Treatment of Lambert-Eaton syndrome: 3,4-diaminopyridine and pyridostigmine.

We used a new drug, 3,4-diaminopyridine, to treat five patients with the Lambert-Eaton syndrome, one with a carcinoma and four cryptogenic. The effects of intravenous, oral, and rectal administration were evaluated clinically and electrophysiologically after single doses and during continuous treatment for up to 21 months. 3,4-Diaminopyridine effectively ameliorated the neuromuscular and autonomic nervous system disorders without severe side effects. Anticholinesterase drugs strongly potentiated the benefit of 3,4-diaminopyridine.