Population Pharmacokinetic of the Diterpenes ent-Polyalthic Acid and Dihydro-ent-Agathic Acid from Copaifera Duckei Oil Resin in Rats.

Copaifera duckei oleoresin is a plant product extensively used by the Brazilian population for multiple purposes, such as medicinal and cosmetic. Despite its ethnopharmacological relevance, there is no pharmacokinetic data on this important medicinal plant. Due to this, we determined the pharmacokinetic profile of the major nonvolatile compounds of C. duckei oleoresin. The diterpenes ent-polyalthic acid and dihydro-ent-agathic acid correspond to approximately 40% of the total oleoresin. Quantification was performed using LC-MS/MS, and the validated analytical method showed to be precise, accurate, robust, reliable, and linear between 0.57 and 114.74 µg/mL plasma and 0.09 to 18.85 µg/mL plasma, respectively, for ent-polyalthic acid and dihydro-ent-agathic acid, making it suitable for application in preclinical pharmacokinetic studies. Wistar rats received a single 200 mg/kg oral dose (gavage) of C. duckei oleoresin, and blood was collected from their caudal vein through 48 h. Population pharmacokinetics analysis of ent-polyalthic and dihydro-ent-agathic acids in rats was evaluated using nonlinear mixed-effects modeling conducted in NONMEN software. The pharmacokinetic parameters of ent-polyalthic acid were absorption constant rate = 0.47 h-1, central and peripheral apparent volume of distribution = 0.04 L and 2.48 L, respectively, apparent clearance = 0.15 L/h, and elimination half-life = 11.60 h. For dihydro-ent-agathic acid, absorption constant rate = 0.28 h-1, central and peripheral apparent volume of distribution = 0.01 L and 0.18 L, respectively, apparent clearance = 0.04 L/h, and elimination half-life = 3.49 h. The apparent clearance, central apparent volume of distribution, and peripheral apparent volume of distribution of ent-polyalthic acid were approximately 3.75, 4.00-, and 13.78-folds higher than those of dihydro-ent-agathic.

Optimizing Therapeutic Drug Monitoring in Pregnant Women: A Critical Literature Review.

BACKGROUND: More than 90% of pregnant women take at least one drug during pregnancy. Drug dose adjustments during pregnancy are sometimes necessary due to various pregnancy-induced physiological alterations frequently associated with lower plasma concentrations. However, the clinical relevance or benefits of therapeutic drug monitoring (TDM) in pregnant women have not been specifically studied. Clinical pharmacokinetic studies in pregnant women are incredibly challenging for many reasons. Despite this, regulatory agencies have made efforts to encourage the inclusion of this population in clinical trials to achieve more information on the pharmacotherapy of pregnant women. This review aims to provide support for TDM recommendations and dose adjustments in pregnant women. METHODS: The search was conducted after a predetermined strategy on PubMed and Scopus databases using the MeSH term "pregnancy" alongside other terms such as "Pregnancy and dose adjustment," "Pregnancy and therapeutic drug monitoring," "Pregnancy and PBPK," "Pregnancy and pharmacokinetics," and "Pregnancy and physiological changes." RESULTS: The main information on TDM in pregnant women is available for antiepileptics, antipsychotics, antidepressants, antibiotics, antimalarials, and oncologic and immunosuppressive drugs. CONCLUSIONS: More data are needed to support informed benefit-risk decision making for the administration of drugs to pregnant women. TDM and/or pharmacokinetic studies could ensure that pregnant women receive an adequate dosage of an active drug. Mechanistic modeling approaches potentially could increase our knowledge about the pharmacotherapy of this special population, and they could be used to better design dosage regimens.

Pharmacogenetic predictors of variability in efavirenz pharmacokinetics in an admixed Brazilian HIV cohort.

