Preliminary trial of 3,4-diaminopyridine in patients with multiple sclerosis.

Ten patients with multiple sclerosis (MS) were enrolled in a preliminary trial of the potassium channel blocker, 3,4-diaminopyridine, to evaluate drug toxicity and pharmacokinetics. The patients were treated with oral 3,4-diaminopyridine, first with increasing single doses up to 100 mg and then with divided dosage for up to 3 weeks. Paresthesias were reported by all patients and abdominal pain was dose limiting in 6 patients. 3,4-Diaminopyridine levels and half-life varied widely from patient to patient. Cerebrospinal fluid levels of 3,4-diaminopyridine were about 10% of those in serum. Neither seizures nor epileptiform changes on electroencephalographic examination occurred. Small reversible improvements in specific neurological deficits were seen on examination in all patients and reversible improvement in visual evoked response latencies were found in 2 patients. These results suggest that further study of 3,4-diaminopyridine in patients with MS is warranted.