attributed to prophylactic therapy (Table 4). Prophylaxis with atovaquone and proguanil hydrochloride was discontinued prematurely due to treatment-related adverse experience in of 1,004 travelers.Table 4. Adverse Experiences in Active-Controlled Clinical Trials of Atovaquone and Proguanil hydrochloride for Prophylaxis of Malaria Adverse experiences that started while receiving active study drug. Percent of Subjects With Adverse Experiences (Percent of Subjects With Adverse Experiences Attributable to Therapy) Study Study Adverse ExperienceAtovaquone and Proguanil hydrochloride n=493Mefloquine n=483Atovaquone and Proguanil hydrochloride n=511Chloroquine Plus Proguanil n=511Diarrhea38 (8)36 (7)34 (5)39 (7)Nausea14 (3)20 (8)11 (2)18 (7)Abdominal pain17 (5)16 (5)14 (3)22 (6)Headache12 (4)17 (7)12 (4)14 (4)Dreams7 (7)16 (14)6 (4)7 (3)Insomnia5 (3)16 (13)4 (2)5 (2)Fever9 (<1)11 (1)8 (<1)8 (<1)Dizziness5 (2)14 (9)7 (3)8 (4)Vomiting8 (1)10 (2)8 (0)14 (2)Oral ulcers9 (6)6 (4)5 (4)7 (5)Pruritus4 (2)5 (2)3 (1)2 (<1)Visual difficulties2 (2)5 (3)3 (2)3 (2)Depression<1 (<1)5 (4)<1 (<1)1 (<1)Anxiety1 (<1)5 (4)<1 (<1)1 (<1)Any adverse experience64 (30)69 (42)58 (22)66 (28)Any neuropsychiatric event20 (14)37 (29)16 (10)20 (10)Any GI event49 (16)50 (19)43 (12)54 (20)In third active-controlled study, atovaquone and proguanil hydrochloride (n 110) was compared with chloroquine/proguanil (n 111) for the prophylaxis of malaria in 221 non-immune pediatric patients (see CLINICAL STUDIES). The mean duration of exposure was 23 days for atovaquone and proguanil hydrochloride, 46 days for chloroquine, and 43 days for proguanil, reflecting the different recommended dosage regimens for these products. Fewer patients treated with atovaquone and proguanil hydrochloride reported abdominal pain (2% vs. 7%) or nausea (<1% vs. 7%) than children who received chloroquine/proguanil. Oral ulceration (2% vs. 2%), vivid dreams (2% vs. <1%), and blurred vision (0% vs. 2%) occurred in similar proportions of patients receiving either atovaquone and proguanil hydrochloride or chloroquine/proguanil, respectively. Two patients discontinued prophylaxis with chloroquine/proguanil due to adverse events, while none of those receiving atovaquone and proguanil hydrochloride discontinued due to adverse events. Post-Marketing Adverse Reactions:. In addition to adverse events reported from clinical trials, the following events have been identified during world-wide post-approval use of atovaquone and proguanil hydrochloride. Because they are reported voluntarily from population of unknown size, estimates of frequency cannot be made. These events have been chosen for inclusion due to combination of their seriousness, frequency of reporting, or potential causal connection to atovaquone and proguanil hydrochloride. Blood and Lymphatic System Disorders: Neutropenia and rarely anemia. Pancytopenia in patients with severe renal impairment treated with proguanil.Immune System Disorders:Allergic reactions including angioedema, urticaria, and rare cases of anaphylaxis and vasculitis. Nervous System Disorders: Rare cases of seizures and psychotic events (such as hallucinations); however, causal relationship has not been established. Gastrointestinal Disorders: Stomatitis.Hepatobiliary Disorders: Elevated liver function tests and rare cases of hepatitis; single case of hepatitis, cholestatis; failure requiring transplant has been reported.Skin and Subcutaneous Tissue Disorders: Photosensitivity, rash, and rare cases of erythema multiforme and Stevens-Johnson syndrome.

CLINICAL PHARMACOLOGY SECTION.

CLINICAL PHARMACOLOGY Microbiology:. Mechanism of Action:. The constituents of atovaquone and proguanil hydrochloride interfere with different pathways involved in the biosynthesis of pyrimidines required for nucleic acid replication. Atovaquone is selective inhibitor of parasite mitochondrial electron transport. Proguanil hydrochloride primarily exerts its effect by means of the metabolite cycloguanil, dihydrofolate reductase inhibitor. Inhibition of dihydrofolate reductase in the malaria parasite disrupts deoxythymidylate synthesis. Activity In Vitro and In Vivo: Atovaquone and cycloguanil (an active metabolite of proguanil) are active against the erythrocytic and exoerythrocytic stages of Plasmodium spp. Enhanced efficacy of the combination compared to either atovaquone or proguanil hydrochloride alone was demonstrated in clinical studies in both immune and non-immune patients (see CLINICAL STUDIES). Drug Resistance: Strains of P. falciparum with decreased susceptibility to atovaquone or proguanil/cycloguanil alone can be selected in vitro or in vivo. The combination of atovaquone and proguanil hydrochloride may not be effective for treatment of recrudescent malaria that develops after prior therapy with the combination. Pharmacokinetics:. Absorption: Atovaquone is highly lipophilic compound with low aqueous solubility. The bioavailability of atovaquone shows considerable inter-individual variability. Dietary fat taken with atovaquone increases the rate and extent of absorption, increasing AUC to times and Cmax times over fasting. The absolute bioavailability of the tablet formulation of atovaquone when taken with food is 23%. Atovaquone and proguanil hydrochloride tablets should be taken with food or milky drink. Proguanil hydrochloride is extensively absorbed regardless of food intake. Distribution: Atovaquone is highly protein bound (>99%) over the concentration range of to 90 mcg/mL. population pharmacokinetic analysis demonstrated that the apparent volume of distribution of atovaquone (V/F) in adult and pediatric patients after oral administration is approximately 8.8 L/kg.Proguanil is 75% protein bound. population