Prediction of the Area under the Curve Using Limited-Point Blood Sampling in a Cocktail Study to Assess Multiple CYP Activities.

A cocktail study is an in vivo evaluation method to assess multiple CYP activities via a single trial and single administration of a cocktail drug that is a combination of multiple CYP substrates. However, multiple blood samples are required to evaluate the pharmacokinetics of a CYP probe drug. A limited-point sampling method is generally beneficial in clinical studies because of the simplified protocol and reduced participant burden. The aim of this study was to evaluate whether a limited-point plasma concentration analysis of CYP substrates in a cocktail drug could predict their area under the curve (AUC). We created prediction models of five CYP substrates (caffeine, losartan, omeprazole, dextromethorphan, and midazolam) using multiple linear regressions from the data of two cocktail studies, and then performed predictability analysis of these models using data derived from data in the co-administration with inducer (rifampicin) and inhibitors (fluvoxamine and cimetidine). For the administration of inhibitors, the AUC prediction accuracy (mean absolute error (MAE)) were <39.5% in Model 1 and <26.2% in Model 2 which were created using 1- and 4-point sampling data. MAE shows larger values in the administration of inducer in compared with the administration of inhibitors. The accuracy of the prediction in Model 2 could be acceptable for screening of inhibitions. MAE for caffeine, dextromethorphan, and midazolam were acceptable in the model that used 4 sampling points from all data. The use of this method could reduce the burden on the subject and make it possible to evaluate each AUC in a minimally invasive manner.

Quantification of serum levels in mice of seven drugs (and six metabolites) commonly taken by older people with polypharmacy.

Polypharmacy (use of ≥ 5 drugs) is common in older people but has minimal preclinical or clinical evidence of safety or efficacy and is associated with adverse outcomes in older people. Drug-drug interactions are poorly understood beyond drug pairs. An efficient and sensitive method to measure multiple serum drugs and metabolites could inform drug dosing in polypharmacy. Development of a sensitive liquid chromatography - tandem mass spectrometry method to simultaneously measure seven drugs and their respective metabolites in serum in a preclinical model of polypharmacy. This method was validated for optimal recovery, matrix effect, limit of quantification (LOQ), inter- and intra-day variability, and carry over. Serum samples from mice (n = 5-6/group) treated with chronic oral doses of three polypharmacy regimens and five monotherapies were screened for drug and metabolite levels (metoprolol, α-hydroxymetoprolol, O-desmethylmetoprolol, omeprazole, 5-hydroxyomeprazole, omeprazole sulphone, acetaminophen, irbesartan, citalopram, oxybutynin, oxycodone, noroxycodone, oxymorphone and tenivastatin). The LOQ for the compounds ranged from 0.05 to 0.1 ng/mL in serum. Recovery, matrix effect, and inter- and intra-day variability peak response were acceptable. No carry over was observed at the concentrations tested. Analytes were detectable in mice treated with these drugs, and differences in drug levels were observed with different polypharmacy and monotherapy regimens. The method is sensitive and robust to measure parent drugs and metabolites simultaneously in the context of polypharmacy. Polypharmacy appeared to affect drug levels in a preclinical model. This model can be used to understand pharmacokinetics of chronic polypharmacy, which could inform prescribing and improve outcomes for older people.

Effect of food on the pharmacokinetics of omeprazole, pantoprazole and rabeprazole.

BACKGROUND: The pharmacokinetics of proton pump inhibitors (PPIs) may be affected by food intake. We aimed to evaluate the effect of food on the pharmacokinetics of omeprazole, rabeprazole, and pantoprazole. SETTING: The study population comprised 186 healthy volunteers participating in 6 bioequivalence clinical trials. METHOD: Subjects were evaluated to determine the effect of a high-fat breakfast on the pharmacokinetics of omeprazole (n = 36), rabeprazole (n = 69), and pantoprazole (n = 81). MAIN OUTCOME MEASURE: Drug plasma concentrations were measured using high-performance liquid chromatography coupled to mass spectrometry. RESULTS: Food affected the pharmacokinetics of omeprazole (increased Tmax and decreased AUC and Cmax), pantoprazole (increased Tmax and decreased AUC), and rabeprazole (increased Tmax, Cmax and half-life). Food increased variability in Tmax for all 3 drugs, delaying absorption around 3 to 4 h and until 20 h in some subjects. CONCLUSION: As food delays the absorption of PPIs and increases their variability, it would be better to administer these drugs under fasting conditions. TRIAL REGISTRATION: European Union Drug Regulating Authorities Clinical Trials Database: EudraCT : 2004-003863-59 (registration date 05/MAR/2004), EudraCT 2006-001162-17 (registration date 17-MAR-2006), EudraCT: 2007-002489-37 (registration date 12-JUN-2007), EudraCT: 2007-002490-31 (registration date 12-JUN-2007), EudraCT: 2010-024029-19 (registration date 23-NOV-2010).

