ADVERSE REACTIONS SECTION.

6 ADVERSE REACTIONS. The following serious adverse reactions are described elsewhere in labeling:Hypersensitivity and Other Life-Threatening Reactions [see Warnings and Precautions (5.1)] Hypokalemia [see Warnings and Precautions (5.3)] Metabolic Acidosis [see Warnings and Precautions (5.4)] Falls [see Warnings and Precautions (5.5)] Hypersensitivity and Other Life-Threatening Reactions [see Warnings and Precautions (5.1)] Hypokalemia [see Warnings and Precautions (5.3)] Metabolic Acidosis [see Warnings and Precautions (5.4)] Falls [see Warnings and Precautions (5.5)] Most common adverse reactions (incidence at least 10% and greater than placebo) include paresthesias, cognitive disorder, dysgeusia, and confusional state (6.1)To report SUSPECTED ADVERSE REACTIONS, contact Xeris Pharmaceuticals, Inc. at 1-855-324-8912, or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience. Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.In 9-week randomized controlled trial in adults with hyperkalemic or hypokalemic periodic paralysis (Study 1), the most common adverse reactions in patients treated with dichlorphenamide tablets, with rates greater than placebo, were paresthesia, cognitive disorder, dysgeusia, and confusional state. The mean dose of dichlorphenamide tablets was 94 mg/day in patients with hypokalemic periodic paralysis and 82 mg/day in patients with hyperkalemic periodic paralysis.Table lists the incidence of adverse reactions that occurred in >= 5% of patients treated with dichlorphenamide tablets and more commonly than in patients treated with placebo in Study 1.Table 1: Adverse Reactions in Patients Treated with Dichlorphenamide Tablets with Incidence >= 5% and more common than in Patients Treated with Placebo in Study 1Adverse ReactionDichlorphenamide TabletsN 36 (%)Placebo = 29 (%)Nervous system disordersParesthesia4414Cognitive disorder Cognitive disorder combined cases with the preferred terms of cognitive disorder, disturbance in attention, and mental impairment. 147Dysgeusia140Confusional state110Headache87Hypoesthesia80Lethargy80Dizziness60Gastrointestinal disordersDiarrhea63Nausea60General disorders and administration site conditionsFatigue80Malaise60InvestigationsWeight decreased60Musculoskeletal and connective tissue disordersMuscle spasms80Arthralgia63Muscle twitching60RespiratoryDyspnea60Pharyngolaryngeal pain60SkinRash80Pruritus60. 6.2 Postmarketing Experience. Adverse reactions have been identified during postapproval use of dichlorphenamide. Because these reactions are reported voluntarily from population of uncertain size, it is not always possible to reliably estimate their frequency or establish causal relationship to drug exposure.The following are adverse reactions which have been reported during postapproval use of dichlorphenamide and were serious or are not reported in the previous section of labeling [see Clinical Trials Experience (6.1)] amnesia, cardiac failure, condition aggravated, convulsion, hallucination, nephrolithiasis, pancytopenia, psychotic disorder, renal tubular necrosis, stupor, syncope, tremor.

CLINICAL PHARMACOLOGY SECTION.