AIMS: To investigate the influence of pharmacogenetic polymorphisms on efavirenz (EFV) exposure and metabolism in HIV-infected Brazilians under treatment with EFV-containing antiretroviral (ART) regimens. METHODS: HIV-positive adults (n = 82) on stable ART regimens containing 600 mg EFV once daily for at least 6 months were recruited at 2 university hospitals. Blood samples collected at mid-dose interval were used to quantify the plasma concentrations of EFV (denoted [EFV]), its major metabolite 8-OH-EFV ([8-OH-EFV]) and [8-OH-EFV]/[EFV] metabolic ratio, and to genotype single nucleotide polymorphisms in CYP2B6 (rs3745274, c.516G > T; rs28399499, c.983 T > C) and ABCB1 (rs3842, c.4036G > A). CYP2B6 metabolic phenotypes were inferred from the CYP2B6 diplotypes. Linear regression modelling was applied to identify sociodemographic, clinical and pharmacogenetic predictors of [EFV] and [8-OH-EFV]/[EFV] metabolic ratio. RESULTS: Wide (50-fold) interindividual variation in [EFV], [8-OH-EFV] and [8-OH-EFV]/[EFV] was observed; 69.5% of participants had [EFV] within the nominal therapeutic range (1000-4000 ng/mL), while 19.5 and 11.0% had [EFV] below and above this range, respectively. Multiple regression modelling retained only CYP2B6 metabolic phenotypes or the combined rs3745274 and rs28399499 genotypes, as significant predictors of [EFV] and [8-OH-EFV]/[EFV]. CONCLUSION: EFV exposure and disposition varied widely among HIV-infected Brazilians under stable treatment with EFV-containing ART regimens. About 1/10 of the participants had [EFV] exceeding nominal supratherapeutic concentration (4000 ng/mL), but reported tolerance to the ARV regimens, while 1/5 of participants had nominal subtherapeutic [EFV] (<1000 ng/mL) but adequate virological response. Genotype for the 2 CYP2B6 single nucleotide polymorphisms studied explained 48% of variation in [EFV] and 35% of variation in [8-OH-EFV]/[EFV].

Enhanced elimination of betamethasone in dichorionic twin pregnancies.

AIM: No study has evaluated the betamethasone pharmacokinetics in twin pregnancies according to chorionicity. This study aimed to describe and compare the betamethasone pharmacokinetic parameters in singleton and dichorionic (DC) and monochorionic twin pregnancies in the third trimester of pregnancy. METHODS: Twenty-six pregnant women received 2 intramuscular doses of 6 mg of betamethasone sodium phosphate plus 6 mg betamethasone acetate due to preterm labour. Serial blood samples were collected for 24 hours after the first intramuscular dose of betamethasone esters. Betamethasone plasma concentrations were quantified using a validated liquid chromatography-tandem mass spectrometry analytical method, and the pharmacokinetic parameters were obtained employing a noncompartmental model. Preliminary data on the betamethasone placental transfer are also presented. RESULTS: The geometric mean (95% confidence interval) of AUC0-∞ 645.1 (504.3-825.2) vs. 409.8 (311.2-539.6) ng.h/mL and CL/F 17.70 (13.84-22.65) vs. 27.87 (21.17-36.69) were significantly different, respectively, in singleton pregnancies when compared to DC twins. CONCLUSION: Data from this study suggest that the presence of 2 foetoplacental units may increase the betamethasone metabolism by hepatic CYP3A4 and/or placental 11ß-HSD2 enzymes. Pharmacokinetic-pharmacodynamic clinical studies are needed to investigate whether these betamethasone pharmacokinetic changes have clinical repercussions for the newborns and require dose adjustment in DC twin pregnancies.

Clinical treatment for hepatitis C reverses CYP2C19 inhibition.

AIMS: Infection by the hepatitis C virus (HCV) generates inflammatory response selectively modulating cytochrome P450 protein (CYP) activities. This study assessed the effect of chronic hepatitis C on CYP2C19 activity in patients with HCV. METHODS: Patients with HCV infection (n = 23) at different fibrosis stages were allocated into groups 1 (F0/F1 and F2, mild to moderate fibrosis) and 2 (F3 and F4, advanced fibrosis stages). Phase 1 was conducted before the treatment with direct-acting antivirals (DAAs) and phase 2 after the sustained virological response. Participants were administered 2 mg of a single oral dose of omeprazole (OME) as probe drug in both phases. Metabolic ratios (MRs) (plasma samples collected at 4 h after OME administration) were calculated by dividing plasma concentrations of 5-hydroxyomeprazole by OME. RESULTS: The MRs for group 1 were 0.45 (0.34-0.60, 90% confidence interval) and 0.69 (0.50-0.96) for phases 1 and 2, respectively, while the MRs for group 2 were 0.25 (0.21-0.31) and 0.41 (0.30-0.56) for phases 1 and 2, respectively. MRs were different (P < .05) between phases 1 and 2 for both groups, as well as between groups 1 and 2 in phase 1, but not in phase 2 (P > .05). CONCLUSIONS: Both groups presented different MRs before and after treatment with DAAs, evidencing that CYP2C19 inhibition during inflammation was at least partially reversed after DAA treatment. Groups 1 and 2 were also found to be different in phase 1 but not phase 2, showing that CYP2C19 metabolic activity does not differ between groups after DAA treatment.

