MECHANISM OF ACTION SECTION.

12.1 Mechanism of Action. Atropine is an antimuscarinic agent since it antagonizes the muscarine-like actions of acetylcholine and other choline esters.Atropine inhibits the muscarinic actions of acetylcholine on structures innervated by postganglionic cholinergic nerves, and on smooth muscles which respond to endogenous acetylcholine but are not so innervated. As with other antimuscarinic agents, the major action of atropine is competitive or surmountable antagonism which can be overcome by increasing the concentration of acetylcholine at receptor sites of the effector organ (e.g., by using anticholinesterase agents which inhibit the enzymatic destruction of acetylcholine). The receptors antagonized by atropine are the peripheral structures that are stimulated or inhibited by muscarine (i.e., exocrine glands and smooth and cardiac muscle). Responses to postganglionic cholinergic nerve stimulation also may be inhibited by atropine, but this occurs less readily than with responses to injected (exogenous) choline esters.

ADVERSE REACTIONS SECTION.

6 ADVERSE REACTIONS. The following adverse reactions have been identified during post-approval use of atropine sulfate. 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.Most of the side effects of atropine are directly related to its antimuscarinic action. Dryness of the mouth, blurred vision, photophobia and tachycardia commonly occur. Anhidrosis can produce heat intolerance. Constipation and difficulty in micturition may occur in elderly patients. Occasional hypersensitivity reactions have been observed, especially skin rashes which in some instances progressed to exfoliation.. Most adverse reactions are directly related to atropines antimuscarinic action. Dryness of the mouth, blurred vision, photophobia and tachycardia commonly occur with chronic administration of therapeutic doses. (6)To report SUSPECTED ADVERSE REACTIONS, contact American Regent, Inc. at 1-800-734-9236, or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

CLINICAL PHARMACOLOGY SECTION.

12 CLINICAL PHARMACOLOGY. 12.1 Mechanism of Action. Atropine is an antimuscarinic agent since it antagonizes the muscarine-like actions of acetylcholine and other choline esters.Atropine inhibits the muscarinic actions of acetylcholine on structures innervated by postganglionic cholinergic nerves, and on smooth muscles which respond to endogenous acetylcholine but are not so innervated. As with other antimuscarinic agents, the major action of atropine is competitive or surmountable antagonism which can be overcome by increasing the concentration of acetylcholine at receptor sites of the effector organ (e.g., by using anticholinesterase agents which inhibit the enzymatic destruction of acetylcholine). The receptors antagonized by atropine are the peripheral structures that are stimulated or inhibited by muscarine (i.e., exocrine glands and smooth and cardiac muscle). Responses to postganglionic cholinergic nerve stimulation also may be inhibited by atropine, but this occurs less readily than with responses to injected (exogenous) choline esters.. 12.2 Pharmacodynamics. Atropine-induced parasympathetic inhibition may be preceded by transient phase of stimulation, especially on the heart where small doses first slow the rate before characteristic tachycardia develops due to paralysis of vagal control. Atropine exerts more potent and prolonged effect on heart, intestine and bronchial muscle than scopolamine, but its action on the iris, ciliary body and certain secretory glands is weaker than that of scopolamine. Unlike the latter, atropine in clinical doses does not depress the central nervous system but may stimulate the medulla and higher cerebral centers. Although mild vagal excitation occurs, the increased respiratory rate and (sometimes) increased depth of respiration produced by atropine are more probably the result of bronchiolar dilatation. Accordingly, atropine is an unreliable respiratory stimulant and large or repeated doses may depress respiration.Adequate doses of atropine abolish various types of reflex vagal cardiac slowing or asystole. The drug also prevents or abolishes bradycardia or asystole produced by injection of choline esters, anticholinesterase agents or other parasympathomimetic drugs, and cardiac arrest produced by stimulation of the vagus. Atropine also may lessen the degree of partial heart block when vagal activity is an etiologic factor. In some patients with complete heart block, the idioventricular rate may be accelerated by atropine; in others, the rate is stabilized. Occasionally large dose may cause atrioventricular (A-V) block and nodal rhythm.Atropine Sulfate Injection, USP in clinical doses counteracts the peripheral dilatation and abrupt decrease in blood pressure produced by choline esters. However, when given by itself, atropine does not exert striking or uniform effect on blood vessels or blood pressure. Systemic doses slightly raise systolic and lower diastolic pressures and can produce significant postural hypotension. Such doses also slightly increase cardiac output and decrease central venous pressure. Occasionally, therapeutic doses dilate cutaneous blood vessels, particularly in the blush area (atropine flush), and may cause atropine fever due to suppression of sweat gland activity in infants and small children.The effects of intravenous atropine on heart rate (maximum heart rate) and saliva flow (minimum flow) after intravenous administration (rapid, constant infusion over min.) are delayed by to minutes after drug administration and both effects are non-linearly related to the amount of drug in the peripheral compartment. Changes in plasma atropine levels following intramuscular administration (0.5 to mg doses) and heart rate are closely overlapped but the time course of the changes in atropine levels and behavioral impairment indicates that pharmacokinetics is not the primary rate-limiting mechanism for the central nervous system effect of atropine.. 12.3 Pharmacokinetics. Atropine disappears rapidly from the blood following injection and is distributed throughout the body. Exercise, both prior to and immediately following intramuscular administration of atropine, significantly increases the absorption of atropine due to increased perfusion in the muscle and significantly decreases the clearance of atropine. The pharmacokinetics of atropine is nonlinear after intravenous administration of 0.5 to mg. Atropines plasma protein binding is about 44% and saturable in the to 20 mcg/mL concentration range. Atropine readily crosses the placental barrier and enters the fetal circulation, but is not found in amniotic fluid. Much of the drug is destroyed by enzymatic hydrolysis, particularly in the liver; from 13 to 50% is excreted unchanged in the urine. Traces are found in various secretions, including milk. The major metabolites of atropine are noratropine, atropin-n-oxide, tropine, and tropic acid. The metabolism of atropine is inhibited by organophosphate pesticides. Specific PopulationsThe elimination half-life of atropine is more than doubled in children under two years and the elderly (>65 years old) compared to other age groups. There is no gender effect on the pharmacokinetics and pharmacodynamics (heart rate changes) of atropine.

