Extraction techniques for analysis of venlafaxine and its metabolites in biological matrices

Venlafaxine (VEN), which was introduced into therapy in 1990s is one of the most often used antidepressants. The monitoring of its concentration in the organism is recommended, particularly in the case when a patient suffers of others illnesses and is treated with different drugs, which can interfere with VEN. The most popular diagnostic material for the determination of VEN level is blood. The present study is the review of actual reports on the methods of extraction of VEN and its metabolite from blood and other human diagnostic materials, like saliva and urine, and also from animals tissues. The paper shows the classic extraction methods, such as liquid-liquid extraction and solid-phase extraction. It also contains the modifications of these methods such as liquid-phase microextraction and cloud point extraction. According to the literature it can be stated that the best recovery of VEN and its main metabolite, O-demethylvenlafaxine, was obtained when the liquid-liquid extraction was used. The new, modified methods of extraction, are cost-effective, owing to the reduced use of solvents and also smaller volume of diagnostic material, but the results of the analysis, especially the recovery of the analytes, were lower than those obtained by classic methods of extraction.