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Amifampridine
Amifampridine primarily improves muscle functioning by increasing acetylcholine in the neuromuscular junction.[1][2] Common brand names are Firdapse or Ruzurgi[3].
Theory
Amifampridine, also known as 3,4-diaminopyridine or 3,4-DAP, belongs to the group of aminopyridines and is used in conditions where acetylcholine release is reduced, e.g., for treating Lambert-Eaton Myasthenic Syndrome (LEMS). It belongs to the category of potassium channel blockers and is closely related to fampridine, a drug used in multiple sclerosis to improve cognitive functioning and cognitive fatigue.[1] Another drug seeking to increase the amount of acetylcholine in the neuromuscular junction, but using another mechanism, is pyridostigmine.
Mechanism
Peripheral Effects
Amifampridine blocks the voltage-gated potassium channels and thus, potassium release. Thus, the nerve terminal remains in a depolarized state for a longer period of time which allows a longer opening of calcium channels releasing calcium ions into the presynaptic terminal. In turn, this triggers an increased release of neurotransmitters into the synaptic cleft, such as acetylcholine, which causes a muscle to contract. Thereby, more acetylcholine activates muscle receptors more strongly, and improves muscle function.[1]
Brainstem
Theoretically, amifampridine can also act in the brainstem. The presynaptic potassium channels affected in the peripheral nervous system also exist in the neurons of the central nervous system, including the brainstem which, among others, controls respiration, cardiovascular function, and alertness, and blockage of potassium channels can increase neurotransmitter release there as well. Based on animal studies, potassium channel blockers may alter neuronal excitability or reflexes. Regarding its use in LEMS, this is clinically irrelevant except for side effects which can be minimized by adequate dosage.[2]
Evidence
In a case report on five patients, amifampridine reduced fatigue and excessive sleep duration while improving cognitive functioning in post-COVID syndrome. Illness duration prior to treatment ranged from 4 to 14 months. Overall, a significant increase in Bell score was observed and confirmed by a double blinded discontinuation trial in two patients. [1]
Risks and safety
Amifampridine is a potent convulsant with a narrow therapeutic window[4]. Therefore, it should not be used in patients with a history of seizures and with care, if liver or kidney problems are present[3].
See also
Learn more
WebMD: https://www.webmd.com/drugs/firdapse-amifampridine
Wikipedia: https://en.wikipedia.org/wiki/Amifampridine
References
- ↑ 1.0 1.1 1.2 1.3 Boehmeke, Thomas (2024). "Reduced Fatigue Symptoms in the Post-COVID Syndrome With Amifampridine: A Collective Casuistry With Double-Blind Discontinuation Trials" (PDF). Cureus. 16 (1).
- ↑ 2.0 2.1 Strupp, T; Teufel, J; Zwergal, A; Schniepp, R (2017). "Aminopyridines for the treatment of neurologic disorders". Neurol Clin Pract. 7 (1).
- ↑ 3.0 3.1 "Firdapse (amifampridine): Uses, Side Effects, Interactions, Pictures, Warnings & Dosing - WebMD". www.webmd.com. Retrieved June 30, 2026.
- ↑ Judge, Susan I.V.; Bever Jr., Christopher T. (Jul, 2006). "Potassium channel blockers in multiple sclerosis: Neuronal Kv channels and effects of symptomatic treatment". Pharmacology & Therapeutics. 111 (1): 224–259. doi:10.1016/j.pharmthera.2005.10.006. Retrieved Jul 01, 2026. Check date values in:
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