Firdapse® – The Only Treatment for Adults with Lambert-Eaton Myasthenic Syndrome

Drug Review: Volume 22, Issue 5

Lambert-Eaton Myasthenic Syndrome (LEMS) is a rare autoimmune disorder that disrupts the connection between nerves and muscles resulting in the gradual onset of muscle weakness, which begins in the legs and hips and radiates to the arms, hands, and facial area. Other symptoms include fatigue, muscle aches, absent or diminished reflexes, constipation, dry mouth, and erectile dysfunction. These symptoms worsen over time, and ultimately result in functional impairment and reduced quality of life. LEMS currently affects approximately 340 Canadians. In approximately 50 to 60% of cases, LEMS may be related to cancer, most of which are small cell lung cancer (SCLC). In such cases, symptoms can develop more quickly compared to those who do not present with cancer.


While there is no cure for LEMS, current treatment involves improving symptoms and identifying and treating underlying diseases such as SCLC. Traditionally for symptom relief, it may involve the use of off-label medications to increase muscle contraction, such as amifampridine, pyridostigmine, and immunologic/ immunosuppressive agents (e.g., prednisone, azathioprine). While amifampridine has been used for the treatment of LEMS for several decades, it did not obtain Health Canada approval until recently with the approval of Firdapse^® (amifampridine). Pyridostigmine provides only minimal benefit in treatment of symptoms, and immunologic/immunosuppressive agents while effective, can lead to increased tumor growth in cancer-associated cases of LEMS and are therefore recommended to only patients not sufficiently responsive to pyridostigmine or amifampridine.


Firdapse^® is the only agent approved by Health Canada for the treatment of LEMS symptoms. Firdapse^® is administered orally and dosed three to four times a day. The recommended daily dose is 15 to 30 mg; however, some patients benefit from a dosage of up to 80 mg daily. Firdapse^® is a well tolerated medication that reduces worsening of muscle weakness; however, can cause paresthesia (tingling, burning, pricking or numbness of the skin), abdominal pain, nausea, and diarrhea.


Firdapse^® reduced its cost by approximately 75% from the original price to improve affordability, rendering the current annual maximum cost to be $63,948. ClaimSecure has further partnered with the manufacturer to improve Firdapse^®’s cost-effectiveness. As a safe and effective treatment option for LEMS, Firdapse^® is covered under Special Authorization for ClaimSecure groups subscribed to Managed Formularies.