12 CLINICAL PHARMACOLOGY. 12.1 Mechanism of Action. Dichlorphenamide is carbonic anhydrase inhibitor. However, the precise mechanism by which dichlorphenamide exerts its therapeutic effects in patients with primary periodic paralysis is unknown.. 12.2 Pharmacodynamics. Dichlorphenamide can cause metabolic acidosis, which can increase the risk of salicylate toxicity with coadministration [see Warnings and Precautions (5.2)]. Dichlorphenamide-induced metabolic acidosis can also increase in severity with coadministration of other drugs that cause metabolic acidosis [see Warnings and Precautions (5.4)]. 12.3 Pharmacokinetics. After single-dose administration in healthy subjects in fasted state, dichlorphenamide Cmax and AUC increased in dose-proportional manner within the range of 25 mg to 400 mg (2 times the maximum recommended dose). The steady-state is expected to be achieved within 10 days of twice-daily dosing.AbsorptionThe median time to reach maximum concentration (Tmax) of dichlorphenamide was about 1.5 to hours postdose after both single and multiple dose administrations.DistributionThe plasma protein binding of dichlorphenamide is approximately 88%.EliminationFollowing single-dose administration, mean terminal half-life was in the range of 32 to 66 hours.MetabolismDichlorphenamide is not substrate for CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6 and CYP3A4 isoforms when tested in vitro.Drug Interaction StudiesIn vitro Assessment of Drug InteractionsDrug-Metabolizing Enzyme InhibitionDichlorphenamide is not an inhibitor for CYP1A2, 2B6, 2C8, 2C9, 2C19, 2D6, or 3A4 enzymes when tested in vitro.Drug-Metabolizing Enzyme InductionDichlorphenamide is not an inducer for CYP1A2, 2B6, or 3A4 enzymes when tested in vitro.In vitro Assessment of Transporter-Drug InteractionsDichlorphenamide is neither substrate nor inhibitor for p-gp, BCRP, OATP1B1, OATP1B3, OAT2, OAT4, OCT1, OCT2, MATE1, or MATE2-K when tested in vitro.Dichlorphenamide is not an inhibitor of OAT3, but is an inhibitor of OAT1 based on in vitro studies [see Drug Interactions (7.4)]. Dichlorphenamide is substrate for transporters OAT1 and OAT3 based on in vitro studies [see Drug Interactions (7.2)].In Vivo Drug InteractionsThe use of dichlorphenamide in combination with high-dose aspirin is contraindicated as it may lead to salicylate toxicity. The mechanism(s) of this interaction is not known.Specific PopulationsGeriatricsThe pharmacokinetics of dichlorphenamide in the elderly has not been determined.

CLINICAL STUDIES SECTION.

14 CLINICAL STUDIES. The efficacy of dichlorphenamide tablets was evaluated in two clinical studies, Study and Study 2.. Study 1Study was 9-week, double blind, placebo-controlled multi-center study. Study consisted of two substudies: substudy in patients with hypokalemic periodic paralysis (n=44), and substudy in patients with hyperkalemic periodic paralysis (n=21). The primary efficacy endpoint in both substudies was the average number of self-reported attacks of muscle weakness per week over the final weeks of the trial. Withdrawal from the study for acute severe worsening (increase in attack frequency or severity) was also assessed as an endpoint.In Study 1, the dose of dichlorphenamide tablets was 50 mg b.i.d. for treatment-naive patients. Patients already on dichlorphenamide prior to the study continued on the same dose while on dichlorphenamide tablets during the study. In patients taking acetazolamide prior to the study, the dose of dichlorphenamide tablets was set at 20% of the acetazolamide dose. Dose reduction for tolerability was permitted.. Hypokalemic Periodic Paralysis Substudy of Study 1In the hypokalemic periodic paralysis substudy, median age of patients was 45 years and 73% of patients were male. Patients treated with dichlorphenamide tablets (n=24) had 2.2 fewer attacks per week than patients (n=20) treated with placebo (p=0.02). None of the patients randomized to dichlorphenamide tablets reached the endpoint of withdrawal from the study for acute worsening, vs. five patients randomized to placebo. The mean dose of dichlorphenamide tablets at Week was 94 mg/day.. Hyperkalemic Periodic Paralysis Substudy of Study 1In the Hyperkalemic Periodic Paralysis substudy, median age of patients was 43 years and 43% of patients were male. During the double-blind treatment period, patients treated with dichlorphenamide tablets (n=12) had 3.9 fewer attacks per week than patients (n=9) treated with placebo (p=0.08). None of the patients randomized to dichlorphenamide tablets reached the endpoint of withdrawal from the study for acute worsening, vs. two patients randomized to placebo. The mean dose of dichlorphenamide tablets at Week was 82 mg/day.. Study 2Study was 35-week, double blind, placebo-controlled, multi-center, two-period crossover study. Study also consisted of two substudies: substudy in patients with hypokalemic periodic paralysis (n=42), and substudy in patients with hyperkalemic periodic paralysis (n=31), including patients with Paramyotonia Congenita. The primary endpoint in the hypokalemic periodic paralysis substudy was the incidence of acute intolerable worsening (based on attack frequency or severity) necessitating withdrawal. The primary endpoint in the hyperkalemic periodic paralysis substudy was the average number of self-reported attacks of muscle weakness per week. Dosing was determined similarly to Study 1.. Hypokalemic Periodic Paralysis Substudy of Study 2The hypokalemic periodic paralysis substudy included patients with mean age of 38 years; 79% of patients were male. Acute intolerable worsening was observed in patients on dichlorphenamide tablets vs. 11 patients on placebo (p=0.02). The mean dose of dichlorphenamide tablets at the end of the study was 96 mg/day.. Hyperkalemic Periodic Paralysis Substudy of Study 2The hyperkalemic periodic paralysis substudy included patients with mean age of 37 years; and 79% of patients were male. Patients treated had 2.3 fewer attacks per week on dichlorphenamide tablets than on placebo (p=0.006). The mean dose of dichlorphenamide tablets at the end of the study was 73 mg/day.