DESCRIPTION SECTION.

11 DESCRIPTION. Atropine Sulfate Injection, USP is sterile, nonpyrogenic isotonic solution of atropine sulfate monohydrate in water for injection with sodium chloride sufficient to render the solution isotonic. It is administered parenterally by intravenous injection.Each milliliter (mL) contains 0.4 mg or mg of atropine sulfate monohydrate equivalent to 0.332 mg or 0.83 mg of atropine, and sodium chloride, mg. May contain sodium hydroxide and/or sulfuric acid for pH adjustment. 0.308 mOsmol/mL (calc.). pH (3.0 to 5.0).The solution contains no bacteriostat, antimicrobial agent or added buffer (except for pH adjustment) and is intended for use only as single-dose injection. When smaller doses are required the unused portion should be discarded.Atropine Sulfate, USP is chemically designated H, H-Tropan-3--ol (+-)-tropate (ester), sulfate (2:1) (salt) monohydrate, (C17H23NO3)2 H2SO4 H2O, colorless crystals or white crystalline powder very soluble in water. It has the following structural formula:Atropine, naturally occurring belladonna alkaloid, is racemic mixture of equal parts of d- and 1-hyocyamine, whose activity is due almost entirely to the levo isomer of the drug.. structural formula atropine sulfate.

DOSAGE & ADMINISTRATION SECTION.

2 DOSAGE AND ADMINISTRATION. For intravenous administration. (2.1).Titrate according to heart rate, PR interval, blood pressure and symptoms. (2.1)Adult dosageAntisialagogue or for antivagal effects: Initial single dose of 0.5 to mg. (2.2)Antidote for organophosphorus or muscarinic mushroom poisoning: Initial single dose of to mg, repeated every 20 to 30 minutes. (2.2)Bradyasystolic cardiac arrest: mg dose, repeated every to minutes if asystole persists. (2.2) Patients with Coronary Artery Disease: Limit the total dose to 0.03 mg/kg to 0.04 mg/kg. (2.4). For intravenous administration. (2.1).. Titrate according to heart rate, PR interval, blood pressure and symptoms. (2.1). Adult dosageAntisialagogue or for antivagal effects: Initial single dose of 0.5 to mg. (2.2)Antidote for organophosphorus or muscarinic mushroom poisoning: Initial single dose of to mg, repeated every 20 to 30 minutes. (2.2)Bradyasystolic cardiac arrest: mg dose, repeated every to minutes if asystole persists. (2.2) Antisialagogue or for antivagal effects: Initial single dose of 0.5 to mg. (2.2). Antidote for organophosphorus or muscarinic mushroom poisoning: Initial single dose of to mg, repeated every 20 to 30 minutes. (2.2). Bradyasystolic cardiac arrest: mg dose, repeated every to minutes if asystole persists. (2.2). Patients with Coronary Artery Disease: Limit the total dose to 0.03 mg/kg to 0.04 mg/kg. (2.4). 2.1 General Administration. Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit. Do not administer unless solution is clear and seal is intact. Each vial is intended for single dose only. Discard unused portion.For Intravenous administration.Titrate based on heart rate, PR interval, blood pressure and symptoms.. 2.2 Adult Dosage. Table 1: Recommended DosageUseDose (adults)RepeatAntisialagogue or other antivagal0.5 to mg1 to hoursOrganophosphorus or muscarinic mushroom poisoning2 to mg20 to 30 minutesBradyasystolic cardiac arrest1 mg3 to minutes; mg maximum total dose. 2.3 Pediatric Dosage. Dosing in pediatric populations has not been well studied. Usual initial dose is 0.01 to 0.03 mg/kg.. 2.4 Dosing in Patients with Coronary Artery Disease. Limit the total dose of atropine sulfate to 0.03 to 0.04 mg/kg [see Warnings and Precautions (5.1)].

