Therapeutic Drug Monitoring enables determination of personalized treatment regimen created for individuals by determination of plasma concentrations of drugs in bodily fluids. Such regimens take into account pharmacokinetic and pharmacodynamic variability, thus ensuring the highest effectiveness of therapy and the least chance of toxic or side effects, as well as relapse.
In master thesis we developed the analytical method for determination of antidepressants desvenlafaxine, duloxetine, mirtazapine, sertraline and venlafaxine. Spiked plasma samples were alkanized and paroxetine was added as internal standard. Analytes were extracted with liquid-liquid extraciton with solvent ethyl acetate:cyclohexane 1:9 (v/v), evaporated and reconstituted with acetonitrile:phosphate buffer 1:9 (v/v).
Chromatographic separation was achieved using reversed phase column. Mobile phase was delivered at 1,2 ml/min with gradient program, with run time of developed method 20 minutes. UV-VIS detection was performed at wavelenght 226 nm for desvenlafaxine and venlafaxine, 230 nm for duloxetine, 290 for paroxetine and at 220 nm for sertraline. Mirtazapine was detected with fluorescence detector (λex 290 nm / λem 370 nm).
Developed analytical method was successfully validated for determination of desvenlafaxine, duloxetine and mirtazapine, according to EMA guideline on bioanalytical method validation. Ranges were 10 – 300 ng/ml for desvenlafaxine, 5 – 200 ng/ml for duloxetine and 10 – 200 ng/ml for mirtazapine. Method is selective, accurate and precise within-run and between-run for these three analytes. Stability in autosampler at 10°C was less than 6 hours for desvenlafaxine, at least 24 hours for duloxetine and 6 hours for mirtazapine. Method was not successfully validated for determination of sertraline and venlafaxine.
Based on successful recoveries of extraction, separation on the column and validation we can conclude that the developed method for plasma concentration determination of desvenlafaxine, duloxetine and mirtazapine is suitable for use in TDM.
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