CONTRAINDICATIONS SECTION.

4 CONTRAINDICATIONS. Dichlorphenamide is contraindicated in the following circumstances:Hypersensitivity to dichlorphenamide or other sulfonamides [see Warnings and Precautions (5.1)] Concomitant use of dichlorphenamide tablets and high dose aspirin [see Warnings and Precautions (5.2) and Drug Interactions (7.1)] Severe pulmonary disease, limiting compensation to metabolic acidosis caused by dichlorphenamide [see Warnings and Precautions (5.4)] Hepatic insufficiency: Dichlorphenamide may aggravate hepatic encephalopathy.. Hypersensitivity to dichlorphenamide or other sulfonamides [see Warnings and Precautions (5.1)] Concomitant use of dichlorphenamide tablets and high dose aspirin [see Warnings and Precautions (5.2) and Drug Interactions (7.1)] Severe pulmonary disease, limiting compensation to metabolic acidosis caused by dichlorphenamide [see Warnings and Precautions (5.4)] Hepatic insufficiency: Dichlorphenamide may aggravate hepatic encephalopathy.. Hepatic insufficiency (4)Severe pulmonary obstruction (4)Hypersensitivity to dichlorphenamide or other sulfonamides (4)Concomitant use with high dose aspirin (4). Hepatic insufficiency (4). Severe pulmonary obstruction (4). Hypersensitivity to dichlorphenamide or other sulfonamides (4). Concomitant use with high dose aspirin (4).

DESCRIPTION SECTION.

11 DESCRIPTION. Dichlorphenamide tablets contain dichlorphenamide, an oral carbonic anhydrase inhibitor. Dichlorphenamide, dichlorinated benzenedisulfonamide, is known chemically as 4, 5-dichloro-1,3-benzenedisulfonamide.Its empirical formula is C6H6Cl2N2O4S2 and its structural formula is:Dichlorphenamide USP is white or practically white, crystalline compound with molecular weight of 305.16. It is very slightly soluble in water but soluble in dilute solutions of sodium carbonate and sodium hydroxide. Dilute alkaline solutions of dichlorphenamide are stable at room temperature.Dichlorphenamide tablets are supplied as tablets, for oral administration, each containing 50 mg dichlorphenamide. Inactive ingredients are lactose monohydrate, magnesium stearate and pregelatinized starch.. Chemical Structure.

DOSAGE & ADMINISTRATION SECTION.

