Effect of Interindividual Variability in Metabolic Clearance and Relative Bioavailability on Rifampicin Exposure in Tuberculosis Patients with and without HIV Co-Infection: Does Formulation Quality Matter?

The present study aims to characterise the pharmacokinetics of rifampicin (RIF) in tuberculosis (TB) patients with and without HIV co-infection, considering the formation of 25-O-desacetyl-rifampicin (desRIF). It is hypothesised that the metabolite formation, HIV co-infection and drug formulation may further explain the interindividual variation in the exposure to RIF. Pharmacokinetic, clinical, and demographic data from TB patients with (TB-HIV+ group; n = 18) or without HIV (TB-HIV- group; n = 15) who were receiving RIF as part of a four-drug fixed-dose combination (FDC) regimen (RIF, isoniazid, pyrazinamide, and ethambutol) were analysed, along with the published literature data on the relative bioavailability of different formulations. A population pharmacokinetic model, including the formation of desRIF, was developed and compared to a model based solely on the parent drug. HIV co-infection does not alter the plasma exposure to RIF and the desRIF formation does not contribute to the observed variability in the RIF disposition. The relative bioavailability and RIF plasma exposure were significantly lower than previously reported for the standard regimen with FDC tablets. Furthermore, participants weighting less than 50 kg do not reach the same RIF plasma exposure as compared to those weighting >50 kg. In conclusion, as no covariate was identified other than body weight on CL/F and Vd/F, low systemic exposure to RIF is likely to be caused by the low bioavailability of the formulation.

In Vivo Activity of Intestinal P-Glycoprotein and Hepatic Organic Anion Transporters Polypeptide in Pregnancy and Postpartum.

This study investigates the influence of pregnancy on the in vivo activity of the intestinal P-glycoprotein (P-gp) and hepatic organic anion transporters polypeptide (OATP/BCRP) using, respectively, fexofenadine and rosuvastatin as probe drugs. Eleven healthy participants were investigated during the third trimester of pregnancy (Phase 1, 28 to 38 weeks of gestation) and in the postpartum period (Phase 2, 8 to 12 weeks postpartum). In both phases, after administration of a single oral dose of fexofenadine (60 mg) and rosuvastatin (5 mg), serial blood samples were collected for up to 24 h. Rosuvastatin and fexofenadine in plasma were analyzed by LC-MS/MS using previously validated methods. The pharmacokinetic parameters of fexofenadine and rosuvastatin (Phoenix WinNonLin software) with normal distribution (Shapiro-Wilk test) are presented as geometric mean and 90% confidence interval. Phases 1 and 2 were compared using the t test (P < .05). Fexofexadine AUC0-24 values do not differ (P-value: .0715) between Phase 1 (641.9 ng h/mL [500.6-823.1]) and Phase 2 (823.8 ng h/mL [641.5-1057.6]) showing that pregnancy (third trimester) does not alter intestinal P-gp activity. However, rosuvastatin AUC0-24 values are higher (P-value: .00005) in Phase 1 (18.7 ng h/mL [13.3-26.4]) when compared to Phase 2 (9.5 ng h/mL [6.7-13.4]), suggesting inhibition of OATP1B1/OATP1B3 transporters. In conclusion, pregnancy assessed during the third trimester does not alter the intestinal P-gp activity but reduces the activity of hepatic OATP1B1/OATP1B3 transporters. Therefore, adjustments in dosage regimens may be necessary for drugs with low therapeutic index, substrates of the OATP1B1/OATP1B3 transporters, administered during the third trimester of pregnancy.

Liver Fibrosis Stages Affect Organic Cation Transporter 1/2 Activities in Hepatitis C Virus-Infected Patients.

