Nifedipine Does Not Alter the Pharmacokinetics of Venlafaxine Enantiomers in Healthy Subjects Phenotyped for CYP2D6, CYP2C19, and CYP3A.

Venlafaxine (VEN) is a P-glycoprotein (P-gp) substrate, and nifedipine has been described by in vitro and experimental studies as a P-gp inhibitor. The present study aimed to investigate whether nifedipine alters the kinetic disposition of VEN enantiomers and their metabolites in healthy subjects. A crossover study was conducted in 10 healthy subjects phenotyped as extensive metabolizers for cytochrome P450 (CYP) 2D6, CYP2C19, and CYP3A. In phase 1, the subjects received a single oral dose of 150 mg racemic VEN, and in phase 2, a single oral dose of 40 mg nifedipine was administered with the VEN treatment. Plasma concentrations of VEN enantiomers and their metabolites O-desmethylvenlafaxine and N, O- didesmethylvenlafaxine (ODV and DDV, respectively) were evaluated by liquid chromatography with tandem mass spectrometry up to 72 hours after drug administration. Phase 2 was compared with phase 1 using the 90% confidence interval (CI) of the ratio of geometric means for Cmax and area under the curve (AUC). AUC enantiomeric ratios S-(+)/R-(-) were evaluated within each and between phases using the Wilcoxon test (P ≤ .05). The kinetic disposition of VEN was enantioselective (phase 1) with VEN S-(+)/R-(-) AUC ratio median of 2.83 (AUC0-∞ , 526 vs 195 ng·h/mL). However, AUC median did not differ between enantiomers for the metabolites ODV (1971 vs 2226 ng·h/mL) and DDV (199 vs 151 ng·h/mL). The 90%CI of the ratio of geometric means showed that the phases are bioequivalent. A single oral dose of 40 mg nifedipine did not alter VEN enantiomer pharmacokinetics in healthy subjects.

Selective solid-phase extraction using molecularly imprinted polymers for analysis of venlafaxine, O-desmethylvenlafaxine, and N-desmethylvenlafaxine in plasma samples by liquid chromatography-tandem mass spectrometry.

This paper focuses on the development of a novel miniaturized molecularly imprinted solid-phase extraction (MISPE) and ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method to determine venlafaxine (VEN), O-desmethylvenlafaxine (ODV), and N-desmethylvenlafaxine (NDV) in plasma samples. The molecularly imprinted polymer (MIP) was prepared by the precipitation polymerization approach; VEN, metacrylic acid, ethylene glycol dimethacrylate, 2,2-azobisisobutyronitrile, and toluene were used as template, monomer, crosslinker, initiator, and porogen solvent, respectively. MIP and of the non-imprinted control polymer (NIP) sorbents were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. MIP phase presented higher extraction efficiency (MISPE, using plasma samples spiked with VEN) than the NIP phase (84 and 49% recovery rates, respectively). Analysis of other antidepressants with different chemical structures by MISPE-UHPLC-MS/MS attested to the selectivity of the developed MIP. The developed method presented precision assays with coefficients of variation (CV) smaller than 15%; accuracy assays with relative standard error (RSE%) values ranging from -12 to 16%, and linear ranges from 3 to 700ngmL(-1) for VEN, from 5 to 700ngmL(-1) for ODV, and from 3 to 500ngmL(-1) for NDV. The coefficients of determination (r(2)) were higher than 0.995. The lack-of-fit test also attested to the linearity of this method. This method was successfully applied to determine VEN, NDV, and ODV in plasma samples from depressed patients undergoing therapy with VEN.

Pharmacokinetics of venlafaxine enantiomers and their metabolites in psoriasis patients.

Psoriasis is a chronic inflammatory disease associated with several comorbidities, including depression. Previous studies have shown that inflammatory diseases downregulate the expression and suppress activity of CYP isoforms. Venlafaxine (VLX) is an antidepressant metabolized mainly by CYP2D6 to O-desmethylvenlafaxine (ODV), CYP3A to N-desmethylvenlafaxine (NDV), and CYP2D6 and CYP3A to N,O-didesmethylvenlafaxine (DDV). This study evaluated the influence of psoriasis on the enantioselective pharmacokinetics of VLX. Psoriasis patients (n = 13) and healthy volunteers (n = 11) phenotyped as CYP2D6 extensive (EM) or poor metabolizers (n = 1) received a single oral dose of 150 mg racemic VLX. Plasma concentrations of TNF-α, IFN-γ, IL-6, IL-8, and IL-17 cytokines were higher in EM psoriasis patients when compared with healthy volunteers. IL-6 plasma concentrations varied from 0.4 to 12.9 pg/mL (mean, 2.1 pg/mL) in healthy volunteers and from 0.4 to 29.3 pg/mL (mean, 4.2 pg/mL) in psoriatic patients. VLX pharmacokinetics are enantioselective in healthy volunteers and psoriasis patients phenotyped as EM. Higher AUC values for the (S)-VLX, (S)-NDV, and (S)-DDV enantiomers were observed in healthy volunteers, whereas higher AUC values for (S)-VLX and (R)-ODV were found in psoriasis patients phenotyped as EM. Psoriasis does not alter the pharmacokinetics of the VLX enantiomers probably because of the low levels of IL-6 plasma concentrations.