pharmacokinetic analysis demonstrated that the apparent V/F of proguanil in adult and pediatric patients >15 years of age with body weights from 31 to 110 kg ranged from 1,617 to 2,502 L. In pediatric patients <=15 years of age with body weights from 11 to 56 kg, the V/F of proguanil ranged from 462 to 966 L. In human plasma, the binding of atovaquone and proguanil was unaffected by the presence of the other. Metabolism: In study where 14C-labeled atovaquone was administered to healthy volunteers, greater than 94% of the dose was recovered as unchanged atovaquone in the feces over 21 days. There was little or no excretion of atovaquone in the urine (less than 0.6%). There is indirect evidence that atovaquone may undergo limited metabolism; however, specific metabolite has not been identified. Between 40% to 60% of proguanil is excreted by the kidneys. Proguanil is metabolized to cycloguanil (primarily via CYP2C19) and 4-chlorophenylbiguanide. The main routes of elimination are hepatic biotransformation and renal excretion. Elimination: The elimination half-life of atovaquone is about to days in adult patients.The elimination half-life of proguanil is 12 to 21 hours in both adult patients and pediatric patients, but may be longer in individuals who are slow metabolizers.A population pharmacokinetic analysis in adult and pediatric patients showed that the apparent clearance (CL/F) of both atovaquone and proguanil are related to the body weight. The values CL/F for both atovaquone and proguanil in subjects with body weight >=11 kg are shown in Table 1. Table 1. Apparent Clearance for Atovaquone and Proguanil in Patients as Function of Body Weight Body WeightAtovaquoneProguanilNCL/F (L/hr) Mean +- SD (range)NCL/F (L/hr) Mean +- SD (range)11-20 Kg1591.34 +- 0.63 (0.52-4.26)14629.5 +- 6.5 (10.3-48.3)21-30 Kg1171.87 +- 0.81 (0.52-5.38)11340.0 +- 7.5 (15.9-62.7)31-40 Kg952.76 +- 2.07 (0.97-12.5)9149.5 +- 8.30 (25.8-71.5)> 40 Kg3686.61 +- 3.92 (1.32-20.3)28267.9 +- 19.9 (14.0 145)The pharmacokinetics of atovaquone and proguanil in patients with body weight below 11 kg have not been adequately characterized.. Special Populations:. Pediatrics: The pharmacokinetics of proguanil and cycloguanil are similar in adult patients and pediatric patients. However, the elimination half-life of atovaquone is shorter in pediatric patients (1 to days) than in adult patients (2 to days). In clinical trials, plasma trough levels of atovaquone and proguanil in pediatric patients weighing to 40 kg were within the range observed in adults after dosing by body weight. Geriatrics: In single-dose study, the pharmacokinetics of atovaquone, proguanil, and cycloguanil were compared in 13 elderly subjects (age 65 to 79 years) to 13 younger subjects (age 30 to 45 years). In the elderly subjects, the extent of systemic exposure (AUC) of cycloguanil was increased (point estimate 2.36, CI 1.70, 3.28). Tmax was longer in elderly subjects (median hours) compared with younger subjects (median hours) and average elimination half-life was longer in elderly subjects (mean 14.9 hours) compared with younger subjects (mean 8.3 hours). Hepatic Impairment: In single-dose study, the pharmacokinetics of atovaquone, proguanil, and cycloguanil were compared in 13 subjects with hepatic impairment (9 mild, moderate, as indicated by the Child-Pugh method) to 13 subjects with normal hepatic function. In subjects with mild or moderate hepatic impairment as compared to healthy subjects, there were no marked differences (<50%) in the rate or extent of systemic exposure of atovaquone. However, in subjects with moderate hepatic impairment, the elimination half-life of atovaquone was increased (point estimate 1.28, 90% CI 1.00 to 1.63). Proguanil AUC, Cmax, and its t1/2 increased in subjects with mild hepatic impairment when compared to healthy subjects (Table 2). Also, the proguanil AUC and its t1/2 increased in subjects with moderate hepatic impairment when compared to healthy subjects. Consistent with the increase in proguanil AUC, there were marked decreases in the systemic exposure of cycloguanil (Cmax and AUC) and an increase in its elimination half-life in subjects with mild hepatic impairment when compared to healthy volunteers (Table 2). There were few measurable cycloguanil concentrations in subjects with moderate hepatic impairment (see DOSAGE AND ADMINISTRATION). The pharmacokinetics of atovaquone, proguanil, and cycloguanil after administration of tovaquone and proguanil hydrochloride have not been studied in patients with severe hepatic impairment. Table 2. Point Estimates (90% CI) for Proguanil and Cycloguanil Parameters in Subjects With Mild and Moderate Hepatic Impairment Compared to Healthy Volunteers ND not determined due to lack of quantifiable data.ParameterComparisonProguanilCycloguanilAUC (0-inf) mild healthy1.96 (1.51, 2.54)0.32 (0.22, 0.45)Cmax Ratio of geometric means. mild healthy1.41 (1.16, 1.71)0.35 (0.24, 0.50)T 1/2Mean difference. mild healthy1.21 (0.92, 1.60)0.86 (0.49, 1.48)AUC (0-inf) moderate healthy1.64 (1.14, 2.34)NDCmax moderate healthy0.97 (0.69, 1.36)NDT 1/2 moderate healthy1.46 (1.05, 2.05)ND. Renal Impairment: In patients with mild renal impairment (creatinine clearance 50 to 80 mL/min), oral clearance and/or AUC data for atovaquone, proguanil, and cycloguanil are within the range of values observed in patients with normal renal function (creatinine clearance >80 mL/min). In patients with moderate renal impairment (creatinine clearance 30 to 50 mL/min), mean oral clearance for proguanil was reduced by approximately 35% compared with patients with normal renal function (creatinine clearance >80 mL/min) and the oral clearance of atovaquone was comparable between