Simultaneous enantioselective determination of omeprazole, rabeprazole, lansoprazole, and pantoprazole enantiomers in human plasma by chiral liquid chromatography-tandem mass spectrometry.

Proton pump inhibitors, including omeprazole, rabeprazole, lansoprazole, and pantoprazole, achieved simultaneous enantioselective determination in the human plasma by chiral liquid chromatography-tandem mass spectrometry. The four corresponding stable isotope-labeled proton pump inhibitors were adopted as the internal standards. Each enantiomer and the internal standards were extracted with acetonitrile containing 0.1% ammonia, then separated with a Chiralpak IC column (5 µm, 4.6 mm × 150 mm) within 10 min. The mobile phase was composed of acetonitrile-ammonium acetate (10 mM) containing 0.2% acetic acid (50:50, v/v). To quantify all enantiomers, an API 4000 tandem mass spectrometer was used, and multiple reaction monitoring transitions were performed on m/z 360.1→242.1, 384.1→200.1, 370.1→252.1, and 346.1→198.1, respectively. No significant matrix effect was observed for all analytes. The calibration curve for all enantiomers were linear from 1.25 to 2500 ng/mL. The precisions for intra- and inter-run were < 14.2%, and the accuracy fell in the interval of -5.3 to 8.1%. Stability of samples was confirmed under the storage and processing conditions. The developed method was also suitable for separation and determination of ilaprazole enantiomers. The validated method combining the equilibrium dialysis method was applied to the protein binding ratio studies of four pairs proton pump inhibitor enantiomers in human plasma.

Assessment of effects of repeated oral doses of fedratinib on inhibition of cytochrome P450 activities in patients with solid tumors using a cocktail approach.

PURPOSE: Fedratinib, an oral selective kinase inhibitor with activity against both wild type and mutationally activated Janus kinase 2, has been approved for the treatment of adult patients with intermediate-2 or high-risk myelofibrosis by the US Food and Drug Administration. In vitro studies indicated that fedratinib was an inhibitor of several cytochrome P450 (CYP) enzymes. The primary objective of this study was to evaluate the effects of repeated doses of fedratinib on the activity of CYP2D6, CYP2C19, and CYP3A4 in patients with solid tumors using a CYP probe cocktail. METHODS: An open-label, one-sequence, two-period, two-treatment crossover study was conducted. Patients were administered a single oral dose cocktail of metoprolol (100 mg), omeprazole (20 mg), and midazolam (2 mg) used as probe substrates for CYP2D6, CYP2C19, and CYP3A4 enzyme activities, respectively, without fedratinib on Day -1 or with fedratinib on Day 15. RESULTS: Coadministration of 500 mg once-daily doses of fedratinib for 15 days increased the mean area under the plasma concentration-time curve from time zero to infinity following a single-dose cocktail containing metoprolol (CYP2D6 substrate), omeprazole (CYP2C19 substrate), and midazolam (CYP3A4 substrate) by 1.77-fold (90% confidence interval [CI] 1.27-2.47) for metoprolol, 2.82-fold (90% CI 2.26-3.53) for omeprazole, and 3.84-fold (90% CI 2.62-5.63) for midazolam, respectively. The mean plasma Day 14/Day 1 ratio of 4ß-hydroxycholesterol, an endogenous biomarker of CYP3A4 activity, was 0.59 (90% CI 0.54-0.66), suggesting a net inhibition of CYP3A4 by fedratinib. CONCLUSION: Fedratinib is a weak inhibitor of CYP2D6, and a moderate inhibitor of CYP2C19 and CYP3A4. These results serve as the basis for dose modifications of these CYP substrate drugs when co-administered with fedratinib.

