Amifampridine (Dosage)

Amifampridine is a potassium channel inhibitor drug used in the treatment of myasthenic syndromes such as Lambert-Eaton syndrome. Polymorphisms in the NAT2 gene can determine the plasma concentrations of the drug and its genotyping can be useful for the adjustment of the appropriate dose.

Amifampridine is a drug that acts on the nervous system for the symptomatic treatment of Lambert-Eaton myasthenic syndrome.

MECHANISM OF ACTION

Amifampridine blocks voltage-dependent potassium channels by prolonging the depolarization of the presynaptic cell membrane, thus promoting calcium entry into the nerve ending. The resulting increase in intracellular calcium concentrations facilitates exocytosis of acetylcholine-containing vesicles, which in turn increases neuromuscular transmission. The result is an increase in muscle strength and resting compound muscle action potential amplitudes.

CONTRAINDICATIONS

Hypersensitivity to amifampridine; epileptic patients; patients with uncontrolled asthma; patients with congenital cardiac QT interval syndromes.

Amifampridine is contraindicated in concomitance with sultopride, with drugs that can prolong QTc and with drugs with narrow therapeutic margin.

Do not use during pregnancy. Not for use during lactation since it is not known whether amifampridine is excreted in human breast milk.

PRECAUTIONS

Extreme caution should be exercised when amifampridine is prescribed in patients with hepatic or renal insufficiency. Caution in patients at risk of epileptic seizures: if a seizure occurs immediately discontinue treatment with amifampridine. A clinical and electrocardiographic control should always be performed at the beginning of treatment and once a year thereafter. Amifampridine is not indicated to treat children under 18 years of age since there are no safety and efficacy data.

SIDE EFFECTS

Peripheral and peribuccal paresthesias; epigastralgia, diarrhea, nausea, abdominal pain; sleep disorders; convulsions, anxiety, dizziness, weakness, tiredness, headache, chorea, myoclonus; blurred vision; heart rhythm disturbances, palpitations; Raynaud's syndrome, cold extremities; cough, bronchial hypersecretion, asthma attacks in asthmatics or with a history of asthma; elevation of transaminases.

PHARMACOLOGICAL INTERACTIONS

Amifampridine increases the risk of seizures with: antidepressants (tricyclics, selective serotonin reuptake inhibitors), neuroleptics (phenothiazines and butyrophenones), mefloquine, bupropion, tramadol.

Amifampridine increases the effect of direct or indirect cholinesterase inhibitors, and decreases the effect of both inhibitors if amifampridine is taken concomitantly with: mivacurium, pipercurium, suxamethonium. Extreme precautions should be taken when administered concomitantly with drugs that are eliminated by metabolism or active secretion.

BRAND NAMES

  • Firdapse®
  • Rusurgui®

Genes analyzed

NAT2
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