Determination of 3,4-diaminopyridine in human plasma by high-performance liquid chromatography.

3,bDiaminopyridine (3,4-DAP) is an effective drug in improving neuromuscular transmission. with limited CNS toxicity, compared to its analogue, 4 aminopyridine (4-AP). 3,4DAP is used in the treatment of neuromuscular diseases, such as Lambert-Eaton Syndrome [ 11. A number of HPLC methods for the quantitation of 3,4-DAP and the related 4-AP have been reported. The method of 3,4-DAP quantification in the supernatant after precipitation of serum proteins described by Lamiable and Millart [2] lacks the sensitivity (limit of detection 100 ng ml-‘) required for the measurement of the plasma drug concentrations following therapeutic dosing. Extraction of the drug by organic solvents as described by Uges and Bouma [3] and Shinohara et al. [4] also lack in precision and accuracy, due to the volatile nature of the drug. The two other HPLC methods described by Leslie and Bever [5], and van der Horst et ul. [6] use solid-phase extraction, but the socalled internal standard is added after the drug is extracted. Here we report a sensitive and reproducible method for the measurement of 3,4-DAP in plasma which utilizes solid-phase extraction of both the drug and the internal standard simultaneously, followed by reversedphase ion pair isocratic high-performance liquid chromatography. Materials and Methods