patients with normal renal function and mild renal impairment. No data exist on the use of atovaquone and proguanil hydrochloride for long-term prophylaxis (over months) in individuals with moderate renal failure. In patients with severe renal impairment (creatinine clearance <30 mL/min), atovaquone Cmax and AUC are reduced but the elimination half-lives for proguanil and cycloguanil are prolonged, with corresponding increases in AUC, resulting in the potential of drug accumulation and toxicity with repeated dosing (see CONTRAINDICATIONS). Drug Interactions:. There are no pharmacokinetic interactions between atovaquone and proguanil at the recommended dose. Concomitant treatment with tetracycline has been associated with approximately 40% reduction in plasma concentrations of atovaquone. Concomitant treatment with metoclopramide has also been associated with decreased bioavailability of atovaquone. Concomitant administration of rifampin or rifabutin is known to reduce atovaquone levels by approximately 50% and 34%, respectively (see PRECAUTIONS: Drug Interactions). The mechanisms of these interactions are unknown. Concomitant administration of atovaquone (750 mg BID with food for 14 days) and indinavir (800 mg TID without food for 14 days) did not result in any change in the steady-state AUC and Cmax of indinavir but resulted in decrease in the Ctrough of indinavir (23% decrease [90% CI 8%, 35%]). Caution should be exercised when prescribing atovaquone with indinavir due to the decrease in trough levels of indinavir.Atovaquone is highly protein bound (>99%) but does not displace other highly protein-bound drugs in vitro, indicating significant drug interactions arising from displacement are unlikely (see PRECAUTIONS: Drug Interactions). Proguanil is metabolized primarily by CYP2C19. Potential pharmacokinetic interactions with other substrates or inhibitors of this pathway are unknown.

CLINICAL STUDIES SECTION.

CLINICAL STUDIES Treatment of Acute Malarial Infections:. In phase II clinical trials, atovaquone alone, proguanil hydrochloride alone, and the combination of atovaquone and proguanil hydrochloride were evaluated for the treatment of acute, uncomplicated malaria caused by P. falciparum. Among 156 evaluable patients, the parasitological cure rate was 59/89 (66%) with atovaquone alone, 1/17 (6%) with proguanil hydrochloride alone, and 50/50 (100%) with the combination of atovaquone and proguanil hydrochloride. Atovaquone and proguanil hydrochloride was evaluated for treatment of acute, uncomplicated malaria caused by P. falciparum in phase III controlled clinical trials. Among 471 evaluable patients treated with the equivalent of atovaquone and proguanil hydrochloride tablets once daily for days, 464 had sensitive response (elimination of parastextia with no recurrent parastextia during follow-up for 28 days) (see Table 5). Seven patients had response of RI resistance (elimination of parastextia but with recurrent parastextia between and 28 days after starting treatment). In these trials, the response to treatment with atovaquone and proguanil hydrochloride was similar to treatment with the comparator drug in trials, and better than the response to treatment with the comparator drug in the other trials. The overall efficacy in 521 evaluable patients was 98.7% (Table 5).Table 5. Parasitological Response in Clinical Trials of Atovaquone and Proguanil hydrochloride for Treatment of P. falciparum Malaria Atovaquone and proguanil hydrochloride Comparator Study SiteEvaluable Patients (n)% Sensitive ResponseElimination of parastextia with no recurrent parastextia during follow-up for 28 days. Drug (s)Evaluable Patients (n)% Sensitive Response Brazil7498.6%Quinine and tetracycline76100.0%Thailand79100.0%Mefloquine7986.1%FrancePatients hospitalized only for acute care. Follow-up conducted in outpatients. 21100.0%Halofantrine18100.0%Kenya, 8193.8%Halofantrine8390.4%Zambia80100.0%Pyrimethamine/sulfadoxine (P/S)8098.8%Gabon 6398.4%Amodiaquine6381.0%Phillipines54100.0%Chloroquine (C/q) Cq and P/S23 3230.4% 87.5%Peru19100.0%Chloroquine P/S13 77.7% 100.0%Eighteen of 521 (3.5%) evaluable patients with acute falciparum malaria presented with pretreatment serum creatinine greater than 2.0 mg/dL (range 2.1 to 4.3 mg/dL). All were successfully treated with atovaquone and proguanil hydrochloride and 17 of 18 (94.4%) had normal serum creatinine levels by day 7. Data from phase II trial of atovaquone conducted in Zambia suggested that approximately 40% of the study population in this country were HIV-infected patients. The enrollment criteria were similar for the phase III trial of atovaquone and proguanil hydrochloride conducted in Zambia and the results are presented in Table 5. Efficacy rates for atovaquone and proguanil hydrochloride in this study population were high and comparable to other populations studied.The efficacy of atovaquone and proguanil hydrochloride in the treatment of the erythrocytic phase of nonfalciparum malaria was assessed in small number of patients. Of the 23 patients in Thailand infected with P. vivax and treated with atovaquone/proguanil hydrochloride 1,000 mg/400 mg daily for days, parastextia cleared in 21 (91.3%) at days. Parasite relapse occurred commonly when P. vivax malaria was treated with atovaquone and proguanil hydrochloride alone. Seven patients in Gabon with malaria due to P. ovale or P. malariae were treated with atovaquone/proguanil hydrochloride 1,000 mg/400 mg daily for days. All evaluable patients (3 with P. malariae, with P. ovale, and with mixed P. falciparum and P. ovale) were cured at 28 days. Relapsing malarias including P. vivax and P. ovale require additional treatment to prevent relapse.. Prevention of