FDA approves increased amifampridine maximum daily dose to treat Lambert-Eaton myasthenic syndrome


The maximum daily dose has increased from 80 mg to 100 mg.

FDA approves increased amifampridine maximum daily dose to treat Lambert-Eaton myasthenic syndrome | Image Credit: © Calin - © Calin - stock.adobe.com.

FDA approves increased amifampridine maximum daily dose to treat Lambert-Eaton myasthenic syndrome | Image Credit: © Calin - © Calin - stock.adobe.com.

The FDA approved Catalyst Pharmaceuticals' supplemental New Drug Application (sNDA) for an increased daily dose of amifampridine (Firdapse) for both adults and pediatric patients with Lambert-Eaton myasthenic syndrome (LEMS).1

With the federal agency's decision, the maximum daily dose increased from 80 mg to 100 mg, for adults and pediatric patients who weigh more than 45 kg, allowing for greater flexibility in treatment regimens for the management of LEMS. The approval increases dosing options for the only currently-approved treatment for LEMS in the United States, according to a press release from Catalyst Pharmaceuticals.1

LEMS, a rare autoimmune disorder characterized by muscle weakness and fatigue, sees the immune system attack the body's tissues. Attacks occur at the connection between nerve and muscle, interfering with the nerve's ability to send signals to muscle cells.2

"This pivotal achievement further underscores our dedication to meeting the evolving needs of LEMS patients and their healthcare providers," said Richard J. Daly, president, CEO, Catalyst, in a statement. "We believe that this milestone will have a meaningful impact on the lives of LEMS patients, offering a new level of flexibility in treatment while aligning with our overarching mission to optimize LEMS patient outcomes.”1

Amifampridine is indicated to treat LEMS in adult and pediatric patients aged 6 years to 17 years. The potassium channel blocker works by increasing the release of acetylcholine at the neuromuscular junction, helping improve muscle function.1

According to the Cleveland Clinic, muscle weakness associated with LEMS typically begins in the upper legs, though other muscle groups in the arms can be impacted. In addition, these weaknesses can affect muscles involved in breathing, swallowing, and speech.3

Approximately 60% of LEMS cases occur in individuals who have an underlying malignancy, with small-cell lung cancer being the most common.3

Overall, common symptoms associated with LEMS include4:

  • Weak muscles
  • Trouble walking
  • Tingling sensations
  • Fatigue
  • Dry mouth
  • Trouble speaking and swallowing
  • Trouble breathing
  • Bladder and bowel changes
  • Erectile dysfunction


1. Catalyst Pharmaceuticals receives US FDA approval for increased maximum daily dose for Firdapse. Catalyst Pharmaceuticals. Press release. May 30, 2024. Accessed June 3, 2024. https://ir.catalystpharma.com/news-releases/news-release-details/catalyst-pharmaceuticals-receives-us-fda-approval-increased

2. Lambert-Eaton Myasthenic Syndrome (LEMS). Muscular Dystrophy Association. Accessed June 3, 2024. https://www.mda.org/disease/lambert-eaton-myasthenic-syndrome

3. Overview: What is Lambert-Eaton myasthenic syndrome (LEMS)? Cleveland Clinic. Updated May 21, 2022. Accessed June 3, 2024. https://my.clevelandclinic.org/health/diseases/23202-lambert-eaton-myasthenic-syndrome-lems

4. Lambert-Eaton Syndrome. Johns Hopkins Medicine. Accessed June 3, 2024. https://www.hopkinsmedicine.org/health/conditions-and-diseases/lamberteaton-syndrome

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