Citalopram (CITA) is available as a racemic mixture and as a pure enantiomer. Its antidepressive action is related to the (+)-(S)-CITA and to the metabolite (+)-(S)-demethylcitalopram (DCITA). In the present investigation, a method for the analysis of CITA and DCITA enantiomers in human and rat plasma was developed and applied to the study of pharmacokinetics. Plasma samples (1 ml) were extracted at pH 9.0 with toluene:isoamyl alcohol (9:1, v/v). The CITA and DCITA enantiomers were analyzed by LC-MS/MS on a Chiralcel OD-R column. Recovery was higher than 70% for both enantiomers. The quantification limit was 0.1 ng/ml, and linearity was observed up to 500 ng/ml plasma for each CITA and DCITA enantiomer. The method was applied to the study of the kinetic disposition of CITA administered in a single oral dose of 20 mg to a healthy volunteer and in a single dose of 20 mg/kg (by gavage) to Wistar rats (n = 6 for each time). The results showed a higher proportion of the (-)-(R)-CITA in human and rat plasma, with S/R AUC ratios for CITA of 0.28 and 0.44, respectively. S/R AUC ratios of DCITA were 0.48 for rats and 1.04 for the healthy volunteer.

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.

Specific RI should be considered for PCV and selected plasma variables in small-sized dogs.

No abstract

No abstract

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT• Citalopram (CITA) pharmacokinetics are enantioselective in healthy volunteers and the metabolism of (+)-(S)-CITA to (+)-(S)-DCITA is dependent on CYP2C19.Omeprazole is a potent CYP2C19 inhibitor. WHAT THIS STUDY ADDS• This study indicates that omeprazole induces a loss of enantioselectivity in the CITA pharmacokinetics because of the selective inhibition of (+)-(S)-CITA metabolism. AIMThe study assessed the influence of omeprazole on the kinetic disposition of the (+)-(S)-citalopram (CITA) and (-)-(R)-CITA enantiomers in healthy volunteers. METHODSIn a cross-over study, healthy volunteers (n = 9) phenotyped as extensive metabolizers of CYP2C19 and CYP2D6 and with an oral midazolam clearance ranging from 10.9 to 149.3 ml min -1 kg -1 received a single dose of racemic CITA (20 mg orally) in combination or not with omeprazole (20 mg day -1 for 18 days). Serial blood samples were collected up to 240 h after CITA administration. CITA and demethylcitalopram (DCITA) enantiomers were analyzed by LC-MS/MS using a Chiralcel® OD-R column. RESULTSThe kinetic disposition of CITA was enantioselective in the absence of treatment with omeprazole, with the observation of a greater proportion of plasma (-) CONCLUSIONSThe administration of multiple doses of omeprazole preferentially inhibited (+)-(S)-CITA metabolism in healthy volunteers. Although omeprazole increased plasma concentrations of (+)-(S)-CITA by approximately 120%, it is difficult to evaluate the clinical outcome because the range of plasma CITA concentrations related to maximum efficacy and minimum risk of adverse effects has not been established.

No abstract

The present study assessed the effect of systemic lupus erythematosus (SLE) activity, a chronic and inflammatory autoimmune disease, on the sinusoidal uptake transporter OATP1B1 using atorvastatin (ATV) as a probe drug. Fifteen healthy subjects, 13 patients with controlled SLE (SLEDAI 0–4), and 12 patients with uncontrolled SLE (SLEDAI from 6 to 15), all women, were investigated. Apparent total clearance of midazolam (MDZ), a marker of CYP3A4 activity, did not vary among the three investigated groups. The controlled and uncontrolled SLE groups showed higher plasma concentrations of MCP‐1 and TNF‐α, while the uncontrolled SLE group also showed higher plasma concentrations of IL‐10. The uncontrolled SLE group showed higher area under the curve (AUC) for ATV (60.47 (43.76–83.56) vs. 30.56 (22.69–41.15) ng⋅hour/mL) and its inactive metabolite ATV‐lactone (98.74 (74.31–131.20) vs. 49.21 (34.89–69.42) ng⋅hour/mL), and lower apparent total clearance (330.7 (239.30–457.00) vs. 654.5 (486.00–881.4) L/hour) and apparent volume of distribution (2,609 (1,607–4,234) vs. 7,159 (4,904–10,450) L), when compared to the healthy subjects group (geometric mean and 95% confidence interval). The pharmacokinetics of ATV and its metabolites did not differ between the healthy subject group and the patients with controlled SLE group. In conclusion, uncontrolled SLE increased the systemic exposure to both ATV and ATV‐lactone, inferring inhibition of OATP1B1 activity, once in vivo CYP3A4 activity assessed by oral clearance of MDZ was unaltered. The inflammatory state, not the disease itself, was responsible for the changes described in the uncontrolled SLE group as a consequence of inhibition of OATP1B1, because systemic exposure to ATV and its metabolites were not altered in patients with controlled SLE.