Malaria:. Atovaquone and proguanil hydrochloride was evaluated for prophylaxis of malaria in clinical trials in malaria-endemic areas and in active-controlled trials in non-immune travelers to malaria-endemic areas.Three placebo-controlled studies of 10 to 12 weeks duration were conducted among residents of malaria-endemic areas in Kenya, Zambia, and Gabon. Of total of 669 randomized patients (including 264 pediatric patients to 16 years of age), 103 were withdrawn for reasons other than falciparum malaria or drug-related adverse events. (Fifty-five percent of these were lost to follow-up and 45% were withdrawal for protocol violations). The results are listed in Table 6.Table 6. Prevention of Parastextia in Placebo-Controlled Clinical Trials of Atovaquone and Proguanil hydrochloride for Prophylaxis of P. falciparum Malaria in Residents of Malaria-Endemic Areas Atovaquone and proguanil hydrochloridePlaceboTotal number of patients randomized326341Failed to complete study5744Developed parastextia (P. falciparum)292In another study, 330 Gabonese pediatric patients (weighing 13 to 40 kg, and aged to 14 years) who had received successful open-label radical cure treatment with artesunate, were randomized to receive either atovaquone and proguanil hydrochloride (dosage based on body weight) or placebo in double-blind fashion for 12 weeks. Blood smears were obtained weekly and any time malaria was suspected. Nineteen of the 165 children given atovaquone and proguanil hydrochloride and 18 of 165 patients given placebo withdrew from the study for reasons other than parastextia (primary reason was lost to follow-up). In the per-protocol population, out of 150 patients (<1%) who received atovaquone and proguanil hydrochloride developed P. falciparum parastextia while receiving prophylaxis with atovaquone and proguanil hydrochloride compared with 31 (22%) of the 144 placebo recipients.In 10-week study in 175 South African subjects who moved into malaria-endemic areas and were given prophylaxis with atovaquone and proguanil hydrochloride daily, parastextia developed in subject who missed several doses of medication. Since no placebo control was included, the incidence of malaria in this study was not known. Two active-controlled studies were conducted in non-immune travelers who visited malaria-endemic area. The mean duration of travel was 18 days (range to 38 days). Of total of 1,998 randomized patients who received atovaquone and proguanil hydrochloride or controlled drug, 24 discontinued from the study before follow-up evaluation 60 days after leaving the endemic area. Nine of these were lost to follow-up, withdrew because of an adverse experience, and 13 were discontinued for other reasons. These studies were not large enough to allow for statements of comparative efficacy. In addition, the true exposure rate to P. falciparum malaria in both studies is unknown. The results are listed in Table 7. Table 7. Prevention of Parastextia in Active-Controlled Clinical Trials of Atovaquone and Proguanil hydrochloride for Prophylaxis of P. falciparum Malaria in Non-Immune Travelers Atovaquone and Proguanil hydrochlorideMefloquineChloroquine Plus ProguanilTotal number of randomized patients who received study drug1,004483511Failed to complete study1464Developed parastextia (P. falciparum)003A third randomized, open-label study was conducted which included 221 otherwise healthy pediatric patients (weighing >=11 kg and to 17 years of age) who were at risk of contracting malaria by traveling to an endemic area. The mean duration of travel was 15 days (range to 30 days). Prophylaxis with atovaquone and proguanil hydrochloride (n 110, dosage based on body weight) began or days before entering the endemic area and lasted until days after leaving the area. control group (n 111) received prophylaxis with chloroquine/proguanil dosed according to WHO guidelines. No cases of malaria occurred in either group of children. However, the study was not large enough to allow for statements of comparative efficacy. In addition, the true exposure rate to P. falciparum malaria in this study is unknown.In malaria challenge study conducted in healthy US volunteers, atovaquone alone prevented malaria in of individuals, whereas of placebo-treated volunteers developed malaria.. Causal Prophylaxis: In separate studies with small numbers of volunteers, atovaquone and proguanil hydrochloride were independently shown to have causal prophylactic activity directed against liver-stage parasites of P. falciparum. Six patients given single dose of atovaquone 250 mg 24 hours prior to malaria challenge were protected from developing malaria, whereas all placebo-treated patients developed malaria. During the weeks following cessation of prophylaxis in clinical trial participants who remained in malaria-endemic areas and were available for evaluation, malaria developed in 24 of 211 (11.4%) subjects who took placebo and of 328 (2.7%) who took atovaquone and proguanil hydrochloride While new infections could not be distinguished from recrudescent infections, all but of the infections in patients treated with atovaquone and proguanil hydrochloride occurred more than 15 days after stopping therapy, probably representing new infections. The single case occurring on day following cessation of therapy with atovaquone and proguanil hydrochloride probably represents failure of prophylaxis with atovaquone and proguanil hydrochloride. The possibility that delayed cases of P. falciparum malaria may occur some time after stopping prophylaxis with atovaquone and proguanil hydrochloride cannot be ruled out. Hence, returning travelers developing febrile illnesses should be investigated for malaria.

INFORMATION FOR PATIENTS SECTION.