2 DOSAGE AND ADMINISTRATION. Initiate dosing at 50 mg by mouth once or twice daily (2.1)Titrate up or down dose based on individual response (2.1)The minimum recommended dosage is 50 mg daily, and the maximum recommended dosage is 200 mg daily (2.1)Evaluate response to dichlorphenamide tablets after months of treatment (2.2). Initiate dosing at 50 mg by mouth once or twice daily (2.1). Titrate up or down dose based on individual response (2.1). The minimum recommended dosage is 50 mg daily, and the maximum recommended dosage is 200 mg daily (2.1). Evaluate response to dichlorphenamide tablets after months of treatment (2.2). 2.1 Dosage Information. Initiate dosing at 50 mg by mouth once or twice daily. The dosage may be increased or decreased based on individual response, at weekly intervals (or sooner in case of adverse reaction). The minimum recommended total daily dosage is 50 mg, and the maximum recommended total daily dosage is 200 mg.. 2.2 Monitoring to Assess Effectiveness. Primary hyperkalemic periodic paralysis, primary hypokalemic periodic paralysis, and related variants are heterogeneous group of conditions, for which the response to dichlorphenamide tablets may vary. Therefore, prescribers should evaluate the patients response to dichlorphenamide tablets after months of treatment to decide whether dichlorphenamide tablets should be continued.. 2.3 Monitoring to Assess Safety. Baseline and periodic measurements of serum potassium and serum bicarbonate during dichlorphenamide tablets treatment is recommended [see Warnings and Precautions (5.3, 5.4)].

DRUG INTERACTIONS SECTION.

7 DRUG INTERACTIONS. Aspirin: anorexia, tachypnea, lethargy, and coma have been reported with concomitant use of dichlorphenamide and high-dose aspirin. The concomitant use of dichlorphenamide tablets and high-dose aspirin is contraindicated. Dichlorphenamide tablets should be used with caution in patients receiving lower doses of aspirin (4, 5.2, 7.1). 7.1 Aspirin and Other Salicylates. Carbonic anhydrase inhibitors, including dichlorphenamide, can cause metabolic acidosis [see Warnings and Precautions 5.2, 5.4 )], which can increase the risk of salicylate toxicity. Anorexia, tachypnea, lethargy, and coma have been reported with concomitant use of dichlorphenamide and high-dose aspirin. Therefore, concomitant use of dichlorphenamide tablets and high-dose aspirin is contraindicated. Patients with concomitant use of dichlorphenamide tablets and low-dose aspirin should be carefully monitored [see Contraindications (4) and Warnings and Precautions (5.2)]. 7.2 Drugs that are Substrates of Organic Anion Transporter1 (OAT1). In vitro, dichlorphenamide is an inhibitor of OAT1 transporters. The concomitant administration of dichlorphenamide tablets may increase the plasma exposures of OAT1 substrates. Use of dichlorphenamide tablets with drugs that are sensitive to OAT1 inhibition (e.g., methotrexate, famotidine, oseltamivir) is not recommended [see Clinical Pharmacology (12.3)]. 7.3 Drugs that Cause Hypokalemia. The risk of hypokalemia is greater with coadministration of dichlorphenamide and other drugs that can cause hypokalemia (e.g., loop diuretics, thiazide diuretics, laxatives, antifungals, penicillins, and theophylline) [see Warnings and Precautions (5.3)] .. 7.4 Drugs that Cause Metabolic Acidosis. Coadministration of dichlorphenamide and other drugs that can cause metabolic acidosis may increase the severity of the acidosis [see Warnings and Precautions (5.4)]. 7.5 Drugs that are Inhibitors of OAT1 or OAT3. An in vitro transporter study indicated that dichlorphenamide is substrate of human transporters OAT1 and OAT3 [see Clinical Pharmacology (12.3)] Therefore, signs of dichlorphenamide toxicity should be monitored when administered with OAT1 or OAT3 inhibitors.

INFORMATION FOR PATIENTS SECTION.

