Pyridostigmine Bromide

Pyridostigmine bromide is indicated for pretreatment against the lethal effects of soman nerve agent poisoning in adults. Pyridostigmine bromide is intended for use in conjunction with protective garments, including a mask. At the first sign of nerve agent poisoning, pyridostigmine bromide should be stopped, and atropine and pralidoxime therapy started immediately. The evidence for the effectiveness of pyridostigmine bromide as pretreatment against soman-induced toxicity was derived from animal studies alone [see Clinical Studies (14) ]. FOR MILITARY MEDICAL USE ONLY Pyridostigmine bromide is a cholinesterase inhibitor indicated for pretreatment against the lethal effects of soman nerve agent poisoning in adults. ( 1 ) Pyridostigmine bromide is for use in conjunction with Protective garments, including a gas mask, and Immediate atropine and pralidoxime therapy at the first sign of nerve agent poisoning. ( 1 )

Extended-Release Tablets: 105 mg, peach, oval, coated, unscored, biconvex tablets imprinted with “A2 463” on one side and plain on the other side. A hole may be visible on one side of the tablet. Extended-release tablets: 105 mg ( 3 )

Pyridostigmine bromide extended-release tablets are contraindicated in patients with: Mechanical intestinal or urinary obstruction Known hypersensitivity to pyridostigmine or other anticholinesterase agents Mechanical intestinal or urinary obstruction. ( 4 ) Known hypersensitivity to pyridostigmine or other anticholinesterase agents. ( 4 )

At the first sign of soman poisoning pyridostigmine must be stopped, and atropine and 2-PAM must be administered immediately. ( 5.1 ) Use with caution in persons with increased risk of anticholinergic reactions, such as persons with bronchial asthma, chronic obstructive pulmonary disease, bradycardia, cardiac arrhythmias, beta blocker treatment (increased risk of anticholinergic reactions). ( 5.2 ) Use with caution in persons with bromide sensitivity. ( 5.3 ) In case of serious adverse reactions, advise personnel to temporarily discontinue pyridostigmine and seek immediate medical attention. ( 5.4 )

5.1 Risk of Improper Use of Pyridostigmine Bromide Risk of Not Stopping Pyridostigmine Bromide and Using Atropine and Pralidoxime in the Event of Soman Exposure Pyridostigmine bromide is for use as pretreatment for exposure to soman nerve agent and must not be taken after exposure to soman nerve agent [see Dosage and Administration (2.1 , 2.2) ]. Pyridostigmine bromide pretreatment offers no benefit against the nerve agent soman unless the nerve agent antidotes, atropine and pralidoxime (2-PAM), are administered once symptoms of poisoning appear. Discontinue pyridostigmine at the first sign of nerve agent poisoning because it may exacerbate the effects of a sublethal exposure to soman if taken immediately before exposure (e.g., when the gas attack alarm is given) or at the same time as poisoning by soman [see Clinical Pharmacology (12.2) ]. Signs of nerve agent poisoning can include runny nose; watery eyes; small, pinpoint pupils; eye pain; blurred vision; drooling and excessive sweating; cough; chest tightness; rapid breathing; diarrhea; increased urination; confusion; drowsiness; weakness; headache; nausea, vomiting, and/or abdominal pain; slow or fast heart rate; and/or abnormally low or high blood pressure. Risk of Not Wearing Protective Garments Pyridostigmine bromide is not the primary protection against exposure to soman nerve agent. The primary protection against exposure to chemical nerve agents is the wearing of protective garments including masks, hoods, and overgarments designed specifically for this use. Individuals must not rely solely upon pretreatment with pyridostigmine bromide and on the antidotes, atropine and pralidoxime (2-PAM), to provide complete protection from poisoning by soman nerve agent.

5.2 Increased Risk of Anticholinergic Adverse Reactions in Individuals with Certain Conditions Pulmonary Conditions Drugs that increase cholinergic activity, including pyridostigmine bromide, should be used with caution in persons with bronchial asthma or chronic obstructive pulmonary disease. Cardiovascular Conditions Because pyridostigmine bromide increases cholinergic activity, it may have vagotonic effects on heart rate, which can lead to bradycardia or cardiac arrhythmias. Genitourinary Tract or Gastrointestinal Tract Obstruction Drugs that increase cholinergic agents, including pyridostigmine bromide, could cause symptoms in persons susceptible to genitourinary tract or gastrointestinal tract obstruction. Conditions Treated with Beta Adrenergic Receptor Blockers Pyridostigmine bromide should be used with caution in people being treated for hypertension or glaucoma with beta adrenergic receptor blockers [see Drug Interactions (7.2) ].