This study aims to evaluate the impact of liver fibrosis stages of chronic infection with hepatitis C virus (HCV) on the in vivo activity of organic cation transporters (hepatic OCT1 and renal OCT2) using metformin (MET) as a probe drug. Participants allocated in Group 1 (n = 15, mild to moderate liver fibrosis) or 2 (n = 13, advanced liver fibrosis and cirrhosis) received a single MET 50 mg oral dose before direct-acting antiviral (DAA) drug treatment (Phase 1) and 30 days after achieving sustained virologic response (Phase 2). OCT1/2 activity (MET AUC0-24) was found to be reduced by 25% when comparing the two groups in Phase 2 (ratio 0.75 (0.61-0.93), p < 0.05) but not in Phase 1 (ratio 0.81 (0.66-0.98), p > 0.05). When Phases 1 and 2 were compared, no changes were detected in both Groups 1 (ratio 1.10 (0.97-1.24), p > 0.05) and 2 (ratio 1.03 (0.94-1.12), p > 0.05). So, this study shows a reduction of approximately 25% in the in vivo activity of OCT1/2 in participants with advanced liver fibrosis and cirrhosis after achieving sustained virologic response and highlights that OCT1/2 in vivo activity depends on the liver fibrosis stage of chronic HCV infection.

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.

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.

The Impact of Inflammation on the In Vivo Activity of the Renal Transporters OAT1/3 in Pregnant Women Diagnosed with Acute Pyelonephritis.

Inflammation can regulate hepatic drug metabolism enzymes and transporters. The impact of inflammation on renal drug transporters remains to be elucidated. We aimed to quantify the effect of inflammation (caused by acute pyelonephritis) on the in vivo activity of renal OAT1/3, using the probe drug furosemide. Pregnant women (second or third trimester) received a single oral dose of furosemide 40 mg during acute pyelonephritis (Phase 1; n = 7) and after its resolution (Phase 2; n = 7; by treatment with intravenous cefuroxime 750 mg TID for 3-7 days), separated by 10 to 14 days. The IL-6, IFN-γ, TNF-α, MCP-1, and C-reactive protein plasma concentrations were higher in Phase I vs. Phase II. The pregnant women had a lower geometric mean [CV%] furosemide CLsecretion (3.9 [43.4] vs. 6.7 [43.8] L/h) and formation clearance to the glucuronide (1.1 [85.9] vs. 2.3 [64.1] L/h) in Phase 1 vs. Phase 2. Inflammation reduced the in vivo activity of renal OAT1/3 (mediating furosemide CLsecretion) and UGT1A9/1A1 (mediating the formation of furosemide glucuronide) by approximately 40% and 54%, respectively, presumably by elevating the plasma cytokine concentrations. The dosing regimens of narrow therapeutic window OAT drug substrates may need to be adjusted during inflammatory conditions.

Determination of furosemide and its glucuronide metabolite in plasma, plasma ultrafiltrate and urine by HPLC-MS/MS with application to secretion and metabolite formation clearances in non-pregnant and pregnant women.

Furosemide (FUR) has been used in probe drugs cocktails for in vivo evaluation of the renal transporters OAT1 and OAT3 activities in studies of drug-drug interactions (generally using probenecid as an inhibitor) and drug-disease interactions. The objective of this study was to develop and validate methods for FUR and its glucuronide metabolite (FUR-GLU) analysis in plasma, plasma ultrafiltrate and urine for application in pharmacokinetics studies: a pilot drug-drug interaction study in pregnant women (n = 2), who received a single oral dose of FUR (40 mg) and in another occasion a single oral dose of probenecid (750 mg) before a single oral dose of FUR (40 mg), and in non-pregnant women participants (n = 12), who only received a single oral dose of FUR (40 mg). The samples preparation for FUR in 50 µL of plasma and plasma lysate were carried by acidified liquid-liquid extraction, while 50 µL of urine and 200 µL of plasma ultrafiltrate were simply diluted with the mobile phase. The methods presented linearities in the range of 0.50 - 2500 ng/mL of plasma and plasma lysate, 0.125 - 250 ng/mL of plasma ultrafiltrate, and 50 - 20,000 ng/mL of urine. FUR-GLU methods presented linearities in the range of 0.125 - 250 ng/mL of plasma ultrafiltrate and 50 - 20,000 ng/mL of urine. Precision and accuracy evaluations showed coefficients of variation and relative errors < 15%. In the pregnant women participants, the mean values of FUR CLrenal, CLsecretion, CLformation. FUR-GLU and CLnon-renal were all reduced when probenecid was administered with FUR (8.24 vs 2.89 L/h, 8.15 vs 2.80 L/h, 3.86 vs 1.75 L/h, 48.26 vs 22.10 L/h, respectively). Non-pregnant women presented similar values of FUR CLrenal, CLsecretion, CLformation. FUR-GLU to the pregnant women who received FUR only. Finally, FUR fraction unbound (fu) resulted in values of approximately 1% in pregnant women and to 0.22% in non-pregnant women. These developed and validated methods for FUR and FUR-GLU quantification in multiple matrices can allow the further investigation of UGT1A9/1A1 and the fu when FUR is administered as an OAT 1 and 3 in vivo probe.