17 PATIENT COUNSELING INFORMATION. Worsening of SymptomsAdvise patients to notify their physician if they experience acute worsening of symptoms of periodic paralysis.Hypersensitivity and Other Life-Threatening ReactionsInform patients that hypersensitivity and immune mediated reactions can occur with dichlorphenamide tablets, and could be fatal. Advise patients to discontinue dichlorphenamide tablets and notify their healthcare provider immediately if they develop rash or signs and symptoms of anaphylaxis or other life-threatening reactions [see Warnings and Precautions (5.1)]. Drug InteractionsInstruct patients to notify their healthcare provider of all of the drugs and over-the-counter medications that they take and to not take aspirin or other salicylates without first discussing with their healthcare provider [see Drug Interactions (7.1, 7.2, 7.3, 7.4)]. Metabolic AcidosisInstruct patients to contact their healthcare provider immediately if they develop possible manifestations of metabolic acidosis (e.g., fast breathing, fatigue/tiredness, loss of appetite, or irregular heart beat or palpitations) [see Warnings and Precautions (5.4)]. FallsInform patients that dichlorphenamide tablets can increase their risk of falls [see Warnings and Precautions (5.5)]. Cognitive ImpairmentAdvise patients to notify their healthcare provider if they experience symptoms of cognitive impairment including confusion and memory lapse [see Adverse Reactions (6.1)]. Driving and Operating MachineryDichlorphenamide tablets may cause drowsiness/fatigue in some patients [see Adverse Reactions (6.1)]. Caution patients on the potential for impaired ability to drive and operate machinery.

PHARMACOKINETICS SECTION.

12.3 Pharmacokinetics. After single-dose administration in healthy subjects in fasted state, dichlorphenamide Cmax and AUC increased in dose-proportional manner within the range of 25 mg to 400 mg (2 times the maximum recommended dose). The steady-state is expected to be achieved within 10 days of twice-daily dosing.AbsorptionThe median time to reach maximum concentration (Tmax) of dichlorphenamide was about 1.5 to hours postdose after both single and multiple dose administrations.DistributionThe plasma protein binding of dichlorphenamide is approximately 88%.EliminationFollowing single-dose administration, mean terminal half-life was in the range of 32 to 66 hours.MetabolismDichlorphenamide is not substrate for CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6 and CYP3A4 isoforms when tested in vitro.Drug Interaction StudiesIn vitro Assessment of Drug InteractionsDrug-Metabolizing Enzyme InhibitionDichlorphenamide is not an inhibitor for CYP1A2, 2B6, 2C8, 2C9, 2C19, 2D6, or 3A4 enzymes when tested in vitro.Drug-Metabolizing Enzyme InductionDichlorphenamide is not an inducer for CYP1A2, 2B6, or 3A4 enzymes when tested in vitro.In vitro Assessment of Transporter-Drug InteractionsDichlorphenamide is neither substrate nor inhibitor for p-gp, BCRP, OATP1B1, OATP1B3, OAT2, OAT4, OCT1, OCT2, MATE1, or MATE2-K when tested in vitro.Dichlorphenamide is not an inhibitor of OAT3, but is an inhibitor of OAT1 based on in vitro studies [see Drug Interactions (7.4)]. Dichlorphenamide is substrate for transporters OAT1 and OAT3 based on in vitro studies [see Drug Interactions (7.2)].In Vivo Drug InteractionsThe use of dichlorphenamide in combination with high-dose aspirin is contraindicated as it may lead to salicylate toxicity. The mechanism(s) of this interaction is not known.Specific PopulationsGeriatricsThe pharmacokinetics of dichlorphenamide in the elderly has not been determined.

PREGNANCY SECTION.