Impact of Plasmodium vivax malaria and antimalarial treatment on cytochrome P450 activity in Brazilian patients.

AIMS: To investigate the impact of Plasmodium vivax malaria and chloroquine-primaquine chemotherapy on CYP2D6 and CYP2C19 activity in patients from the Brazilian Amazon. METHODS: Adult patients (n = 30) were given subtherapeutic doses of CYP2D6 and CYP2C19 phenotypic probes metoprolol (10 mg) and omeprazole (2 mg) in three different stages of vivax malaria illness: acute disease (study phase 1), post chemotherapy (phase 2) and convalescence (stage 3). Plasma concentrations of probes and CYP-hydroxylated metabolites (α-OH metoprolol and 5-OH omeprazole) were measured using LC/MS/MS. Two pharmacokinetic metrics were used to estimate CYP activity: (a) ratio of plasma concentrations of probe/metabolite at 240 minutes after administration of the probes and (b) ratio of areas under the time-concentration curves for probe/metabolite (AUC0-12h ). For statistical analysis, the pharmacokinetic metrics were normalized to the respective values in phase 3. Taqman assays were used for CYP2D6 and CYP2C19 genotyping. Cytokines levels were measured using cytometric bead array. RESULTS: Both pharmacokinetic metrics for metoprolol and omeprazole, and plasma concentrations of cytokines IL-6, IL-8 and IL-10 varied significantly across the three study phases (ANOVA P < 0.0001). Post hoc tests showed greater metoprolol:α-OH metoprolol ratios in phases 1 and 2 compared to phase 3, larger omeprazole:5-OH omeprazole ratios in phase 1 than in phases 2 and 3, and higher circulating IL-6, IL-8 and IL-10 in phase 1 than in phases 2 and 3. CONCLUSION: P. vivax malaria and treatment altered CYP2D6 and CYP2C19 metabolic phenotypes. CYP2C19 inhibition is attributed to a higher level of circulating proinflammatory cytokines, while suppression of CYP2D6 is ascribed mainly to chloroquine exposure.

Chiral Transplacental Pharmacokinetics of Fexofenadine: Impact of P-Glycoprotein Inhibitor Fluoxetine Using the Human Placental Perfusion Model.

PURPOSE: Fexofenadine is a well-identified in vivo probe substrate of P-glycoprotein (P-gp) and/or organic anion transporting polypeptide (OATP). This work aimed to investigate the transplacental pharmacokinetics of fexofenadine enantiomers with and without the selective P-gp inhibitor fluoxetine. METHODS: The chiral transplacental pharmacokinetics of fexofenadine-fluoxetine interaction was determined using the ex vivo human placenta perfusion model (n = 4). In the Control period, racemic fexofenadine (75 ng of each enantiomer/ml) was added in the maternal circuit. In the Interaction period, racemic fluoxetine (50 ng of each enantiomer/mL) and racemic fexofenadine (75 ng of each enantiomer/mL) were added to the maternal circulation. In both periods, maternal and fetal perfusate samples were taken over 90 min. RESULTS: The (S)-(-)- and (R)-(+)-fexofenadine fetal-to-maternal ratio values in Control and Interaction periods were similar (~0.18). The placental transfer rates were similar between (S)-(-)- and (R)-(+)-fexofenadine in both Control (0.0024 vs 0.0019 min-1) and Interaction (0.0019 vs 0.0021 min-1) periods. In both Control and Interaction periods, the enantiomeric fexofenadine ratios [R-(+)/S-(-)] were approximately 1. CONCLUSIONS: Our study showed a low extent, slow rate of non-enantioselective placental transfer of fexofenadine enantiomers, indicating a limited fetal fexofenadine exposure mediated by placental P-gp and/or OATP2B1. The fluoxetine interaction did not affect the non-enantioselective transplacental transfer of fexofenadine. The ex vivo placental perfusion model accurately predicts in vivo placental transfer of fexofenadine enantiomers with remarkably similar values (~0.17), and thus estimates the limited fetal exposure.

Chiral Discrimination of P-glycoprotein in Parturient Women: Effect of Fluoxetine on Maternal-Fetal Fexofenadine Pharmacokinetics.