Total, Unbound, Renal, and Hepatic Clearances of Raltegravir and the Formation and Elimination Clearances of Raltegravir Glucuronide in Pregnant Women.

This work aimed to evaluate the total, unbound, renal, and hepatic clearances of raltegravir (RAL) and the formation and elimination clearances of raltegravir glucuronide (RAL GLU) in pregnant women living with HIV. The participants received RAL 400 mg twice daily during the third trimester (n = 15) of gestation, delivery (n = 15), and the postpartum period (n = 8). Pharmacokinetic parameter values were calculated on the basis of plasma and urine data using noncompartmental methods. RAL clearances for the third trimester of gestation were as follows: total clearance: geometric mean, 63.63 L/h (95% CI, 47.5-85.25); renal clearance: geometric mean, 2.56 L/h (95% CI, 1.96-3.34); hepatic clearance: geometric mean, 60.52 L/h (95% CI, 44.65-82.04); and unbound clearance: geometric mean, 281.14 L/h (95% CI, 203.68-388.05). RAL GLU formation and elimination clearances for the third trimester of gestation were 7.57 L/h (95% CI, 4.94-11.6) and 8.71 L/h (95% CI, 6.71-11.32), respectively. No differences were observed in RAL GLU pharmacokinetic parameters between the third trimester of gestation and the postpartum period, except for higher formation (7.57 vs 4.03 L/h) and elimination (8.71 vs 4.92 L/h) clearances during the third trimester. The findings based on plasma and urine data are consistent with an increase in the hepatic uridine 5' diphospho-glucuronosyltransferase isoenzymes activities involved in RAL metabolism during pregnancy, and the formation of RAL GLU is a minor route of RAL elimination. Compared to the postpartum period, in the third trimester of gestation, the similar RAL plasma exposure in pregnant women reinforces the maintenance of an RAL regimen including a 400-mg oral dose twice daily during pregnancy.

Effect of Chronic Hepatitis C on the Activity of the Membrane Transporters P-gp and OATP1B1/BCRP on Patients With Different Stages of Hepatic Fibrosis.

The activity of the membrane transporters organic anion-transporting polypeptide 1B1 (OATP1B1) & breast cancer resistance protein (BCRP) (rosuvastatin) and P-glycoprotein (P-gp) (fexofenadine) was evaluated in patients with chronic hepatitis C virus (HCV) infection (n = 28), genotypes 1 and 3, investigated before the treatment with direct-acting antiviral agents (Phase 1) and up to 30 days after the assessment of the virologic response (Phase 2). Participants allocated in Groups 1 (n = 15; F0/F1 and F2, mild to moderate liver fibrosis) and 2 (n = 13; F3 and F4, advanced course of liver fibrosis/cirrhosis) received in both phases fexofenadine (10 mg) and rosuvastatin (2 mg). OATP1B1 & BCRP activity (rosuvastatin area under the plasma concentration-time curve of rosuvastatin from time zero to infinity (AUC0-∞ )) was reduced in Groups 1 and 2, respectively, by 25% (ratio 0.75 (0.53-0.82), P < 0.01) and 31% (ratio 0.69 (0.46-0.85), P < 0.05) in Phase 1 compared with Phase 2. OATP1B1 & BCRP activity was reduced in Phases 1 and 2, respectively, by 49% (median ratio 1.51 (1.17-2.20), P < 0.05) and 61% (ratio 1.39 (1.16-2.02), P < 0.01) in Group 2 compared with Group 1. P-gp activity (fexofenadine AUC0-∞ ) was also reduced in Phase 1 compared with Phase 2 (ratio Phase2/Phase1 0.79 (0.66-0.96) in Group 1 and 0.81 (0.69-0.96) in Group 2) as well as in Group 2 compared with Group 1 in both Phases (ratio Group2/Group1 1.47 (1.08-2.01) in Phase 1 and 1.51 (1.10-2.07) in Phase 2). Thus, clinicians administering OATP1B1 & BCRP and P-gp substrates with low therapeutic indexes should consider the evolution of the treatment and the stage of HCV infection.