5.3 Use in Bromide-Sensitive Individuals Caution should be taken when administering pyridostigmine bromide to individuals with known bromide sensitivity. A skin rash may be observed in bromide-sensitive patients, which usually subsides upon discontinuance of the medication. The risks and benefits of administration must be weighed against the potential for rash or other adverse reactions in these individuals.

5.4 Serious Adverse Reactions, Such as Difficulty Breathing, Severe Dizziness, Loss of Consciousness Pyridostigmine bromide can cause serious adverse reactions such as difficulty breathing, severe dizziness, or loss of consciousness. If these adverse reactions occur, patients should temporarily discontinue use of pyridostigmine bromide and seek immediate medical attention. Personnel should report serious adverse events to their commander and responsible medical officer.

The following serious adverse reactions are discussed elsewhere in the labeling: Risk of Improper Use of Pyridostigmine Bromide [see Warnings and Precautions (5.1) ] Individuals at Increased Risk of Anticholinergic Adverse Reactions [see Warnings and Precautions (5.2) ] Use in Bromide-Sensitive Individuals [see Warnings and Precautions (5.3) ] Serious Adverse Reactions, Such as Difficulty Breathing, Severe Dizziness, Loss of Consciousness [see Warnings and Precautions (5.4) ] Most common adverse reactions ( ≥ 3% ) are diarrhea, abdominal pain, dysmenorrhea, and twitch. ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Amneal Pharmaceuticals at 1-877-835-5472 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 a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. The adverse reactions to pyridostigmine bromide are typically of two varieties: muscarinic and nicotinic. Muscarinic adverse reactions include abdominal cramps, bloating, flatulence, diarrhea, emesis, increased peristalsis, nausea, hypersalivation, urinary incontinence, increased bronchial secretion, diaphoresis, miosis, and lacrimation. Nicotinic adverse reactions are comprised chiefly of muscle cramps, fasciculations, and weakness. In a controlled study of 90 healthy volunteers comparing immediate-release pyridostigmine bromide 30 mg every 8 hours, which provides exposures comparable to pyridostigmine bromide 105 mg extended-release tablets once daily, to placebo for 21 days, the adverse reactions that were reported in 2% or more of subjects is included in Table 1. The most common adverse reactions (≥ 3%) are diarrhea, abdominal pain, dysmenorrhea, and twitch. Table 1: Incidence of Adverse Reactions ≥ 2% Adverse Reaction Pyridostigmine N = 60 % Placebo N = 30 % Diarrhea 7 0 Abdominal pain 7 0 Dysmenorrhea 5 0 Twitch 3 0 Myalgia 2 0 Dry skin 2 0 Urinary frequency 2 0 Epistaxis 2 0 Amblyopia 2 0 Hypesthesia 2 0 Neck pain 2 0 Other less common adverse reactions seen during controlled and uncontrolled clinical trials for pyridostigmine include the following: Pulmonary: Exacerbation of acute bronchitis and asthma Cardiovascular: Elevated blood pressure, decreased heart rate (4-6 beats per minute), chest tightness Eyes: Change in vision, eye pain Neurologic: Headache, hypertonia, difficulty in concentrating, confusion, disturbed sleep, tingling of extremities, numbness of the tongue Skin: Increased sweating, rash, alopecia Digestive: Vomiting, borborygmi, nausea, bloating, flatulence General: Warm sensation, lethargy/drowsiness, depressed mood During safety studies at the recommended dosage of immediate release pyridostigmine bromide 30 mg every 8 hours, which provides exposures comparable to pyridostigmine bromide 105 mg extended-release tablets once daily, there were two reports of loss of consciousness, one of which also included urinary and fecal incontinence, stiffness of the upper torso and arms, post-syncopal skin pallor, post-syncopal confusion, and post-syncopal weakness. Central Nervous System Adverse Reactions Pyridostigmine bromide is a quaternary ammonium compound and does not readily cross the blood-brain barrier. Compared to the peripheral effects of pyridostigmine bromide, central nervous system manifestations are less frequent and less serious, primarily consisting of headache and vertigo, with minor and clinically insignificant changes in heart rate, blood pressure, and respiratory function.

Mefloquine: Additive effect on gastrointestinal tract and atrial rate. ( 7.1 ) Anticholinesterase drugs for glaucoma treatment: Additive effect. ( 7.2 ) Narcotics: Exacerbation of bradycardia possible. ( 7.3 ) Depolarizing neuromuscular blocking agents: Increased effect. ( 7.4 ) Non-depolarizing neuromuscular blocking agents: Dose may need to be increased. ( 7.4 ) Aminoglycoside antibiotics, local and some general anesthetics, antiarrhythmic agents, and other drugs that interfere with neuromuscular transmission should be used cautiously, if at all. ( 7.4 ) Drugs converted to pantothenic acid (e.g., dexpanthenol): Additive effect. ( 7.5 )

7.1 Mefloquine Concomitant use of mefloquine and pyridostigmine bromide may have additive effects on the gastrointestinal tract, the most common of which is loose bowels. Additive effects on the atrial rate may also occur with concomitant use of mefloquine and pyridostigmine bromide.

