From the FDA Drug Label
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. 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 management for Lambert-Eaton syndrome is treatment with FIRDAPSE (amifampridine), a potassium channel blocker. The dosage should be started at 15 mg to 30 mg daily, in divided doses, and can be increased by 5 mg daily every 3 to 4 days, with a maximum single dose of 20 mg and a maximum daily dose of 100 mg 1.
- Key considerations:
- Patients should be advised to take FIRDAPSE exactly as prescribed.
- Patients should be informed of the risk of seizures and hypersensitivity reactions.
- Patients should be instructed to notify their healthcare provider prior to starting any new medication.
- Patients who are pregnant or plan to become pregnant should inform their healthcare provider 1.
- Important safety information:
- FIRDAPSE can cause seizures and hypersensitivity reactions.
- FIRDAPSE is contraindicated in patients with a history of seizures or hypersensitivity to amifampridine or another aminopyridine 1.
From the Research
The recommended management for Lambert-Eaton myasthenic syndrome (LEMS) is to use amifampridine (3,4-diaminopyridine) as the first-line treatment, at a dose of 80 mg per day, divided into 3 or 4 times a day, as it has been shown to be the most effective drug for symptomatic treatment in LEMS, with minimal side effects, as reported in the most recent and highest quality study 2.
Key Considerations
- Amifampridine works by increasing the release of acetylcholine at the presynaptic membrane, thereby improving muscle strength and reducing symptoms of LEMS.
- The recommended dose of 80 mg per day is supported by studies that have shown its efficacy and safety in treating LEMS, with the most common side effects being mild and including paresthesia 3.
- It is essential to note that approximately 50% of LEMS patients have associated small cell lung cancer, and thorough cancer screening is crucial, particularly in patients over 50 with a smoking history.
Additional Treatment Options
- For patients with inadequate response to amifampridine, pyridostigmine may be added to inhibit acetylcholine breakdown, although its use is not as well-supported by recent evidence.
- Immunosuppressive therapy, such as prednisone and azathioprine, may be necessary in some cases, but its use should be carefully considered due to potential side effects.
- Intravenous immunoglobulin or plasmapheresis may provide temporary improvement in severe or refractory cases, but their use is not as well-established as amifampridine.
Important Precautions
- Patients with LEMS should avoid medications that may worsen neuromuscular transmission, including certain antibiotics, beta-blockers, calcium channel blockers, and magnesium.
- Regular follow-up is crucial to monitor treatment efficacy and adjust medications as needed, with attention to potential side effects of immunosuppressive therapy.