Information for Patients: Patients should be instructed:oto take atovaquone and proguanil hydrochloride tablets at the same time each day with food or milky drink.oto take repeat dose of atovaquone and proguanil hydrochloride if vomiting occurs within hour after dosing.oto take dose as soon as possible if dose is missed, then return to their normal dosing schedule. However, if dose is skipped, the patient should not double the next dose.othat rare serious adverse events such as hepatitis, severe skin reactions, neurological, and hematological events have been reported when atovaquone and proguanil hydrochloride was used for the prophylaxis or treatment of malaria.oto consult healthcare professional regarding alternative forms of prophylaxis if prophylaxis with atovaquone and proguanil hydrochloride is prematurely discontinued for any reason.othat protective clothing, insect repellants, and bednets are important components of malaria prophylaxis.othat no chemoprophylactic regimen is 100% effective; therefore, patients should seek medical attention for any febrile illness that occurs during or after return from malaria-endemic area and inform their healthcare professional that they may have been exposed to malaria. othat falciparum malaria carries higher risk of death and serious complications in pregnant women than in the general population. Pregnant women anticipating travel to malarious areas should discuss the risks and benefits of such travel with their physicians (see Pregnancy section).. oto take atovaquone and proguanil hydrochloride tablets at the same time each day with food or milky drink.. oto take repeat dose of atovaquone and proguanil hydrochloride if vomiting occurs within hour after dosing.. oto take dose as soon as possible if dose is missed, then return to their normal dosing schedule. However, if dose is skipped, the patient should not double the next dose.. othat rare serious adverse events such as hepatitis, severe skin reactions, neurological, and hematological events have been reported when atovaquone and proguanil hydrochloride was used for the prophylaxis or treatment of malaria.. oto consult healthcare professional regarding alternative forms of prophylaxis if prophylaxis with atovaquone and proguanil hydrochloride is prematurely discontinued for any reason.. othat protective clothing, insect repellants, and bednets are important components of malaria prophylaxis.. othat no chemoprophylactic regimen is 100% effective; therefore, patients should seek medical attention for any febrile illness that occurs during or after return from malaria-endemic area and inform their healthcare professional that they may have been exposed to malaria. othat falciparum malaria carries higher risk of death and serious complications in pregnant women than in the general population. Pregnant women anticipating travel to malarious areas should discuss the risks and benefits of such travel with their physicians (see Pregnancy section).

PHARMACOKINETICS SECTION.

Pharmacokinetics:. Absorption: Atovaquone is highly lipophilic compound with low aqueous solubility. The bioavailability of atovaquone shows considerable inter-individual variability. Dietary fat taken with atovaquone increases the rate and extent of absorption, increasing AUC to times and Cmax times over fasting. The absolute bioavailability of the tablet formulation of atovaquone when taken with food is 23%. Atovaquone and proguanil hydrochloride tablets should be taken with food or milky drink. Proguanil hydrochloride is extensively absorbed regardless of food intake. Distribution: Atovaquone is highly protein bound (>99%) over the concentration range of to 90 mcg/mL. population pharmacokinetic analysis demonstrated that the apparent volume of distribution of atovaquone (V/F) in adult and pediatric patients after oral administration is approximately 8.8 L/kg.Proguanil is 75% protein bound. population pharmacokinetic analysis demonstrated that the apparent V/F of proguanil in adult and pediatric patients >15 years of age with body weights from 31 to 110 kg ranged from 1,617 to 2,502 L. In pediatric patients <=15 years of age with body weights from 11 to 56 kg, the V/F of proguanil ranged from 462 to 966 L. In human plasma, the binding of atovaquone and proguanil was unaffected by the presence of the other. Metabolism: In study where 14C-labeled atovaquone was administered to healthy volunteers, greater than 94% of the dose was recovered as unchanged atovaquone in the feces over 21 days. There was little or no excretion of atovaquone in the urine (less than 0.6%). There is indirect evidence that atovaquone may undergo limited metabolism; however, specific metabolite has not been identified. Between 40% to 60% of proguanil is excreted by the kidneys. Proguanil is metabolized to cycloguanil (primarily via CYP2C19) and 4-chlorophenylbiguanide. The main routes of elimination are hepatic biotransformation and renal excretion. Elimination: The elimination half-life of atovaquone is about to days in adult patients.The elimination half-life of proguanil is 12 to 21 hours in both adult patients and pediatric patients, but may be longer in individuals who are slow metabolizers.A population pharmacokinetic analysis in adult and pediatric patients showed that the apparent clearance (CL/F) of both atovaquone and proguanil are related to the body weight. The values CL/F for both atovaquone and proguanil in subjects with body weight >=11 kg are shown in Table 1. Table 1. Apparent Clearance for Atovaquone and Proguanil in Patients as Function of Body Weight Body WeightAtovaquoneProguanilNCL/F (L/hr) Mean +- SD (range)NCL/F (L/hr) Mean +- SD (range)11-20 Kg1591.34 +- 0.63 (0.52-4.26)14629.5 +- 6.5 (10.3-48.3)21-30 Kg1171.87 +- 0.81 (0.52-5.38)11340.0 +- 7.5 (15.9-62.7)31-40 Kg952.76 +- 2.07 (0.97-12.5)9149.5 +- 8.30 (25.8-71.5)> 40 Kg3686.61 +- 3.92 (1.32-20.3)28267.9 +- 19.9 (14.0 145)The pharmacokinetics of atovaquone and proguanil in patients with body weight below 11 kg have not been adequately characterized.. Special Populations:. Pediatrics: The pharmacokinetics of proguanil and cycloguanil are similar in adult patients and pediatric patients. However, the elimination half-life of atovaquone is shorter in pediatric patients (1 to days) than in adult patients (2 to days). In clinical trials, plasma trough levels of atovaquone and proguanil in pediatric patients weighing to 40 kg were within the range observed in adults after dosing by body weight. Geriatrics: In single-dose study, the pharmacokinetics of atovaquone, proguanil, and cycloguanil were compared in 13 elderly subjects (age 65 to 79 years) to 13 younger subjects (age 30 to 45 years). In the elderly subjects, the extent of systemic exposure (AUC) of cycloguanil was increased (point estimate 2.36, CI 1.70, 3.28). Tmax was longer in elderly subjects (median hours) compared with younger subjects (median hours) and average elimination half-life was longer in elderly subjects (mean 14.9 hours) compared with younger subjects (mean 8.3 hours). Hepatic Impairment: In single-dose study, the pharmacokinetics of atovaquone, proguanil, and cycloguanil were compared in 13 subjects with hepatic impairment (9 mild, moderate, as indicated by the Child-Pugh method) to 13 subjects with normal hepatic function. In subjects with mild or moderate hepatic impairment as compared to healthy subjects, there were no marked differences (<50%) in the rate or extent of systemic exposure of atovaquone. However, in subjects with moderate hepatic impairment, the elimination half-life of atovaquone was increased (point estimate 1.28, 90% CI 1.00 to 1.63). Proguanil AUC, Cmax, and its t1/2 increased in subjects with mild hepatic impairment when compared to healthy subjects (Table 2). Also, the proguanil AUC and its t1/2 increased in subjects with moderate hepatic impairment when compared to healthy subjects. Consistent with the increase in proguanil AUC, there were marked decreases in the systemic exposure of cycloguanil (Cmax and AUC) and an increase in its elimination half-life in subjects with mild hepatic impairment when compared to healthy volunteers (Table 2). There were few measurable cycloguanil concentrations in subjects with moderate hepatic impairment (see DOSAGE AND ADMINISTRATION). The pharmacokinetics of atovaquone, proguanil, and cycloguanil after administration of tovaquone and proguanil hydrochloride have not been studied in patients with severe hepatic impairment. Table 2. Point Estimates (90% CI) for Proguanil and Cycloguanil Parameters in Subjects With Mild and Moderate Hepatic Impairment Compared to Healthy Volunteers ND not determined due to lack of quantifiable data.ParameterComparisonProguanilCycloguanilAUC (0-inf) mild healthy1.96 (1.51, 2.54)0.32 (0.22, 0.45)Cmax Ratio of geometric means. mild healthy1.41 (1.16, 1.71)0.35 (0.24, 0.50)T 1/2Mean difference. mild healthy1.21 (0.92, 1.60)0.86 (0.49, 1.48)AUC (0-inf) moderate healthy1.64 (1.14, 2.34)NDCmax moderate healthy0.97 (0.69, 1.36)NDT 1/2 moderate healthy1.46 (1.05, 2.05)ND. Renal Impairment: In patients with mild renal impairment (creatinine clearance 50 to 80 mL/min), oral clearance and/or AUC data for atovaquone, proguanil, and cycloguanil are within the range of values observed in patients with normal renal function (creatinine clearance >80 mL/min). In patients with moderate renal impairment (creatinine clearance 30 to 50 mL/min), mean oral clearance for proguanil was reduced by approximately 35% compared with patients with normal renal function (creatinine clearance >80 mL/min) and the oral clearance of atovaquone was comparable between patients with normal renal function and mild renal impairment. No data exist on the use of atovaquone and proguanil hydrochloride for long-term prophylaxis (over months) in individuals with moderate renal failure. In patients with severe renal impairment (creatinine clearance <30 mL/min), atovaquone Cmax and AUC are reduced but the elimination half-lives for proguanil and cycloguanil are prolonged, with corresponding increases in AUC, resulting in the potential of drug accumulation and toxicity with repeated dosing (see CONTRAINDICATIONS). Drug Interactions:. There are no pharmacokinetic interactions between atovaquone and proguanil at the recommended dose. Concomitant treatment with tetracycline has been associated with approximately 40% reduction in plasma concentrations of atovaquone. Concomitant treatment with metoclopramide has also been associated with decreased bioavailability of atovaquone. Concomitant administration of rifampin or rifabutin is known to reduce atovaquone levels by approximately 50% and 34%, respectively (see PRECAUTIONS: Drug Interactions). The mechanisms of these interactions are unknown. Concomitant administration of atovaquone (750 mg BID with food for 14 days) and indinavir (800 mg TID without food for 14 days) did not result in any change in the steady-state AUC and Cmax of indinavir but resulted in decrease in the Ctrough of indinavir (23% decrease [90% CI 8%, 35%]). Caution should be exercised when prescribing atovaquone with indinavir due to the decrease in trough levels of indinavir.Atovaquone is highly protein bound (>99%) but does not displace other highly protein-bound drugs in vitro, indicating significant drug interactions arising from displacement are unlikely (see PRECAUTIONS: Drug Interactions). Proguanil is metabolized primarily by CYP2C19. Potential pharmacokinetic interactions with other substrates or inhibitors of this pathway are unknown.

PRECAUTIONS SECTION.

