amifampridine phosphate: clinical use

Prescribing considerations

• Initiate under a physician experienced in managing Lambert-Eaton myasthenic syndrome.
• Assess renal and hepatic function because impairment can increase exposure and adverse effects.
• Review medicines for QT prolongation, narrow therapeutic windows, seizure-threshold effects and neuromuscular-blocking activity.
• Use caution with previous schwannoma, neurofibromatosis type 2 or schwannomatosis.

Contraindications and cautions

• Hypersensitivity to the active substance or excipients
• Epilepsy
• Uncontrolled asthma
• Congenital QT syndromes
• Concomitant sultopride, QT-prolonging medicines or medicines with a narrow therapeutic window

Monitoring

• Clinical assessment and ECG at treatment initiation and periodically thereafter
• Immediate ECG if symptoms suggest an arrhythmia
• Close adverse-effect monitoring in renal or hepatic impairment
• Review treatment if a painful mass or symptoms of compressive neuropathy suggest schwannoma
• Stop treatment if a seizure occurs

Clinical pharmacology

Amifampridine blocks presynaptic voltage-dependent potassium channels, prolonging depolarisation and increasing calcium-dependent acetylcholine release. It is mainly metabolised by N-acetyltransferase to a 3-N-acetyl metabolite; NAT2 phenotype substantially affects exposure, and elimination is predominantly urinary.

Formulation and product differences

• The selected product contains amifampridine as its phosphate salt, expressed as equivalent amifampridine.
• The white, round oral tablet is scored and can be divided into equal halves.
• Store in the original package, protected from light and moisture.

Tablet

Route: Oral

Strengths: 10 mg