BACKGROUND AND OBJECTIVE: Fluoxetine, antidepressant widely-used during pregnancy, is a selective inhibitor for P-glycoprotein (P-gp). Fexofenadine, an in vivo P-gp probe, is an antihistamine drug for seasonal allergic rhinitis and chronic urticaria treatment during pregnancy and it is available as a racemic mixture. This study evaluated the chiral discrimination of P-gp investigating the effect of fluoxetine on maternal-fetal pharmacokinetics of fexofenadine. METHODS: Healthy parturient women received either a single oral dose of 60 mg racemic fexofenadine (Control group; n = 8) or a single oral dose of 40 mg racemic fluoxetine 3 h before a single oral dose of 60 mg racemic fexofenadine (Interaction group; n = 8). Maternal blood and urine samples were collected up to 48 h after fexofenadine administration. At delivery, maternal-placental-fetal blood samples were collected. RESULTS: The maternal pharmacokinetics of fexofenadine was enantioselective (AUC0-∞R-(+)/S-(-) ~ 1.5) in both control and interaction groups. Fluoxetine increased AUC0-∞ (267.7 vs 376.1 ng.h/mL) and decreased oral total clearance (105.1 vs 74.4 L/h) only of S-(-)-fexofenadine, whereas the renal clearance were reduced for both enantiomers, suggesting that the intestinal P-gp-mediated transport of S-(-)-fexofenadine is influenced by fluoxetine to a greater extent that the R-(+)-fexofenadine. However, the transplacental transfer of fexofenadine is low (~16%), non-enantioselective and non-influenced by fluoxetine. CONCLUSIONS: A single oral dose of 40 mg fluoxetine inhibited the intestinal P-gp mediated transport of S-(-)-fexofenadine to a greater extent than R-(+)-fexofenadine in parturient women. However, the placental P-gp did not discriminate fexofenadine enantiomers and was not inhibited by fluoxetine.

Lopinavir/ritonavir treatment increases the placental transfer of bupivacaine enantiomers in human immunodeficiency virus-infected pregnant women.

AIMS: The present study evaluated the placental transfer and amniotic fluid distribution of bupivacaine enantiomers in health pregnant women and in human immunodeficiency virus (HIV)-infected pregnant women receiving epidural anaesthesia for caesarean section. METHODS: Twelve HIV-infected pregnant women (HIV group) were treated long-term (at least 8 weeks) with lopinavir/ritonavir (400/100 mg twice daily), and 12 healthy pregnant women (Control group) who submitted to epidural anaesthesia with racemic bupivacaine (75 mg) during caesarean section were investigated. At delivery, samples of maternal and fetal blood and amniotic fluid were collected (10-20 min after drug administration). RESULTS: The placental transfer ratio of bupivacaine enantiomers was significantly higher among the pregnant women from the HIV group when compared with those from the Control group (Mann-Whitney test, P ≤ 0.05). Placental transfer ratios (median and 25th - 75th percentiles) for (+)-(R)-bupivacaine were 0.58 (0.38-0.82) in the HIV group vs. 0.25 (0.18-0.33) in the Control group, and for (-)-(S)-bupivacaine, they were 0.54 (0.34-0.69) in the HIV group vs. 0.25 (0.19-0.29) in the Control group. The transplacental distribution of bupivacaine was stereoselective only in the HIV group. The umbilical artery/umbilical vein ratio and amniotic fluid/maternal vein ratio were low and nonstereoselective, and no statistically significant differences were observed between the groups. CONCLUSIONS: This study supports that the placental transfer of both bupivacaine enantiomers was 100% higher in HIV-pregnant women treated with lopinavir/ritonavir when compared with that in healthy pregnant women receiving epidural anaesthesia for caesarean section.

Therapeutic Doses of Eltrombopag do not Inhibit Hepatic BCRP in Healthy Volunteers: Intravenous Ceftriaxone as a Model.

