highperformance liquid chromatographic determination of tramadol and its odesmethylated metabolite in blood plasma application to a bioequivalence study in humans simultaneous hplc determination of the analgetic agent tramadol its major pharmacodynamically active metabolite odesmethyltramadol in human plasma is described simple methods for the preparation of the standard of the abovementioned tramadol metabolite and n1n1dimethylsulfanilamide used as the internal standard are also presented the analytical procedure involved a simple liquidliquid extraction of the analytes from the plasma under the conditions described previously hplc analysis was performed on a 250x4 mm chromatographic column with lichrospher 60 rpselectb 5microm merck and consists of an analytical period where the mobile phase acetonitrile001 m phosphate buffer ph 28 37 vv was used and of a subsequent washout period where the plasmatic ballast compounds were eluted from the column using acetonitrileultrahighquality water 82 vv the whole analysis including the equilibration preceding the initial analytical conditions lasted 19 min fluorescence detection lambdaex 202 nmlambdaem 296 nm for tramadol and its metabolite lambdaex 264 nmlambdaem 344 nm for n1n1dimethylsulfanilamide was used the validated analytical method was applied to pharmacokinetic studies of tramadol in human volunteers