Determination of specific absorbance (A|) for Zaleplon (Sonata) by spectrophotometry.

Specific absorbance (A|) is the maximum absorbance of a 1% solution over a 1-cm path length as measured by a spectrophotometer. If a reliable A| determination is available for a drug, it provides an extremely useful tool for the quantitative verification of a stock drug solution. Zaleplon was introduced into the market in 1999, and although the drug has been available for 10 years, A| has not been published in the literature. Zaleplon's A| was experimentally determined by a spectrophotometer at 229 nm in aqueous acid and verified with three independent external sources to be 1186 (1042-1262; n = 18). The experimentally determined A| of zaleplon is beneficial to a toxicology laboratory to verify the quantitative accuracy of a drug solution prior to its use in casework.