PURPOSE: Ceftriaxone elimination occurs through breast cancer resistance transporter (BCRP) and multidrug resistance-associated protein 2 (MRP-2) which are expressed on the canalicular membrane of hepatocytes. Eltrombopag, a thrombopoetin receptor agonist used in the treatment of immune thrombocytopenic purpura, is reported in in vitro studies as an inhibitor of intestinal BCRP but not an inhibitor of hepatic BCRP. Thus, the present study evaluates the effect of therapeutic doses of eltrombopag on the clinical pharmacokinetics of intravenous ceftriaxone. METHODS: Healthy adult (n=12) were treated with oral doses of eltrombopag (0, 25 or 50 mg) 28 and 4 h prior to intravenous ceftriaxone administration (1g). Serial blood samples were collected up to 48 h after ceftriaxone administration and plasma samples were analysed by LC-MS/MS using 50 µL aliquots (total concentration) and 100 µL (unbound concentration). RESULTS: A method to analyze total and unbound ceftriaxone in plasma using LC-MS/MS was developed and validated with linearity from 1 to 200 µg/mL. Both methods are sensitive, precise and accurate with coefficients of variation less than 15% in the study of inter- and intra-assay precision and accuracy. Ceftriaxone pharmacokinetics in healthy adults were described using a bicompartmental model, with a mean clearance of 0.96 L/h (CI95% 0.71-1.20) and AUC0-∞of 1106 mg.h/mL (CI95% 811-1400) for volunteers that received only ceftriaxone; clearance of 0.95 L/h (CI95% 0.77-1.13) and AUC0-∞ of 1083 mg.h/mL (CI95% 876-1290) for volunteers that received ceftriaxone plus 25 mg of eltrombopag and clearance of 0.96 L/h (CI95% 0.74-1.19) and AUC0-∞ of 1072 mg.h/mL (CI95% 872-1273) for volunteers that received ceftriaxone plus 50 mg of eltrombopag. CONCLUSIONS: The results do not support the existence of a clinical pharmacokinetic drug interaction involving hepatic BCRP in human subjects receiving intravenous ceftriaxone and oral eltrombopag. This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

Effect of type 2 diabetes mellitus on the pharmacokinetics and transplacental transfer of nifedipine in hypertensive pregnant women.

AIMS: Diabetes mellitus can inhibit cytochrome P450 3A4, an enzyme responsible for the metabolism of nifedipine, used for the treatment of hypertension in pregnant women. We aimed to assess the effect of type 2 diabetes mellitus (T2DM) on the pharmacokinetics, placental transfer and distribution of nifedipine in amniotic fluid in hypertensive pregnant women. METHODS: The study was conducted in 12 hypertensive pregnant women [control group (CG)] and 10 hypertensive pregnant women with T2DM taking slow-release nifedipine (20 mg, 12/12 h). On the 34th week of gestation, serial blood samples were collected (0-12 h) after administration of the medication. At delivery, samples of maternal and fetal blood and amniotic fluid were collected for determination of nifedipine distribution in these compartments. RESULTS: The median pharmacokinetic parameters of CG were: peak plasma concentration (Cmax ) 26.41 ng ml-1 , time to reach Cmax (tmax ) 1.79 h, area under the plasma concentration vs. time curve from 0-12 h (AUC0-12 ) 235.99 ng.h ml-1 , half-life (t½) 4.34 h, volume of distribution divided by bioavailability (Vd/F) 560.96 l, and ClT /F 84.77 l h-1 . The parameters for T2DM group were: Cmax 23.52 ng ml-1 , tmax 1.48 h, AUC0-12 202.23 ng.h ml-1 , t½ 5.00 h, Vd/F 609.40 l, and apparent total clearance (ClT /F) 98.94 l h-1 . The ratios of plasma concentrations of nifedipine in the umbilical vein, intervillous space and amniotic fluid to those in the maternal vein for CG and T2DM were 0.53 and 0.44, 0.78 and 0.87, respectively, with an amniotic fluid/maternal plasma ratio of 0.05 for both groups. The ratios of plasma concentrations in the umbilical artery to those in the umbilical vein were 0.82 for CG and 0.88 for T2DM. CONCLUSIONS: There was no influence of T2DM on the pharmacokinetics or placental transfer of nifedipine in hypertensive women with controlled diabetes.

Influence of verapamil on the pharmacokinetics of oxcarbazepine and of the enantiomers of its 10-hydroxy metabolite in healthy volunteers.