8.1 Pregnancy. Risk SummaryThere are no adequate data on the developmental risk associated with the use of dichlorphenamide in pregnant women. no-effect dose has not been established. Dichlorphenamide was teratogenic when administered orally to pregnant rats.The background risk of major birth defects and miscarriage for the indicated population is unknown. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4%, and 15% to 20%, respectively.Clinical ConsiderationsFetal/Neonatal adverse reactionsDichlorphenamide treatment can cause metabolic acidosis [see Warnings and Precautions (5.4)]. The effect of dichlorphenamide-induced metabolic acidosis has not been studied in pregnancy; however, metabolic acidosis in pregnancy (due to other causes) can cause decreased fetal growth, decreased fetal oxygenation, and fetal death, and may affect the fetus ability to tolerate labor. Pregnant patients should be monitored for metabolic acidosis and treated as in the nonpregnant state. Newborns of mothers treated with dichlorphenamide should be monitored for metabolic acidosis because of possible occurrence of transient metabolic acidosis following birth.Labor or DeliveryAlthough the effect of dichlorphenamide on labor and delivery in humans has not been established, the development of dichlorphenamide-induced metabolic acidosis in the mother and/or in the fetus might affect the fetus ability to tolerate labor. DataAnimal DataTeratogenic effects (fetal limb reduction defects) were reported following oral administration of dichlorphenamide to pregnant rats during organogenesis at 350 mg/kg, or 17 times the maximum recommended human dose (200 mg/day) on body surface area (mg/m2) basis. no-effect dose for adverse effects on embryofetal development has not been established.

USE IN SPECIFIC POPULATIONS SECTION.

8 USE IN SPECIFIC POPULATIONS. Pregnancy: Based on animal data, may cause fetal harm (8.1). 8.1 Pregnancy. Risk SummaryThere are no adequate data on the developmental risk associated with the use of dichlorphenamide in pregnant women. no-effect dose has not been established. Dichlorphenamide was teratogenic when administered orally to pregnant rats.The background risk of major birth defects and miscarriage for the indicated population is unknown. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4%, and 15% to 20%, respectively.Clinical ConsiderationsFetal/Neonatal adverse reactionsDichlorphenamide treatment can cause metabolic acidosis [see Warnings and Precautions (5.4)]. The effect of dichlorphenamide-induced metabolic acidosis has not been studied in pregnancy; however, metabolic acidosis in pregnancy (due to other causes) can cause decreased fetal growth, decreased fetal oxygenation, and fetal death, and may affect the fetus ability to tolerate labor. Pregnant patients should be monitored for metabolic acidosis and treated as in the nonpregnant state. Newborns of mothers treated with dichlorphenamide should be monitored for metabolic acidosis because of possible occurrence of transient metabolic acidosis following birth.Labor or DeliveryAlthough the effect of dichlorphenamide on labor and delivery in humans has not been established, the development of dichlorphenamide-induced metabolic acidosis in the mother and/or in the fetus might affect the fetus ability to tolerate labor. DataAnimal DataTeratogenic effects (fetal limb reduction defects) were reported following oral administration of dichlorphenamide to pregnant rats during organogenesis at 350 mg/kg, or 17 times the maximum recommended human dose (200 mg/day) on body surface area (mg/m2) basis. no-effect dose for adverse effects on embryofetal development has not been established.. 8.2 Lactation. Risk SummaryThere are no data on the presence of dichlorphenamide in human milk, the effects on the breastfed infant, or the effects on milk production. The developmental and health benefits of breastfeeding should be considered along with the mothers clinical need for dichlorphenamide and any potential adverse effects on the breastfed infant from dichlorphenamide or from the underlying maternal condition.. 8.4 Pediatric Use. Safety and effectiveness of dichlorphenamide tablets in pediatric patients have not been established.. 8.5 Geriatric Use. The risk of falls and of metabolic acidosis are greater in elderly patients [see Warnings and Precautions (5.4, 5.5)].

WARNINGS AND PRECAUTIONS SECTION.

