Amifampridine

What it is and how it works

Mechanism of Action The mechanism by which amifampridine exerts its therapeutic effect in LEMS patients has not been fully elucidated. Amifampridine is a broad-spectrum potassium channel blocker.

Indications

® is indicated for the treatment of Lambert-Eaton myasthenic syndrome (LEMS) in adults and pediatric patients 6 years of age and older. FIRDAPSE is a potassium channel blocker indicated for the treatment of Lambert-Eaton myasthenic syndrome (LEMS) in adults and pediatric patients 6 years of age and older.

Dosage and administration (summary)

Administer orally in divided doses (3 to 5 times daily). The recommended starting dosage for adults (any weight) and pediatric patients weighing 45 kg or more is 15 mg to 30 mg daily, in divided doses. Dosage can be increased by 5 mg daily every 3 to 4 days. The maximum single dose is 20 mg. Dosage is not to exceed a maximum of 100 mg daily. The recommended starting dosage for pediatric patients weighing less than 45 kg is 5 mg to 15 mg daily, in divided doses. Dosage can be increased by 2.5 mg daily every 3 to 4 days. The maximum single dose is 10 mg. Dosage is not to exceed a maximum of 50 mg daily.

Contraindications

is contraindicated in patients with: A history of seizures Hypersensitivity to amifampridine phosphate or another aminopyridine FIRDAPSE is contraindicated in patients with: A history of seizures Hypersensitivity to amifampridine or another aminopyridine

Warnings and precautions

Seizures: FIRDAPSE can cause seizures. Consider discontinuation or dose-reduction of FIRDAPSE in patients who have a seizure while on treatment. Hypersensitivity reactions: If a hypersensitivity reaction such as anaphylaxis occurs, FIRDAPSE should be discontinued and appropriate therapy initiated. Seizures FIRDAPSE can cause seizures. Seizures have been observed in patients without a history of seizures taking FIRDAPSE at the recommended doses, at various times after initiation of treatment, at an incidence of approximately 2%.

Pregnancy

Pregnancy Pregnancy Exposure Registry There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to FIRDAPSE during pregnancy. Physicians are encouraged to enroll pregnant patients, or pregnant women may register themselves in the registry by calling 855- 212-5856 (toll-free), using the Fax number 877-867-1874 (toll-fr…

Storage and supply

Storage and Handling Store FIRDAPSE tablets at 20°C to 25°C (68°F to 77°F) with excursions permitted from 15°C to 30°C (59°F to 86°F) . See Dosage and Administration for storage instructions for FIRDAPSE prepared suspension.

Source: Amifampridine Phosphate (Firdapse) — US FDA prescribing information, 2026-04-16, DailyMed. Summarised and shortened; the full label governs. Iranian registration, indications and labelling may differ.