PURPOSE: Oxcarbazepine (OXC), a second-generation antiepileptic, and its chiral metabolite 10-hydroxycarbazepine (MHD) are substrates of P-glycoprotein, which can be inhibited by verapamil. This study evaluated the influence of verapamil on the pharmacokinetics of OXC and MHD enantiomers in healthy volunteers. METHODS: Healthy volunteers (n = 12) on occasion O (OXC monotherapy) received 300 mg OXC/12 h for 5 days, and on the O + V occasion (treatment with OXC + verapamil), they received 300 mg OXC/12 h and 80 mg verapamil/8 h for 5 days. Blood samples were collected over a period of 12 h. Total and free plasma concentrations of OXC and the MHD enantiomers were evaluated by LC-MS/MS. Noncompartmental pharmacokinetic analysis was performed using the WinNonlin program. RESULTS: The kinetic disposition of MHD was enantioselective with plasma accumulation (AUC(0-12) S-(+)/R-(-) ratio of 4.38) and lower fraction unbound (0.37 vs 0.42) of the S-(+)-MHD enantiomer. Treatment with verapamil reduced the OXC mean residence time (4.91 vs 4.20 h) and apparent volume of distribution (4.72 vs 3.15 L/kg). Verapamil also increased for both MHD enantiomers C max total [R-(-)-MHD: 2.65 vs 2.98 µg/mL and S-(+)-MHD: 10.15 vs 11.60 µg/mL], C average [R-(-)-MHD: 1.98 vs 2.18 µg/mL and S-(+)-MHD: 8.10 vs 8.83 µg/mL], and AUC(0-12) [R-(-)-MHD: 23.79 vs 26.19 µg h/mL and S-(+)-MHD: 97.87 vs 108.35 µg h/mL]. CONCLUSION: Verapamil increased the AUC values of both MDH enantiomers, which is probably related to the inhibition of intestinal P-glycoprotein. Considering that the exposure of both MHD enantiomers was increased in only 10 %, no OXC dose adjustment could be recommended in the situation of verapamil coadministration.

Influence of gestational diabetes on the stereoselective pharmacokinetics and placental distribution of metoprolol and its metabolites in parturients.

AIM: To investigate the influence of gestational diabetes mellitus (GDM) on the kinetic disposition and transplacental and amniotic fluid distribution of metoprolol and its metabolites O-desmethylmetoproloic acid and α-hydroxymetoprolol stereoisomers in hypertensive parturients receiving a single dose of the racemic drug. METHODS: The study was conducted on hypertensive parturients with well-controlled GDM (n = 11) and non-diabetic hypertensive parturients (n = 24), all receiving a single 100 mg oral dose of racemic metoprolol tartrate before delivery. Serial maternal blood samples (0-24 h) and umbilical blood and amniotic fluid samples were collected for the quantitation of metoprolol and its metabolite stereoisomers using LC-MS/MS or fluorescence detection. RESULTS: The kinetic disposition of metoprolol and its metabolites was stereoselective in the diabetic and control groups. Well-controlled GDM prolonged tmax for both enantiomers of metoprolol (1.5 vs. 2.5 h R-(+)-MET; 1.5 vs. 2.75 h S-(-)-MET) and O-desmethylmetoproloic acid (2.0 vs. 3.5 h R-(+)-AOMD; 2.0 vs. 3.0 h S-(-)-OAMD), and for the four stereoisomers of α-hydroxymetoprolol (2.0 vs. 3.0 h for 1'S,2R-, 1'R,2R- and 1'R,2S-OHM; 2.0 vs. 3.5 h for 1'S,2S-OHM) and reduced the transplacental distribution of 1'S,2S-, 1'R,2R-, and 1'R,2S-OHM by approximately 20%. CONCLUSIONS: The kinetic disposition of metoprolol was enantioselective, with plasma accumulation of the S-(-)-MET eutomer. Well-controlled GDM prolonged the tmax of metoprolol and O-desmethylmetoproloic acid enantiomers and the α-hydroxymetoprolol stereoisomers and reduced by about 20% the transplacental distribution of 1'S,2S-, 1'R,2R-, and 1'R,2S-OHM. Thus, well-controlled GDM did not change the activity of CYP2D6 and CYP3A involved in metoprolol metabolism.

Impact of visceral leishmaniasis and curative chemotherapy on cytochrome P450 activity in Brazilian patients.

AIMS: The aim of the present study was to investigate the impact of human visceral leishmaniasis (VL) and curative chemotherapy on the activity of cytochrome P450 (CYP) 3A, CYP2C9 and CYP2C19 in patients from an endemic region in Brazil. METHODS: Adult patients with parasitologically confirmed VL were given a CYP phenotyping cocktail, comprising midazolam, omeprazole and losartan, immediately before (Study phase 1), 2-3 days (phase 2) and 3-6 months (phase 3) after curative VL chemotherapy. CYP activity was assessed by the apparent clearance of midazolam (CYP3A), omeprazole/5-hydroxyomeprazol ratio in plasma (CYP2C19) and losartan/E3174 ratio in urine (CYP2C9). RESULTS: Mean values (95% confidence interval) in phases 1, 2 and 3 were, respectively: log apparent midazolam clearance, 1.21 (1.10-1.31), 1.45 (1.32-1.57) and 1.35 (1.26-1.44) ml min(-1) kg(-1) ; omeprazole/5-hydroxyomeprazole ratio, 0.78 (0.61-0.94), 0.45 (0.27-0.63) and 0.37 (0.20-0.55); losartan/E3174 ratio, 0.66 (0.39-0.92), 0.35 (0.20-0.50) and 0.35 (0.16-0.53). Analysis of variance revealed significant differences in CYP3A (P = 0.018) and CYP2C19 (P = 0.008), but not CYP2C9 (P = 0.11) phenotypic activity, across the three study phases. CONCLUSION: The phenotypic activities of CYP3A4 and CYP2C19 were significantly reduced during acute VL compared with post-chemotherapy. We propose that increased plasma concentrations of proinflammatory cytokines during active disease account for the suppression of CYP activity. The failure to detect significant changes in CYP2C9 activity in the overall cohort may reflect differential effects of the inflammatory process on the expression of CYP isoforms, although the possibility of insufficient statistical power cannot be dismissed.

