4-aminopyridine (also known as 4-AP and Fampridine) is a drug that blocks the potassium channels in neurons. This effectively improves the transmission of nerve impulses down damaged axons. It does not replace damaged myelin but users of 4-aminopyridine report dramatic improvement in a number of symptoms especially paraesthesia. It should be born in mind that this is an experimental drug and the side-effects are uncertain. Dosages should be carefully regulated as potassium is a chemical that is used extensively in other parts of the body including heart functions.
Agriculturally, 4-AP is used as an extremely effective bird poison sold under the brand name Avitrol. It is highly toxic to all mammals including humans if dosages are exceeded, and, as an experimental drug, recommended dose data is unavailable.
A slow release formulation of 4-aminopyridine is supplied by the Irish drug company, Elan Corporation, and is currently being tested by Acorda in two phase II trials in the US. It is currently awaiting authorisation by the US Federal Drug Agency (FDA).
Wheelweb - Aminopyridine Drug
Extoxnet PIP - 4-aminopyridine