Pharmacodynamic effect of gabapentin on central nervous system in patients with chronic low back pain: a [99mTc]Tc-ECD SPECT study.

BACKGROUND: Gabapentin is an effective therapeutic alternative for chronic low back pain, indicated in several guidelines for treating neuropathic pain as first-line medication. This study aimed to describe the pharmacodynamics of gabapentin in the central nervous system of patients with chronic low back pain (CLBP) by using single-photon emission CT (SPECT) with [99mTc]Tc-ECD. METHODS: We selected 13 patients with CLBP due to lumbar disc herniation. They underwent SPECT before and after using gabapentin, compared with a SPECT database of healthy volunteers. A second analysis compared regional cerebral blood flow (rCBF) changes between responders and non-responders to gabapentin and the healthy controls. RESULTS: The mean age of patients was 41 years, and the mean pain intensity was 5.92 points, measured by the Numeric Rating Scale. After using gabapentin, SPECT showed an increase of rCBF in the bilateral anterior cingulate gyrus and a decrease of rCBF in periaqueductal gray matter. Non-responder patients with gabapentin showed a post-treatment decrease of rCBF in the paracentral lobule of the brain. CONCLUSIONS: A lack of improvement in some patients with gabapentin may be associated with an activated affective circuit of pain, evidenced by the increase of rCBF of the anterior cingulate cortex. A maladaptive brain state in chronic pain can explain the decrease of rCBF in the default mode network structures. Gabapentin acts directly or indirectly on neurons of periaqueductal gray substance by increasing the pain threshold and decreasing the rCBF of this structure.

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.

P-Glycoprotein and Organic Anion Transporter Polypeptide 1B/Breast Cancer Resistance Protein Drug Transporter Activity in Pregnant Women Living With HIV.

This study evaluates the influence of pregnancy and HIV infection in conjunction with the use of raltegravir, lamivudine, and tenofovir disoproxil fumarate (combined antiretroviral therapy [cART]) on intestinal P-glycoprotein (P-gp) and hepatic organic anion transporter polypeptide (OATP) 1B1/1B3 and/or breast cancer resistance protein (BCRP) drug transporter activity using rosuvastatin (OATP1B/BCRP) and fexofenadine (P-gp) probes. Single oral doses of 5-mg rosuvastatin and 60-mg fexofenadine were administered to women living with HIV under cART in the third trimester of gestation (n = 15) and postpartum period (n = 10). A control group of 12 healthy nonpregnant women also was investigated. Pharmacokinetic parameters were estimated by using a noncompartmental method and evaluated by t test (P < .05). The rosuvastatin area under the plasma concentration-time curve from time 0 to the last quantifiable concentration (AUC0-last ) value was higher in the third trimester of pregnancy (19.5 [95%CI, 16.8-22.3] ng • h/mL] when compared to postpartum (13.3 [95%CI, 9.3-17.5] ng • h/mL), while the fexofenadine AUC0-last values did not differ between the third trimester of pregnancy (738.0 [95%CI, 611.4-864.6] ng • h/mL) and postpartum period (874.9 [95%CI, 408.2-1342.0] ng• h/mL). The rosuvastatin AUC0-last values did not differ between healthy nonpregnant women (13.8 [95%CI, 10.0-17.6] ng • h/mL) and women living with HIV in the postpartum period (13.3 [95%CI, 9.3-17.5] ng • h/mL), and the fexofenadine AUC0-last values did not differ between the 2 investigated groups (603.6 [95%CI, 467.5-739.7] ng • h/mL vs 874.9 [95%CI, 408.2-1342.0] ng • h/mL). It is suggested that gestation inhibits the hepatic OATP1B1/1B3 and/or BCRP activity but does not alter intestinal P-gp activity. The influence of HIV infection in conjunction with use of cART on OATP1B/BCRP and intestinal P-gp activity was not observed.

