Simultaneous quantitation of venlafaxine and its main metabolite, O-desmethylvenlafaxine, in human saliva by HPLC.

Venlafaxine is used for the treatment of major depression and generalized anxiety disorders. Because its active metabolite, O-desmethylvenlafaxine, has also a similar activity, the purpose of this work was to develop a simple method for simultaneous quantitation of both drugs using HPLC with UV detection. The saliva was chosen as diagnostic material because of its easy accessibility and possibility of sampling by patients, for example, at home. The sample pretreatment by liquid-liquid extraction allows to separate both compounds from this diagnostic material with a high recovery, varying between 92.65 and 104.78%. The major advantage of the validated method lies in its sensitivity, reproducibility, and specificity for routine quantitation of the venlafaxine and O-desmethylvenlafaxine in the human saliva. The low detection and quantification values (2.8-3.1 and 9.4-10.2 ng/mL, respectively) enable to quantify both species excreted with saliva at the nanogram level. The applicability of the method was verified by analysis of the saliva obtained from depressed women treated with venlafaxine. The results suggest that the method could be used for therapeutic drug monitoring in patients undergoing treatment with venlafaxine, especially when metabolic anomalies or low compliance are suspected, or in the case of polypharmacy.