AMBENONIUM CHLORIDE

AMBENONIUM CHLORIDE
(am-be-noe'nee-um)
Mytelase
Classifications: cholinesterase inhibitor;
Therapeutic: cholinesterase inhibitor

Prototype: Neostigmine
Pregnancy Category: C

Availability

10 mg tablets

Action

Inhibits destruction of acetylcholine (ACh) by cholinesterase, thereby prolonging effects of ACh (neurotransmitter) at postsynaptic receptor sites. Has direct stimulant effect on striated muscles.

Therapeutic Effect

Improves muscular strength in myasthenia gravis.

Uses

Symptomatic treatment of myasthenia gravis for patients who cannot tolerate neostigmine bromide or pyridostigmine bromide because of bromide sensitivity. Has been used in conjunction with corticosteroids, ephedrine sulfate, and potassium chloride to increase muscle strength.

Contraindications

Intestinal or urinary tract obstruction; patients receiving mecamylamine; pregnancy (category C); lactation.

Cautious Use

Epilepsy, bradycardia, cardiac arrhythmias, recent coronary occlusion; bronchial asthma; hyperthyroidism; older adults; vagotonia; peptic ulcer, megacolon.

Route & Dosage

Myasthenia Gravis
Adult: PO 2.5–5 mg t.i.d. or q.i.d., may increase q1–2d to 50–75 mg t.i.d. or q.i.d. if necessary
Child: PO 0.3 mg/kg/d in 3–4 divided doses, may need up to 1.5 mg/kg/d in 3–4 divided doses

Administration

Oral
  • Give with food or milk to minimize adverse effects.
  • Schedule larger doses when patient experiences the most fatigue or muscle weakness; to improve ability to eat, give drug 30–45 min before meals.
  • Store at 15°–30° C (59°–86° F) unless otherwise directed.

Adverse Effects (≥1%)

CNS: Exaggerated cholinergic (muscarinic) effects; muscle cramps, headache, confusion, dizziness, incoordination, fasciculations, agitation, restlessness, muscle weakness, paralysis, slurred speech, convulsions, respiratory depression. CV: Bradycardia. GI: Nausea, vomiting, diarrhea, abdominal cramps, excessive salivation. Special Senses: Blurred vision, lacrimation. Respiratory: Bronchospasm, increased bronchial secretions, dyspnea. Other: Diaphoresis.

Interactions

Drug: Demecarium and other cholinesterase inhibitors possibly compound toxicity; mecamylamine, succinylcholine, procainamide, quinidine, aminoglycosides increase neuromuscular blocking effects with possibility of respiratory depression; atropine antagonizes effects of ambenonium.

Pharmacokinetics

Absorption: Poorly absorbed from GI tract. Onset: 20–30 min. Duration: 3–8 h.

Nursing Implications

Assessment & Drug Effects

  • Therapeutic effect may not be apparent for several days after initiation of therapy.
  • Keep atropine sulfate immediately available to treat severe cholinergic reactions.
  • Monitor for S&S of overdosage (muscle weakness within 1 h; headache, weakness of muscles of neck, chewing, and swallowing, increased salivation) and inadequate ventilation (unusual apprehension, restlessness, rapid pulse and respirations, rising BP).
  • Monitor vital signs during dosage adjustment periods.
  • Note: Muscle weakness beginning 3 h or more after drug administration is probably due to underdosage or drug resistance.

Patient & Family Education

  • Follow directions for taking this drug (see ADMINISTRATION).
  • Learn to recognize adverse effects, how to modify the doses accordingly, and when to take atropine.
  • Note: During long-term therapy the drug may become ineffective; responsiveness usually returns when dosage is reduced or drug is withdrawn for several days.
  • Carry medical identification indicating medical diagnosis and medication(s) being taken.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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