TRACE DECOMPOSITION OF SELEGILINE - USE OF WORST-CASE KINETICS FOR A STABLE DRUG

A solution of selegiline hydrochloride reference standard, which conta ined no detectable impurities at the time of its preparation, was foun d by HPLC to contain a trace of a compound at the locus of methampheta mine when analyzed after 1 year. Heating selegiline solutions at pH 7 and 105 degrees C produced methamphetamine as the major product at a r ate which closely followed the first-order rate equation. Using only t hese data and worst-case assumptions, rate constants were estimated at various temperatures; the activation energy was estimated to be about 25 kcal, and the stability-indicating validity of the assay used was reaffirmed. Selegiline undergoes degradation at a negligibly slow rate .