7.2 Other Anticholinesterase Drugs Concomitant use of anticholinesterase drugs used in the treatment of glaucoma and pyridostigmine bromide may have an additive effect that may cause or exacerbate problems with night vision.

7.3 Narcotics The bradycardia associated with the use of narcotics may exacerbate pyridostigmine-induced bradycardia.

7.4 Drugs that Interfere with Neuromuscular Transmission Particular caution should be observed in the administration of depolarizing neuromuscular blocking agents (e.g., succinylcholine) during surgery since the degree of neuromuscular blockade that ensues may be enhanced by previously administered pyridostigmine bromide. Doses of non-depolarizing neuromuscular blocking agents (e.g., pancuronium bromide) may need to be increased in patients previously administered pyridostigmine bromide. Atropine antagonizes the muscarinic effects of pyridostigmine bromide, and this interaction is utilized to counteract the muscarinic symptoms of pyridostigmine bromide toxicity. Anticholinesterase agents are sometimes effective in reversing neuromuscular block induced by aminoglycoside antibiotics. However, aminoglycoside antibiotics, local and some general anesthetics, antiarrhythmic agents, and other drugs that interfere with neuromuscular transmission should be used cautiously, if at all, during treatment with pyridostigmine bromide.

7.5 Drugs Converted to Pantothenic Acid Concomitant use of drugs that are converted to pantothenic acid in vivo (e.g., dexpanthenol) and pyridostigmine bromide may have additive effects by increasing production of acetylcholine.

Renal impairment: Increased risk of side effects; careful dose selection. In persons with renal impairment, renal function monitoring may be useful. ( 8.6 )

8.1 Pregnancy Risk Summary Available data from case reports and case series over decades of use with pyridostigmine bromide have not identified a drug-associated risk of major birth defects, miscarriage, or other adverse maternal or fetal outcomes. Treatment with pyridostigmine bromide for soman nerve agent poisoning during pregnancy should not be delayed because exposure to soman during pregnancy may increase the risk of maternal and fetal morbidity and mortality. In animal studies, oral administration of pyridostigmine during organogenesis resulted in adverse developmental effects (increased embryofetal mortality and fetal structural abnormalities), at clinically relevant doses (see Data) . The background risk for major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. 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. Data Animal Data Oral administration of pyridostigmine to pregnant rats during organogenesis resulted in increases in embryofetal deaths and incidences of fetal skeletal variations at the highest dose tested (30 mg/kg/day), which was also maternally toxic. A slight increase in the incidence of hydronephrosis was observed at all dose levels (lowest dose tested was 3 mg/kg/day). A no-effect dose for adverse effects on embryofetal development in the rat was not identified. The lowest dose tested (3 mg/kg/day) is less than the recommended human dose (105 mg) on a body surface area (mg/m 2 ) basis. Oral administration of pyridostigmine to pregnant rabbits during organogenesis resulted in an increase in the incidence of visceral variations at the highest dose tested (45 mg/kg/day), which was also maternally toxic. An increased incidence of blood vessel variations was observed at all doses (lowest dose tested was 5 mg/kg/day). A no-effect dose for adverse effects on embryofetal development in the rabbit was not identified. The lowest dose tested (5 mg/kg/day) is less than the recommended human dose on a body surface area (mg/m2) basis.

8.2 Lactation Risk Summary Pyridostigmine bromide is present in human milk. Based on limited data, pyridostigmine bromide was not detected in the plasma of infants who were breastfed by mothers taking pyridostigmine bromide. There are no data on the effects on milk production. The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for pyridostigmine bromide and any potential adverse effects on the breastfed infant from pyridostigmine bromide or from the underlying maternal condition.

8.4 Pediatric Use Safety and effectiveness in pediatric patients have not been established.

8.5 Geriatric Use Clinical studies of pyridostigmine bromide did not contain sufficient numbers of subjects aged 65 and over to determine whether they respond differently than younger subjects. In general, dose selection for an elderly patient should be cautious, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy. This drug is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function [see Clinical Pharmacology (12.3) ], care should be taken in dose selection, and it may be useful to monitor renal function.

8.6 Renal Impairment This drug is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Caution should be observed, and dosage be selected carefully, when administering pyridostigmine bromide to patients with impaired renal function. [see Clinical Pharmacology (12.3) ] . It may be useful to monitor renal function.

Pyridostigmine is a reversible cholinesterase inhibitor.