Analysis of ibuprofen enantiomers in rat plasma by liquid chromatography with tandem mass spectrometry.

A sensitive and selective method for the analysis of ibuprofen enantiomers by LC-MS/MS was developed and validated for the purpose of application in pharmacokinetic studies in small experimental animals. Aliquots of 200 µL plasma were submitted to liquid-liquid extraction with hexane/diisopropylether (50:50 v/v) in acid pH. Separation was accomplished in a Chirex® 3005 (250 × 4.6 mm, 5 µm) column at 25°C with a mobile phase that consisted of 0.01 M ammonium acetate in methanol at a flow rate of 1.1 mL/min. The mass spectrometer consisted of an ESI interface operating at negative ionization mode and multiple reaction monitoring. The transitions 205 > 161 and 240 > 197 were monitored for ibuprofen enantiomers and fenoprofen (internal standard), respectively. Method validation included the evaluation of the matrix effect, stability, linearity, lower LOQ, within-run and between-run precision, and accuracy. The lower LOQ was 25 ng/mL for each ibuprofen enantiomer, and the calibration curves showed good linearity in the range 0.025-50 µg/mL. The method was successfully applied in the investigation of pharmacokinetic disposition of ibuprofen enantiomers in rats treated orally with 25 mg/kg of the racemate. Enantioselective kinetic disposition was observed with accumulation of (+)-(S)-ibuprofen in rats following single oral administration.

Intestinal P-gp activity is reduced in postmenopausal women under breast cancer therapy.

Intestinal P-glycoprotein (P-gp) activity plays a crucial role in modulating the oral bioavailability of its substrates. Fexofenadine has commonly been used as a P-gp probe, although it is important to note the involvement of other drug transporters like, OATP1B1, OATP1B3, and OATP2B1. In vitro studies demonstrated an upregulation of P-gp protein in response to exposure to pregnancy-related hormones. The objective of this study was to investigate how intestinal P-gp activity is impacted by menopausal status. This study sampled fexofenadine plasma concentrations over 0-12 h after probe drug administration from two groups of patients with breast cancer: premenopausal (n = 20) and postmenopausal (n = 20). Fexofenadine plasma concentrations were quantified using liquid-chromatography tandem mass spectrometry. Area under the plasma concentration-time curve from zero to infinity (AUCinf ) was calculated through limited sampling strategies equation. Multiple linear regression was applied on AUCinf , maximum plasma concentration (Cmax ), and time to Cmax . Postmenopausal patients showed a significant increase in Cmax (geometric mean and 95% confidence interval [CI] 143.54, 110.95-176.13 vs. 223.54 ng/mL, 161.02-286.06 and in AUCinf 685.55, 534.98-878.50 vs. 933.54 ng·h/mL 735.45-1184.99) compared to premenopausal patients. The carriers of the ABCB1 3435 allele T displayed higher Cmax values of 166.59 (95% CI: 129.44-214.39) compared to the wild type at 147.47 ng/mL (95% CI: 111.91-194.34, p = 0.02). In postmenopausal individuals, the decrease in P-gp activity of ~40% may lead to an increased plasma exposure of orally administered P-gp substrates.

Stereoselective determination of metoprolol and its metabolite α-hydroxymetoprolol in plasma by LC-MS/MS: application to pharmacokinetics during pregnancy.

