HPLC method for determination of 3,4-diaminopyridine in the presence of related substances and degradation products formed under stress conditions

3,4-Diaminopyridine is used to treat some symptoms met in Lambert Eaton myasthenia syndrome. It was shown efficient to reduce a form of variable muscle weakness and fatigability typical of the disease and correlated to a block of acetylcholine release. A high performance liquid chromatographic method for the determination of 3,4-diaminopyridine in the presence of related substances and its degradation products is described. The method is based on the use of a C18 bonded phase column and a mobile phase composed of 10 volumes of acetonitrile and 90 volumes of an aqueous solution containing 1 g L-1 sodium octanesulfonate and 0.77 g L-1 ammonium acetate. The pH of the aqueous solution was adjusted to 1.9 with trifluoracetic acid. All peaks are eluted in < 40 min. The method was demonstrated to be precise, accurate and specific even though a major part of the drug is decomposed. The results indicate that the proposed method could be used in stability assays.