OVERDOSAGE SECTION.

10 OVERDOSAGE. Excessive dosing may cause palpitation, dilated pupils, difficulty in swallowing, hot dry skin, thirst, dizziness, restlessness, tremor, fatigue and ataxia. Toxic doses lead to restlessness and exctextent, hallucinations, delirium and coma. Depression and circulatory collapse occur only with severe intoxication. In such cases, blood pressure declines and death due to respiratory failure may ensue following paralysis and coma.The fatal adult dose of atropine is not known. In pediatric populations, 10 mg or less may be fatal.In the event of toxic overdosage, short acting barbiturate or diazepam may be given as needed to control marked exctextent and convulsions. Large doses for sedation should be avoided because central depressant action may coincide with the depression occurring late in atropine poisoning. Central stimulants are not recommended. Physostigmine, given as an atropine antidote by slow intravenous injection of to mg (0.5 to mg in pediatric populations), rapidly abolishes delirium and coma caused by large doses of atropine. Since physostigmine is rapidly destroyed, the patient may again lapse into coma after one to two hours, and repeated doses may be required. Artificial respiration with oxygen may be necessary. Ice bags and alcohol sponges help to reduce fever, especially in pediatric populations.Atropine is not removed by dialysis.

PHARMACODYNAMICS SECTION.

12.2 Pharmacodynamics. Atropine-induced parasympathetic inhibition may be preceded by transient phase of stimulation, especially on the heart where small doses first slow the rate before characteristic tachycardia develops due to paralysis of vagal control. Atropine exerts more potent and prolonged effect on heart, intestine and bronchial muscle than scopolamine, but its action on the iris, ciliary body and certain secretory glands is weaker than that of scopolamine. Unlike the latter, atropine in clinical doses does not depress the central nervous system but may stimulate the medulla and higher cerebral centers. Although mild vagal excitation occurs, the increased respiratory rate and (sometimes) increased depth of respiration produced by atropine are more probably the result of bronchiolar dilatation. Accordingly, atropine is an unreliable respiratory stimulant and large or repeated doses may depress respiration.Adequate doses of atropine abolish various types of reflex vagal cardiac slowing or asystole. The drug also prevents or abolishes bradycardia or asystole produced by injection of choline esters, anticholinesterase agents or other parasympathomimetic drugs, and cardiac arrest produced by stimulation of the vagus. Atropine also may lessen the degree of partial heart block when vagal activity is an etiologic factor. In some patients with complete heart block, the idioventricular rate may be accelerated by atropine; in others, the rate is stabilized. Occasionally large dose may cause atrioventricular (A-V) block and nodal rhythm.Atropine Sulfate Injection, USP in clinical doses counteracts the peripheral dilatation and abrupt decrease in blood pressure produced by choline esters. However, when given by itself, atropine does not exert striking or uniform effect on blood vessels or blood pressure. Systemic doses slightly raise systolic and lower diastolic pressures and can produce significant postural hypotension. Such doses also slightly increase cardiac output and decrease central venous pressure. Occasionally, therapeutic doses dilate cutaneous blood vessels, particularly in the blush area (atropine flush), and may cause atropine fever due to suppression of sweat gland activity in infants and small children.The effects of intravenous atropine on heart rate (maximum heart rate) and saliva flow (minimum flow) after intravenous administration (rapid, constant infusion over min.) are delayed by to minutes after drug administration and both effects are non-linearly related to the amount of drug in the peripheral compartment. Changes in plasma atropine levels following intramuscular administration (0.5 to mg doses) and heart rate are closely overlapped but the time course of the changes in atropine levels and behavioral impairment indicates that pharmacokinetics is not the primary rate-limiting mechanism for the central nervous system effect of atropine.

PHARMACOKINETICS SECTION.

