FIRDAPSE improves neuromuscular function in LEMS by blocking potassium channels, supported by randomized trials demonstrating efficacy.

Mechanism and Clinical Efficacy in Lambert-Eaton Myasthenic Syndrome

FIRDAPSE (amifampridine) is a voltage-gated potassium channel blocker indicated for adult LEMS. Its mechanism enhances presynaptic acetylcholine release, improving neuromuscular transmission. Two randomized, double-blind studies (NCT01377922, NCT02970162) demonstrated efficacy: discontinuation led to significant worsening in Quantitative Myasthenia Gravis (QMG) scores (muscle weakness) and Subject Global Impression (SGI) scores (patient-reported well-being) versus continued therapy. Clinician-rated CGI-I scores also favored FIRDAPSE. Efficacy was observed in autoimmune and paraneoplastic LEMS subtypes. Therapeutic effects are dose-dependent, with optimal dosing individualized to balance symptom control and tolerability. Long-term durability beyond 18 months is not specified in the description.