pyridostigmine bromide - definition of pyridostigmine bromide in the Medical dictionary - by the Free Online Medical Dictionary, Thesaurus and Encyclopedia.

Pyridostigmine bromide (Mestinon)

An anticholinesterase drug used in treating myasthenia gravis.

pyridostigmine bromide

[pir′idōstig′mēn]

an acetylcholinesterase inhibitor that prolongs the effects of neuronally released acetylcholine.

indications It is prescribed in the treatment of myasthenia gravis and is used as an antagonist to nondepolarizing muscle relaxants, such as curare.

contraindications Intestinal or urinary obstruction, bradycardia, hypotension, or known hypersensitivity to this drug or to other anticholinesterases prohibits its use.

adverse effects Among the more serious adverse effects are nausea, diarrhea, abdominal cramps, muscle cramps, and weakness.

pyridostigmine bromide, (pir´

dōstig´mēn),

n brand names: Mestinon, Regonol;
drug class: cholinergic;
action: inhibits destruction of acetylcholine, which increases concentration at sites where acetylcholine is released. This facilitates transmission of impulses across myoneural junction;
uses: nondepolarizing muscle relaxant antagonist, myasthenia gravis.

pyridostigmine bromide

Mestinon, Mestinon-SR (CA), Mestinon Timespan, Regonol

Pharmacologic class: Anticholinesterase

Therapeutic class: Muscle stimulant, antimyasthenic

Pregnancy risk category C

Action

Prevents acetylcholine destruction, resulting in stronger contractions of muscles weakened by myasthenia gravis or curare-like neuromuscular blockers

Availability

Injection: 5 mg/ml

Syrup: 60 mg/5 ml

Tablets: 60 mg

Tablets (extended-release): 180 mg

⊘Indications and dosages

➣ Myasthenia gravis

Adults: 600 mg P.O. given over 24 hours, with doses spaced for maximum symptom relief. For myasthenic crisis, 2 mg or 1/30 of oral dose I.M. or very slow I.V. q 2 to 3 hours.

➣ Postoperative reversal of nondepolarizing neuromuscular blockers

Adults: 10 to 20 mg slow I.V. injection (range is 0.1 to 0.25 mg/kg) with or immediately after 0.6 to 1.2 mg atropine sulfate I.V.

Dosage adjustment

• Renal impairment
• Seizure disorders

Off-label uses

• Myasthenia gravis in children
• Constipation in patients with Parkinson's disease
• Nerve agent prophylaxis

Contraindications

• Hypersensitivity to drug or bromides
• Mechanical intestinal or urinary tract obstruction

Precautions

Use cautiously in:
• seizure disorders, bronchial asthma, coronary occlusion, arrhythmias, bradycardia, hyperthyroidism, peptic ulcer, vagotonia, cholinergic crisis
• pregnant or breastfeeding patients
• children (safety and efficacy not established).

Administration

☞ Don't exceed I.V. injection rate of 1 mg/minute.
☞ Don't give concurrently with other anticholinesterase drugs.
• Have atropine available for use in emergencies.

Route	Onset	Peak	Duration
P.O.	20-30 min	Unknown	Unknown
P.O. (extended)	30-60 min	Unknown	6-12 hr
I.V.	2-5 min	Unknown	2-4 hr
I.M.	<15 min	Unknown	2-4 hr

Adverse reactions

CNS: headache, dysarthria, dysphoria, drowsiness, dizziness, headache, syncope, loss of consciousness, seizures

CV: decreased cardiac output leading to hypotension, bradycardia, nodal rhythm, atrioventricular block, cardiac arrest, arrhythmias

EENT: diplopia, lacrimation, miosis, spasm of accommodation, conjunctival hyperemia

GI: nausea, vomiting, diarrhea, abdominal cramps, increased peristalsis, flatulence dysphagia, increased salivation

GU: urinary frequency, urgency, or incontinence

Musculoskeletal: muscle weakness, fasciculations, and cramps; joint pain

Respiratory: increased pharyngeal and tracheobronchial secretions, dyspnea, central respiratory paralysis, respiratory muscle paralysis, laryngospasm, bronchospasm, bronchiolar constriction

Skin: diaphoresis, flushing, rash, urticaria

Other: thrombophlebitis at I.V. site, cholinergic crisis, anaphylaxis

Interactions

Drug-drug. Aminoglycosides: potentiation of neuromuscular blockade

Anesthetics (general and local), antiarrhythmics: decreased anticholinesterase effects

Atropine, belladonna derivatives: suppression of parasympathomimetic GI symptoms (leaving only fasciculations and voluntary muscle paralysis as signs of anticholinesterase overdose)

Corticosteroids: decreased anticholinesterase effects; after corticosteroid withdrawal, increased anticholinesterase effects

Ganglionic blockers (such as mecamylamine): increased anticholinesterase effects

Magnesium: antagonism of beneficial anticholinesterase effects

Nondepolarizing neuromuscular blockers (atropine, pancuronium, tubocurarine): antagonism of neuromuscular blockade and reversal of muscle relaxation after surgery (with parenteral pyridostigmine)

Other anticholinesterase drugs: in patients with myasthenia gravis, symptoms of anticholinesterase overdose that mimic underdose, causing patient's condition to worsen

Succinylcholine: increased and prolonged neuromuscular blockade (including respiratory depression)

Patient monitoring

• Assess patient's response to each dose.
• Monitor vital signs, ECG, and cardiovascular and respiratory status.
☞ Assess for signs and symptoms of overdose, which indicate cholinergic crisis.

Patient teaching

• If patient is using syrup, advise him to pour it over ice.
• Instruct patient using extended-release tablets not to crush them.
☞ Teach patient to recognize and promptly report signs and symptoms of overdose, including muscle fasciculations, sweating, excessive salivation, and constricted pupils.
• Tell patient drug may cause headache and muscle cramps. Encourage him to discuss activity recommendations and pain management with prescriber.
• Advise patient to monitor and report his response to ongoing therapy so that optimal dosage can be determined.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs mentioned above.