PRECAUTIONS General: Atovaquone and proguanil hydrochloride has not been evaluated for the treatment of cerebral malaria or other severe manifestations of complicated malaria, including hyperparastextia, pulmonary edema, or renal failure. Patients with severe malaria are not candidates for oral therapy. Elevated liver function tests and rare cases of hepatitis have been reported with prophylactic use of atovaquone and proguanil hydrochloride. single case of hepatic failure requiring liver transplantation has also been reported with prophylactic use. Absorption of atovaquone may be reduced in patients with diarrhea or vomiting. If atovaquone and proguanil hydrochloride is used in patients who are vomiting (see DOSAGE AND ADMINISTRATION), parastextia should be closely monitored and the use of an antiemetic considered. Vomiting occurred in up to 19% of pediatric patients given treatment doses of atovaquone and proguanil hydrochloride. In the controlled clinical trials of atovaquone and proguanil hydrochloride, 15.3% of adults who were treated with atovaquone/proguanil received an antiemetic drug during that part of the trial when they received atovaquone/proguanil. Of these patients, 98.3% were successfully treated. In patients with severe or persistent diarrhea or vomiting, alternative antimalarial therapy may be required. Parasite relapse occurred commonly when P. vivax malaria was treated with atovaquone and proguanil hydrochloride alone. In the event of recrudescent P. falciparum infections after treatment with atovaquone and proguanil hydrochloride or failure of chemoprophylaxis with atovaquone and proguanil hydrochloride, patients should be treated with different blood schizonticide.. Information for Patients: Patients should be instructed:oto take atovaquone and proguanil hydrochloride tablets at the same time each day with food or milky drink.oto take repeat dose of atovaquone and proguanil hydrochloride if vomiting occurs within hour after dosing.oto take dose as soon as possible if dose is missed, then return to their normal dosing schedule. However, if dose is skipped, the patient should not double the next dose.othat rare serious adverse events such as hepatitis, severe skin reactions, neurological, and hematological events have been reported when atovaquone and proguanil hydrochloride was used for the prophylaxis or treatment of malaria.oto consult healthcare professional regarding alternative forms of prophylaxis if prophylaxis with atovaquone and proguanil hydrochloride is prematurely discontinued for any reason.othat protective clothing, insect repellants, and bednets are important components of malaria prophylaxis.othat no chemoprophylactic regimen is 100% effective; therefore, patients should seek medical attention for any febrile illness that occurs during or after return from malaria-endemic area and inform their healthcare professional that they may have been exposed to malaria. othat falciparum malaria carries higher risk of death and serious complications in pregnant women than in the general population. Pregnant women anticipating travel to malarious areas should discuss the risks and benefits of such travel with their physicians (see Pregnancy section).. oto take atovaquone and proguanil hydrochloride tablets at the same time each day with food or milky drink.. oto take repeat dose of atovaquone and proguanil hydrochloride if vomiting occurs within hour after dosing.. oto take dose as soon as possible if dose is missed, then return to their normal dosing schedule. However, if dose is skipped, the patient should not double the next dose.. othat rare serious adverse events such as hepatitis, severe skin reactions, neurological, and hematological events have been reported when atovaquone and proguanil hydrochloride was used for the prophylaxis or treatment of malaria.. oto consult healthcare professional regarding alternative forms of prophylaxis if prophylaxis with atovaquone and proguanil hydrochloride is prematurely discontinued for any reason.. othat protective clothing, insect repellants, and bednets are important components of malaria prophylaxis.. othat no chemoprophylactic regimen is 100% effective; therefore, patients should seek medical attention for any febrile illness that occurs during or after return from malaria-endemic area and inform their healthcare professional that they may have been exposed to malaria. othat falciparum malaria carries higher risk of death and serious complications in pregnant women than in the general population. Pregnant women anticipating travel to malarious areas should discuss the risks and benefits of such travel with their physicians (see Pregnancy section).. Drug Interactions: Concomitant treatment with tetracycline has been associated with approximately 40% reduction in plasma concentrations of atovaquone. Parastextia should be closely monitored in patients receiving tetracycline. While antiemetics may be indicated for patients receiving atovaquone and proguanil hydrochloride, metoclopramide may reduce the bioavailability of atovaquone and should be used only if other antiemetics are not available.Concomitant administration of rifampin or rifabutin is known to reduce atovaquone levels by approximately 50% and 34%, respectively. The concomitant administration of atovaquone and proguanil hydrochloride and rifampin or rifabutin is not recommended.Proguanil may potentiate the anticoagulant effect of warfarin and other coumarin-based anticoagulants. The mechanism of this potential drug interaction has not been established. Caution is advised when initiating or withdrawing malaria prophylaxis or treatment with atovaquone and proguanil hydrochloride in patients on continuous treatment with coumarin-based anticoagulants. When these products are administered concomitantly, suitable coagulation tests should be closely monitored. Atovaquone is highly protein bound (>99%) but does not displace other highly protein-bound drugs in vitro, indicating significant drug interactions arising from displacement are unlikely. Potential interactions between proguanil or cycloguanil and other drugs that are CYP2C19 substrates or inhibitors are unknown. Carcinogenesis, Mutagenesis, Impairment of Fertility: Atovaquone: Carcinogenicity studies in rats were negative; 24-month studies in mice showed treatment-related increases in incidence of hepatocellular adenoma and hepatocellular carcinoma at all doses tested which ranged from approximately to times the average steady-state plasma concentrations in humans during prophylaxis of malaria. Atovaquone was negative with or without metabolic activation in the Ames Salmonella mutagenicity assay, the Mouse Lymphoma mutagenesis assay, and the Cultured Human Lymphocyte cytogenetic assay. No evidence of genotoxicity was observed in the in vivo Mouse Micronucleus assay.. Proguanil: No evidence of carcinogenic effect was observed in 24-month studies conducted in CD-1 mice (doses up to 1.5 times the average systemic human exposure based on AUC) and in Wistar Hannover rats (doses up to 1.1 times the average systemic human exposure). Proguanil was negative with or without metabolic activation in the Ames Salmonella mutagenicity assay and the Mouse Lymphoma mutagenesis assay. No evidence of genotoxicity was observed in the in vivo Mouse Micronucleus assay.Cycloguanil, the active metabolite of proguanil, was also negative in the Ames test, but was positive in the Mouse Lymphoma assay and the Mouse Micronucleus assay. These positive effects with cycloguanil, dihydrofolate reductase inhibitor, were significantly reduced or abolished with folinic acid supplementation.A fertility study