Amifampridine Phosphate (446254-47-3)

Amifampridine Phosphate Chemical Structure

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What is Amifampridine phosphate?

Amifampridine is a 4-Aminopyridine derivative used as a drug, predominantly in the treatment of a number of rare muscle diseases. The drug formulation amifampridine phosphate contains the phosphate salt, more specifically 4-aminopyridine-3-ylammonium dihydrogen phosphate. This salt is soluble in water and forms prismatic, monoclinic crystals (space group C2/c). It is stable and doesn’t need to be refrigerated.

The product is currently under development. Samples are available from R&D.
Name of Product Amifampridine phosphate
IUPAC Name phosphoric acid;pyridine-3,4-diamine
Synonyms 3,4-Diaminopyridine phosphate; 3,4-Pyridinediamine, phosphate (1:1); Firdapse (TN)
CAS No 446254-47-3
Molecular Formula C5H10N3O4P
Molecular Weight 207.12 g/mol
Pubchem CID 9920716
Pubchem SID 463798108


Amifampridine Phosphate is used to treat a rare auto-immune disorder of the neuromuscular junction that affects nerves and muscles, i.e., Lambert-Eaton myasthenic syndrome (LEMS). This disorder causes your body’s immune system to attack healthy nerve cells, which results in muscle weakness. Firdapse (amifampridine) was formally approved by the US FDA for the treatment of adults with LEMS as recently as November 2018. It is also used in the treatment of other congenital myasthenic syndromes due to its K-channel blocking properties.

Mechanism of Action: Acetylcholine release is suppressed in Lambert–Eaton myasthenic syndrome because antibodies implicated in the host response to certain malignancies cross-react with Ca2+ channels on the prejunctional membrane. Amifampridine works by increasing action potential duration by blocking potassium channel efflux in nerve terminals. Ca2+ channels can thus remain open for longer periods of time, allowing for increased acetylcholine release to stimulate muscle near the endplate.

Dosage: It is presently utilised as the first-line symptomatic treatment for LEMS in adult patients, and it is best administered as oral tablets in divided doses three or four times per day.

Side effects

Tingling may occur around the mouth, tongue, face, fingers, toes, and other body regions. Cold symptoms (such as a stuffy/runny nose, cough, sore throat, fever, sneezing), nausea, diarrhoea, constipation, headache, stomach/back pain, muscle spasms, or dizziness are all possible. Inform your doctor or pharmacist immediately if any of these side effects persist or worsen.

Get medical help right away if you notice any very serious side effects, including seizures, symptoms of liver damage, or vision changes.


Q. What class of drug is Amifampridine?

Amifampridine is a voltage-gated potassium channel blocker used to treat Lambert-Eaton myasthenic syndrome.

Q. What is the difference between Firdapse and Ruzurgi?
Firdapse is a potassium channel blocker manufactured by Catalyst Pharmaceuticals, Inc. and used to treat adults with Lambert-Eaton myasthenic syndrome (LEMS). Ruzurgi is also a potassium channel blocker manufactured by Jacobus Pharmaceutical Company Inc. but is used to treat Labert-Eaton myasthenic syndrome (LEMS) in patients aged 6 to 17 years.
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