Determination of metoprolol, and its four metabolites in dog plasma.

Metoprolol and its metabolites alpha-hydroxymetoprolol, O-desmethylmetoprolol, metoprolol acid and deaminated metoprolol were quantified in dog plasma using an isocratic high-performance liquid chromatographic method (with a BetaBasic Cyano column) with fluorescence detection. A solid phase extraction technique (Oasis HLB, Waters) was used to extract metoprolol and its four metabolites from dog plasma with high recovery rates. The method was shown to be sensitive and reproducible and was used to determine the pharmacokinetic profile of metoprolol in dog. To the best of our knowledge, this is the only method that can extract and analyze metoprolol and its four metabolites in a single assay.