Metoprolol is available for clinical use as a racemic mixture. The S-(-)-metoprolol enantiomer is the one expressing higher activity in the blockade of the ß(1)-adrenergic receptor. The α-hydroxymetoprolol metabolite also has activity in the blockade of the ß(1)-adrenergic receptor. The present study describes the development and validation of a stereoselective method for sequential analysis of metoprolol and of α-hydroxymetoprolol in plasma using high-performance liquid chromatography with tandem mass spectrometry (LC-MS/MS). 1-ml aliquots of plasma were extracted with dichloromethane : diisopropyl ether (1:1, v/v). Metoprolol enantiomers and α-hydroxymetoprolol isomers were separated on a Chiralpak AD column (Daicel Chemical Industries, New York, NY, USA) and quantitated by LC-MS/MS. The limit of quantitation obtained was 0.2 ng of each metoprolol enantiomer/ml plasma and 0.1 ng/ml of each α-hydroxymetoprolol isomer/ml plasma. The method was applied to the study of kinetic disposition of metoprolol in plasma samples collected up to 24 h after the administration of a single oral dose of 100-mg metoprolol tartrate to a hypertensive parturient with a gestational age of 42 weeks. The clinical study showed that the metoprolol pharmakokinetics is enantioselective, with the observation of higher area under the curve (AUC)(0-∞) values for S-(-)-metoprolol (AUC(S-(-)) /AUC(R-(+)) = 1.81) and the favoring of the formation of the new chiral center 1'R of α-hydroxymetoprolol (AUC(0-∞) (1'R/1'S) = 2.78).

Influence of gasoline inhalation on the enantioselective pharmacokinetics of fluoxetine in rats.

Fluoxetine is used clinically as a racemic mixture of (+)-(S) and (-)-(R) enantiomers for the treatment of depression. CYP2D6 catalyzes the metabolism of both fluoxetine enantiomers. We aimed to evaluate whether exposure to gasoline results in CYP2D inhibition. Male Wistar rats exposed to filtered air (n = 36; control group) or to 600 ppm of gasoline (n = 36) in a nose-only inhalation exposure chamber for 6 weeks (6 h/day, 5 days/week) received a single oral 10-mg/kg dose of racemic fluoxetine. Fluoxetine enantiomers in plasma samples were analyzed by a validated analytical method using LC-MS/MS. The separation of fluoxetine enantiomers was performed in a Chirobiotic V column using as the mobile phase a mixture of ethanol:ammonium acetate 15 mM. Higher plasma concentrations of the (+)-(S)-fluoxetine enantiomer were found in the control group (enantiomeric ratio AUC((+)-(S)/(-)-(R)) = 1.68). In animals exposed to gasoline, we observed an increase in AUC(0-∞) for both enantiomers, with a sharper increase seen for the (-)-(R)-fluoxetine enantiomer (enantiomeric ratio AUC((+)-(S)/(-)-(R)) = 1.07), resulting in a loss of enantioselectivity. Exposure to gasoline was found to result in the loss of enantioselectivity of fluoxetine, with the predominant reduction occurring in the clearance of the (-)-(R)-fluoxetine enantiomer (55% vs. 30%).

Analysis of oxcarbazepine and the 10-hydroxycarbazepine enantiomers in plasma by LC-MS/MS: application in a pharmacokinetic study.

Oxcarbazepine is a second-generation antiepileptic drug indicated as monotherapy or adjunctive therapy in the treatment of partial seizures or generalized tonic-clonic seizures in adults and children. It undergoes rapid presystemic reduction with formation of the active metabolite 10-hydroxycarbazepine (MHD), which has a chiral center at position 10, with the enantiomers (S)-(+)- and R-(-)-MHD showing similar antiepileptic effects. This study presents the development and validation of a method of sequential analysis of oxcarbazepine and MHD enantiomers in plasma using liquid chromatography with tandem mass spectrometry (LC-MS/MS). Aliquots of 100 µL of plasma were extracted with a mixture of methyl tert-butyl ether: dichloromethane (2:1). The separation of oxcarbazepine and the MHD enantiomers was obtained on a chiral phase Chiralcel OD-H column, using a mixture of hexane:ethanol:isopropanol (80:15:5, v/v/v) as mobile phase at a flow rate of 1.3 mL/min with a split ratio of 1:5, and quantification was performed by LC-MS/MS. The limit of quantification was 12.5 ng oxcarbazepine and 31.25 ng of each MHD enantiomer/mL of plasma. The method was applied in the study of kinetic disposition of oxcarbazepine and the MHD enantiomers in the steady state after oral administration of 300 mg/12 h oxcarbazepine in a healthy volunteer. The maximum plasma concentration of oxcarbazepine was 1.2 µg/mL at 0.75 h. The kinetic disposition of MHD is enantioselective, with a higher proportion of the S-(+)-MHD enantiomer compared to R-(-)-MHD and an AUC(0-12) S-(+)/R-(-) ratio of 5.44.