4ap

4-aminopyridine (4-AP) is a small heterocyclic amine and a derivative of pyridine. It is best known in a pharmacological context as a potent blocker of voltage-gated potassium channels, particularly those of the Kv family, and it is used in both research and medicine. In neuroscience, 4-AP is employed as a tool to study neuronal excitability and synaptic transmission because it alters action potential dynamics.

The primary mechanism by which 4-AP exerts clinical effects is by blocking potassium efflux during and after an action potential. This prolongs the duration of action potentials, increases calcium influx, and enhances neurotransmitter release at synapses. In demyelinated nerve fibers, such as those affected in multiple sclerosis, this can improve the propagation of nerve signals that would otherwise fail or be slowed, translating to functional benefits in motor performance.

In medical use, 4-aminopyridine is marketed in the pharmaceutical form dalfampridine (brand name Ampyra in some regions) for improving walking in adults with multiple sclerosis. It is available as an extended-release tablet, commonly prescribed as 10 mg twice daily. Treatment requires consideration of renal function, as reduced kidney function can raise drug exposure and seizure risk. The most serious safety concern is the potential for seizures, especially at high doses or in patients with predisposing factors. Other common adverse effects include headache, dizziness, and urinary tract infections. It is not a cure for MS and is not approved for other conditions with established efficacy.

Beyond its clinical use, 4-AP remains a widely used pharmacological tool in neuroscience research to study ion channel function and neuronal excitability. Its therapeutic application continues to be evaluated, with attention to safety profiles and patient selection.