HPLC-MS/MS method for determination of betamethasone in human plasma with application to a dichorionic twin pregnancy pharmacokinetic and placental transfers studies

Abstract Betamethasone (BET) is a synthetic glucocorticoid recommended for pregnant women at imminent risk of preterm birth before 34 weeks to reduce neonatal complications. There are different techniques to describe BET plasma quantification. However, none quantified the plasmatic concentration of BET in dichorionic (DC) twin pregnancies using LC-MS. Our objectives were to develop and validate a method for quantifying BET by LC-MS for pharmacokinetic (PK) and placental transfer studies in DC twin pregnancies. Blood samples were collected after intramuscular administration of a single BET dose containing 6 mg disodium phosphate + 6 mg acetate. BET was determined in plasma by liquid-liquid extraction. The method showed linearity in the range of 2-250 ng/mL, as well as precision and accuracy with a coefficient of variation and relative standard errors ≤ 15%. Additionally, the method presented selectivity and did not present matrix or carry-over effect. Stability tests also presented coefficient of variation and relative standard errors ≤ 15%. This is the first study which describe maternal and fetal plasma concentrations of BET in a DC twin pregnancy. The BET PK parameters were AUC0-∞, CL/F, Vd/F, Cmax, Tmax of 292.20 h*ng/mL, 39.08 L/h, 278.72 L, 25.55 ng/mL and 0.58 h, respectively. The placental transfer ratios of umbilical vein/maternal vein and intervillous space/maternal vein were 0.14 and 0.19 and 0.40 and 0.27 for both twins, respectively. However, a clinical study with more subjects is imperative to confirm this higher concentration of BET in the intervillous space

Neurobiological substrates of chronic low back pain (CLBP): a brain [99mTc]Tc-ECD SPECT study.

BACKGROUND: Recent neuroimaging studies have demonstrated pathological mechanisms related to cerebral neuroplasticity in chronic low back pain (CLBP). Few studies have compared cerebral changes between patients with and without pain in the absence of an experimentally induced stimulus. We investigated the neurobiological substrates associated with chronic low back pain using [99mTc]Tc-ECD brain SPECT and correlated rCBF findings with the numeric rating scale (NRS) of pain and douleur neuropathique en 4 questions (DN4). Ten healthy control volunteers and fourteen patients with neuropathic CLBP due to lumbar disc herniation underwent cerebral SPECT scans. A quantitative comparison of rCBF findings between patients and controls was made using the Statistical Parametric Mapping (SPM), revealing clusters of voxels with a significant increase or decrease in rCBF. The intensity of CLBP was assessed by NRS and by DN4. RESULTS: The results demonstrated an rCBF increase in clusters A (occipital and posterior cingulate cortex) and B (right frontal) and a decrease in cluster C (superior parietal lobe and middle cingulate cortex). NRS scores were inversely and moderately correlated with the intensity of rCBF increase in cluster B, but not to rCBF changes in clusters A and C. DN4 scores did not correlate with rCBF changes in all three clusters. CONCLUSIONS: This study will be important for future therapeutic studies that aim to validate the association of rCBF findings with the pharmacokinetic and pharmacodynamic profiles of therapeutic challenges in pain.

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.

No implication of HIV coinfection on the plasma exposure to rifampicin, pyrazinamide, and ethambutol in tuberculosis patients.

There are contrasting findings regarding the effect of HIV on the pharmacokinetics of first-line anti-tubercular drugs (FLATDs) due to a lack of prospective controlled clinical studies, including patients with tuberculosis (TB) and patients with TB living with HIV. This study aims to assess the effect of HIV coinfection and antiviral therapy on the plasma exposure to FLATDs in patients with TB. HIV negative (TB-HIV- group; n = 15) and HIV positive (TB-HIV+ group; n = 18) adult patients with TB were enrolled during the second month of FLATDs treatment. All TB-HIV+ patients were on treatment with lamivudine, tenofovir (or zidovudine), and raltegravir (or efavirenz). Serial blood sampling was collected over 24 h and FLATDs pharmacokinetic parameters were evaluated using noncompartmental methods. In the TB-HIV+ patients, dose-normalized plasma exposure area under the curve from zero to 24 h (nAUC0-24 ; geometric mean and 95% confidence interval [CI]) values at steady-state to rifampicin, pyrazinamide, and ethambutol were 18.38 (95% CI 13.74-24.59), 238.21 (95% CI 191.09-296.95), and 18.33 (95% CI 14.56-23.09) µg∙h/ml, respectively. Similar plasma exposure was found in the TB-HIV- patients. The geometric mean and 90% CI of the ratios between TB-HIV- and TB-HIV+ groups suggest no significant pharmacokinetic interaction between the selected antivirals and FLATDs. Likewise, HIV coinfection itself does not appear to have any effect on the plasma exposure to FLATDs.