in Sprague-Dawley rats revealed no adverse effects at doses up to 16 mg/kg/day of proguanil hydrochloride (up to 0.2-times the average human exposure based on AUC comparisons.) Fertility studies of proguanil in animals at exposures similar to or greater than those observed in humans have not been conducted.Genotoxicity studies have not been performed with atovaquone in combination with proguanil. Effects of atovaquone and proguanil hydrochloride on male and female reproductive performance are unknown.. Pregnancy: Pregnancy Category C. Falciparum malaria carries higher risk of morbidity and mortality in pregnant women than in the general population. Maternal death and fetal loss are both known complications of falciparum malaria in pregnancy. In pregnant women who must travel to malaria-endemic areas, personal protection against mosquito bites should always be employed (see Information for Patients) in addition to antimalarials.Atovaquone was not teratogenic and did not cause reproductive toxicity in rats at maternal plasma concentrations up to to 6.5 times the estimated human exposure during treatment of malaria. Following single-dose administration of 14C-labeled atovaquone to pregnant rats, concentrations of radiolabel in rat fetuses were 18% (mid-gestation) and 60% (late gestation) of concurrent maternal plasma concentrations. In rabbits, atovaquone caused maternal toxicity at plasma concentrations that were approximately 0.6 to 1.3 times the estimated human exposure during treatment of malaria. Adverse fetal effects in rabbits, including decreased fetal body lengths and increased early resorptions and post-implantation losses, were observed only in the presence of maternal toxicity. Concentrations of atovaquone in rabbit fetuses averaged 30% of the concurrent maternal plasma concentrations. pre- and post-natal study in Sprague-Dawley rats revealed no adverse effects at doses up to 16 mg/kg/day of proguanil hydrochloride (up to 0.2-times the average human exposure based on AUC comparisons.) Pre- and post-natal studies of proguanil in animals at exposures similar to or greater than those observed in humans have not been conducted.The combination of atovaquone and proguanil hydrochloride was not teratogenic in rats at plasma concentrations up to 1.7 and 0.10 times, respectively, the estimated human exposure during treatment of malaria. In rabbits, the combination of atovaquone and proguanil hydrochloride was not teratogenic or embryotoxic to rabbit fetuses at plasma concentrations up to 0.34 and 0.82 times, respectively, the estimated human exposure during treatment of malaria. While there are no adequate and well-controlled studies of atovaquone and/or proguanil hydrochloride in pregnant women, atovaquone and proguanil hydrochloride may be used if the potential benefit justifies the potential risk to the fetus. The proguanil component of atovaquone and proguanil hydrochloride acts by inhibiting the parasitic dihydrofolate reductase (see CLINICAL PHARMACOLOGY: Microbiology: Mechanism of Action). However, there are no clinical data indicating that folate supplementation diminishes drug efficacy, and for women of childbearing age receiving folate supplements to prevent neural tube birth defects, such supplements may be continued while taking atovaquone and proguanil hydrochloride. Nursing Mothers: It is not known whether atovaquone is excreted into human milk. In rat study, atovaquone concentrations in the milk were 30% of the concurrent atovaquone concentrations in the maternal plasma. Proguanil is excreted into human milk in small quantities.Caution should be exercised when atovaquone and proguanil hydrochloride is administered to nursing mother.. Pediatric Use: Treatment of Malaria:. The efficacy and safety of atovaquone and proguanil hydrochloride for the treatment of malaria have been established in controlled studies involving pediatric patients weighing kg or more (see CLINICAL STUDIES). Safety and effectiveness have not been established in pediatric patients who weigh less than kg.. Prophylaxis of Malaria:. The efficacy and safety of atovaquone and proguanil hydrochloride have been established for the prophylaxis of malaria in controlled studies involving pediatric patients weighing 11 kg or more (see CLINICAL STUDIES). Safety and effectiveness have not been established in pediatric patients who weigh less than 11 kg. Geriatric Use: Clinical studies of atovaquone and proguanil hydrochloride did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. In general, dose selection for an elderly patient should be cautious, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, the higher systemic exposure to cycloguanil (see CLINICAL PHARMACOLOGY: Special Populations: Geriatrics), and the greater frequency of concomitant disease or other drug therapy.

PREGNANCY SECTION.

Pregnancy: Pregnancy Category C. Falciparum malaria carries higher risk of morbidity and mortality in pregnant women than in the general population. Maternal death and fetal loss are both known complications of falciparum malaria in pregnancy. In pregnant women who must travel to malaria-endemic areas, personal protection against mosquito bites should always be employed (see Information for Patients) in addition to antimalarials.Atovaquone was not teratogenic and did not cause reproductive toxicity in rats at maternal plasma concentrations up to to 6.5 times the estimated human exposure during treatment of malaria. Following single-dose administration of 14C-labeled atovaquone to pregnant rats, concentrations of radiolabel in rat fetuses were 18% (mid-gestation) and 60% (late gestation) of concurrent maternal plasma concentrations. In rabbits, atovaquone caused maternal toxicity at plasma concentrations that were approximately 0.6 to 1.3 times the estimated human exposure during treatment of malaria. Adverse fetal effects in rabbits, including decreased fetal body lengths and increased early resorptions and post-implantation losses, were observed only in the presence of maternal toxicity. Concentrations of atovaquone in rabbit fetuses averaged 30% of the concurrent maternal plasma concentrations. pre- and post-natal study in Sprague-Dawley rats revealed no adverse effects at doses up to 16 mg/kg/day of proguanil hydrochloride (up to 0.2-times the average human exposure based on AUC comparisons.) Pre- and post-natal studies of proguanil in animals at exposures similar to or greater than those observed in humans have not been conducted.The combination of atovaquone and proguanil hydrochloride was not teratogenic in rats at plasma concentrations up to 1.7 and 0.10 times, respectively, the estimated human exposure during treatment of malaria. In rabbits, the combination of atovaquone and proguanil hydrochloride was not teratogenic or embryotoxic to rabbit fetuses at plasma concentrations up to 0.34 and 0.82 times, respectively, the estimated human exposure during treatment of malaria. While there are no adequate and well-controlled studies of atovaquone and/or proguanil hydrochloride in pregnant women, atovaquone and proguanil hydrochloride may be used if the potential benefit justifies the potential risk to the fetus. The proguanil component of atovaquone and proguanil hydrochloride acts by inhibiting the parasitic dihydrofolate reductase (see CLINICAL PHARMACOLOGY: Microbiology: Mechanism of Action). However, there are no clinical data indicating that folate supplementation diminishes drug efficacy, and for women of childbearing age receiving folate supplements to prevent neural tube birth defects, such supplements may be continued while taking atovaquone and proguanil hydrochloride.