5 WARNINGS AND PRECAUTIONS. Hypersensitivity and Other Life-Threatening Reactions: discontinue dichlorphenamide tablets at the first appearance of skin rash or any sign of immune-mediated or idiosyncratic adverse reaction (5.1)Hypokalemia: baseline and periodic measurements of serum potassium are recommended; if hypokalemia develops or persists, consider reducing the dose or discontinuing dichlorphenamide tablets and correcting potassium levels (5.3)Metabolic acidosis: baseline and periodic measurements of serum bicarbonate are recommended; if metabolic acidosis develops or persists, consider reducing the dose or discontinuing dichlorphenamide tablets (5.4)Falls: consider reducing the dose or discontinuing dichlorphenamide tablets in patients who experience falls (5.5). Hypersensitivity and Other Life-Threatening Reactions: discontinue dichlorphenamide tablets at the first appearance of skin rash or any sign of immune-mediated or idiosyncratic adverse reaction (5.1). Hypokalemia: baseline and periodic measurements of serum potassium are recommended; if hypokalemia develops or persists, consider reducing the dose or discontinuing dichlorphenamide tablets and correcting potassium levels (5.3). Metabolic acidosis: baseline and periodic measurements of serum bicarbonate are recommended; if metabolic acidosis develops or persists, consider reducing the dose or discontinuing dichlorphenamide tablets (5.4). Falls: consider reducing the dose or discontinuing dichlorphenamide tablets in patients who experience falls (5.5). 5.1 Hypersensitivity and Other Life-Threatening Reactions. Fatalities associated with the administration of sulfonamides have occurred because of adverse reactions including Stevens-Johnson syndrome, toxic epidermal necrolysis, fulminant hepatic necrosis, agranulocytosis, aplastic anemia and other blood dyscrasias. Pulmonary involvement can occur in isolation or as part of systemic reaction.Dichlorphenamide tablets should be discontinued at the first appearance of skin rash or any sign of immune-mediated or other life-threatening adverse reaction.. 5.2 Concomitant Use of Aspirin or Other Salicylates. Carbonic anhydrase inhibitors, including dichlorphenamide, can cause metabolic acidosis [see Warnings and Precautions (5.4)] which can increase the risk of salicylate toxicity. Anorexia, tachypnea, lethargy, and coma have been reported with concomitant use of dichlorphenamide and high-dose aspirin. Therefore, the concomitant use of dichlorphenamide tablets and high-dose aspirin is contraindicated. Patients with concomitant use of dichlorphenamide tablets and low-dose aspirin should be carefully monitored.. 5.3 Hypokalemia. Dichlorphenamide increases potassium excretion and can cause hypokalemia. The risk of hypokalemia is greater when dichlorphenamide is used in patients with conditions associated with hypokalemia (e.g., adrenocortical excess, renal tubular acidosis type and 2), and in patients receiving other drugs that may cause hypokalemia [see Drug Interactions (7.3)].Baseline and periodic measurements of serum potassium during dichlorphenamide treatment is recommended.If hypokalemia develops or persists, consideration should be given to reducing the dose or discontinuing dichlorphenamide tablets and correction of potassium levels.. 5.4 Metabolic Acidosis. Dichlorphenamide can cause hyperchloremic non-anion gap metabolic acidosis. Concomitant use of dichlorphenamide with other drugs that cause metabolic acidosis may increase the severity of acidosis. Concomitant use of dichlorphenamide tablets in compensated patients with respiratory acidosis, such as in advanced lung diseases, may lead to respiratory decompensation.Baseline and periodic measurements of serum bicarbonate during dichlorphenamide treatment is recommended.If metabolic acidosis develops or persists, consideration should be given to reducing the dose or discontinuing dichlorphenamide tablets [see Drug Interactions (7.4)]. 5.5 Falls. Dichlorphenamide increases the risk of falls. The risk of falls is greater in the elderly and with higher doses of dichlorphenamide. Consider dose reduction or discontinuation of dichlorphenamide tablets in patients who experience falls while treated with dichlorphenamide.