Sensitive LC-MS/MS Methods for Amphotericin B Analysis in Cerebrospinal Fluid, Plasma, Plasma Ultrafiltrate, and Urine: Application to Clinical Pharmacokinetics.

Neurocryptococcosis, a meningoencephalitis caused by Cryptococcus spp, is treated with amphotericin B (AmB) combined with fluconazole. The integrity of the brain-blood barrier and the composition of the cerebrospinal fluid (CSF) may change due to infectious and/or inflammatory diseases such as neurocryptococcosis allowing for the penetration of AmB into the central nervous system. The present study aimed to develop LC-MS/MS methods capable of quantifying AmB in CSF at any given time of the treatment in addition to plasma, plasma ultrafiltrate, with sensitivity compatible with the low concentrations of AmB reported in the CSF. The methods were successfully validated in the four matrices (25 µl, 5-1,000 ng ml-1 for plasma or urine; 100 µl, 0.625-250 ng ml-1 for plasma ultrafiltrate; 100 µl, 0.1-250 ng ml-1 for CSF) using protein precipitation. The methods were applied to investigate the pharmacokinetics of AmB following infusions of 100 mg every 24 h for 16 days administered as a lipid complex throughout the treatment of a neurocryptococcosis male patient. The methods allowed for a detailed description of the pharmacokinetic parameters in the assessed patient in the beginning (4th day) and end of the treatment with AmB (16th day), with total clearances of 7.21 and 4.25 L h-1, hepatic clearances of 7.15 and 4.22 L h-1, volumes of distribution of 302.94 and 206.89 L, and unbound fractions in plasma ranging from 2.26 to 3.25%. AmB was quantified in two CSF samples collected throughout the treatment with concentrations of 12.26 and 18.45 ng ml-1 on the 8th and 15th days of the treatment, respectively. The total concentration of AmB in plasma was 31 and 20 times higher than in CSF. The unbound concentration in plasma accounted for 77 and 44% of the respective concentrations in CSF. In conclusion, the present study described the most complete and sensitive method for AmB analysis in plasma, plasma ultrafiltrate, urine, and CSF applied to a clinical pharmacokinetic study following the administration of the drug as a lipid complex in one patient with neurocryptococcosis. The method can be applied to investigate the pharmacokinetics of AmB in CSF at any given time of the treatment.

Determination of misoprostol acid in plasma samples by UPLC-MS/MS with application in a maternal-fetal pharmacokinetic study following a low misoprostol dose vaginally to induce labor.

Misoprostol is a prostaglandin E1 synthetic analogous used for elective interruptions of early pregnancy, treatment of incomplete abortion, postpartum hemorrhage and induction of full-term labor. Its a lipophilic drug, passing by extensive and rapid pre-systemic metabolism into the active metabolite, misoprostol acid (MA). The objective of this study was to develop and validate a highly sensitive method for MA determination in plasma using UPLC-MSMS, with application in a study of maternal-fetal pharmacokinetics in healthy parturients women (n = 10) after administration of 25 µg misoprostol vaginally. The method presented linearity of 2-10 pg/mL and acceptable precision, accuracy, plasma and solution stability. The parturients women presented median (interquartile range) values of AUC0-6 of 68.0 (40.8-84.7) pg.h/mL, Cmax of 21.9 (11.9-30.1) pg/mL and Tmax of 2.25 (0.69-5.00) h. The placental transfer of MA was assessed from the umbilical vein/maternal blood ratios of 1.40 (0.91-2.13) and intervillous space/maternal blood ratios of 0.49 (0.15-3.41). In conclusion, this method presented high sensitivity, being able to quantify MA in plasma samples following a low 25 µg misoprostol administered vaginally aimed to induce labor in parturients women. Additionally, this is the first description of the placental transfer of MA after a vaginal administration of misoprostol.

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.