12.3 Pharmacokinetics. Atropine disappears rapidly from the blood following injection and is distributed throughout the body. Exercise, both prior to and immediately following intramuscular administration of atropine, significantly increases the absorption of atropine due to increased perfusion in the muscle and significantly decreases the clearance of atropine. The pharmacokinetics of atropine is nonlinear after intravenous administration of 0.5 to mg. Atropines plasma protein binding is about 44% and saturable in the to 20 mcg/mL concentration range. Atropine readily crosses the placental barrier and enters the fetal circulation, but is not found in amniotic fluid. Much of the drug is destroyed by enzymatic hydrolysis, particularly in the liver; from 13 to 50% is excreted unchanged in the urine. Traces are found in various secretions, including milk. The major metabolites of atropine are noratropine, atropin-n-oxide, tropine, and tropic acid. The metabolism of atropine is inhibited by organophosphate pesticides. Specific PopulationsThe elimination half-life of atropine is more than doubled in children under two years and the elderly (>65 years old) compared to other age groups. There is no gender effect on the pharmacokinetics and pharmacodynamics (heart rate changes) of atropine.

PREGNANCY SECTION.

8.1 Pregnancy. PregnancyRisk SummaryThere are risks to the mother and fetus associated with untreated severe or life-threatening muscarinic events (see Clinical Considerations). Available data from published observational studies on atropine use in pregnant women are insufficient to evaluate for drug-associated risk of major birth defects, miscarriage, or adverse maternal or fetal outcomes (see Data). Animal reproduction studies have not been conducted with atropine. Clinical ConsiderationsDisease-associated maternal and/or embryo/fetal risk Severe or life-threatening muscarinic events such as acute organophosphate poisoning and symptomatic bradycardia are medical emergencies in pregnancy which can be fatal if left untreated. Life-sustaining therapy for the pregnant woman should not be withheld because of concerns regarding the effects of atropine on the fetus. DataHuman Data Atropine crosses the placenta [see Clinical Pharmacology (12.3)]. No adequate and well-controlled studies are available regarding use of atropine in pregnant women. In cohort study of 401 pregnancies in the first trimester and 797 pregnancies in the second or third trimester, atropine use was not associated with an increased risk of congenital malformation. In surveillance study, 381 newborns were exposed to atropine during the first trimester; 18 major birth defects were observed when 16 were expected. No specific pattern of major birth defects was identified. In another surveillance study of 50 pregnancies in the first trimester, atropine use was not associated with an increased risk of malformations. Methodological limitations of these observational studies including the inability to control for the dosage and timing of atropine exposure, underlying maternal disease, or concomitant maternal drug use, cannot definitively establish or exclude any drug associated risk during pregnancy.

USE IN SPECIFIC POPULATIONS SECTION.

8 USE IN SPECIFIC POPULATIONS. 8.1 Pregnancy. PregnancyRisk SummaryThere are risks to the mother and fetus associated with untreated severe or life-threatening muscarinic events (see Clinical Considerations). Available data from published observational studies on atropine use in pregnant women are insufficient to evaluate for drug-associated risk of major birth defects, miscarriage, or adverse maternal or fetal outcomes (see Data). Animal reproduction studies have not been conducted with atropine. Clinical ConsiderationsDisease-associated maternal and/or embryo/fetal risk Severe or life-threatening muscarinic events such as acute organophosphate poisoning and symptomatic bradycardia are medical emergencies in pregnancy which can be fatal if left untreated. Life-sustaining therapy for the pregnant woman should not be withheld because of concerns regarding the effects of atropine on the fetus. DataHuman Data Atropine crosses the placenta [see Clinical Pharmacology (12.3)]. No adequate and well-controlled studies are available regarding use of atropine in pregnant women. In cohort study of 401 pregnancies in the first trimester and 797 pregnancies in the second or third trimester, atropine use was not associated with an increased risk of congenital malformation. In surveillance study, 381 newborns were exposed to atropine during the first trimester; 18 major birth defects were observed when 16 were expected. No specific pattern of major birth defects was identified. In another surveillance study of 50 pregnancies in the first trimester, atropine use was not associated with an increased risk of malformations. Methodological limitations of these observational studies including the inability to control for the dosage and timing of atropine exposure, underlying maternal disease, or concomitant maternal drug use, cannot definitively establish or exclude any drug associated risk during pregnancy. 8.2 Lactation. Risk Summary Trace amounts of atropine have been reported in human milk after oral intake. There are no available data on atropine levels in human milk after intravenous injection, the effects on the breastfed infant, or the effects on milk production.Clinical ConsiderationsMinimizing exposure The elimination half-life of atropine is more than doubled in children less than years of age [see Clinical Pharmacology (12.3)]. To minimize potential infant exposure to Atropine Sulfate Injection, woman may pump and discard her milk for 24 hours after use before resuming to breastfeed her infant.. 8.4 Pediatric Use. Recommendations for use in pediatric patients are not based on clinical trials.. 8.5 Geriatric Use. An evaluation of current literature revealed no clinical experience identifying differences in response between elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.