Degradation of clonazepam in serum by light confirmed by means of a high performance liquid chromatographic method.

The degradation of clonazepam (CZP) in serum during exposure to light can markedly decrease the concentration of the drug. Decay of CZP was studied after exposure to artificial UV light, sunlight, and room light. Serum was extracted with diethylether at pH 9.1. A reversed-phase (RP-8) column was used, with acetonitrile and water as the mobile phase. CZP was detected at 320 nm. The linearity of this high performance liquid chromatographic method is guaranteed to at least 700 nM. The recovery of CZP was 93%, and the day-to-day coefficients of variation were 7.7% (at 75.0 nM) and 6.0% (at 211.4 nM), respectively.