Has the Time Come to Employ Population and Individual Bioequivalence for the Evaluation of Generics?

BACKGROUND: Bioequivalence studies are a vital part of drug development. The average bioequivalence approach is the standard method of assessment to conclude whether the generic product is bioequivalent to the innovator product. Of late, debates are on whether the average bioequivalence approach adequately addresses drug interchangeability as it considers only population mean for the evaluation especially when highly variable drug products and narrow therapeutic index drugs are dealt with. Hence, the alternative approaches like population bioequivalence and individual bioequivalence assessment approaches emerge as they consider inter/intra-subject variance and subject- by-formulation variance along with population mean. OBJECTIVES: The objective of the study was to apply different bioequivalence assessment approaches in a replicate bioequivalence study to evaluate the drug interchangeability. METHODS: This was an open-label, single-dose, randomized, balanced, two-treatment, three-period, three-sequence, partial replicate crossover bioequivalence study of omeprazole enteric-coated tablet 20 mg conducted on 48 normal healthy subjects under fed conditions. The plasma concentration of omeprazole was analyzed by a validated bioanalytical method to determine the pharmacokinetic and statistical parameters to assess average bioequivalence, population bioequivalence, and individual bioequivalence. RESULTS: In this study, test formulation was shown to be bio-inequivalent to the reference formulation by average bioequivalence, population bioequivalence, and individual bioequivalence approaches. CONCLUSION: The outcome of the evaluation clearly states that the bioequivalence outcome of all these approaches are the same. Obviously, it does not mean that these three approaches provide the same outcome though the consideration of variances varies. Certainly, population bioequivalence and individual bioequivalence approach will be more accurate for the assessment of drug interchangeability.

Recent insight on improving the iron chelation efficacy of deferasirox by adjuvant therapy in transfusion dependent beta thalassemia children with sluggish response.

Background: Deferasirox is the first line of treatment in iron overload. In spite of the many studies concerning the efficacy of deferasirox, some patients remain unresponsive to deferasirox.Methods: One hundred and sixty patients were enrolled in stratified-randomized controlled study. Patients were randomly divided into four regimens, group I (n = 40) received 30 mg/kg deferasirox, group II (n = 40) received 20 mg omeprazole and 30 mg/kg deferasirox, group III (n = 40) received 400 mg vitamin E and 30 mg/kg deferasirox and group IV (n = 40) received 420 mg silymarin and 30 mg/kg deferasirox. Blood specimens were collected from each patient for up to 24 h, and then plasma deferasirox concentrations were inspected.Results: Silymarin, Vitamin E, and omeprazole significantly increased the peak plasma concentration of deferasirox (P < 0.001) by 27.9, 14.9 and 2.4 fold, respectively, as compared to deferasirox alone. The bioavailability of deferasirox was improved up to 3.03, 3.57, and 4.98-fold, respectively, following administration of omeprazole, vitamin E, and silymarin compared to deferasirox alone.Conclusion: Silymarin, vitamin E, and omeprazole represent promising adjuvant therapy to improve the chelation efficacy of deferasirox that might also be further applied to enhance the pharmacokinetics of deferasirox to overcome the lack of response.

HPLC Determination of Imidazoles with Variant Anti-Infective Activity in Their Dosage Forms and Human Plasma.

A suitable HPLC method has been selected and validated for rapid simultaneous separation and determination of four imidazole anti-infective drugs, secnidazole, omeprazole, albendazole, and fenbendazole, in their final dosage forms, in addition to human plasma within 5 min. The method suitability was derived from the superiority of using the environmentally benign solvent, methanol over acetonitrile as a mobile phase component in respect of safety issues and migration times. Separation of the four anti-infective drugs was performed on a Thermo Scientific® BDS Hypersil C8 column (5 µm, 2.50 × 4.60 mm) using a mobile phase consist of MeOH: 0.025 M KH2PO4 (70:30, v/v) adjusted to pH 3.20 with ortho-phosphoric acid at room temperature. The flow rate was 1.00 mL/min and maximum absorption was measured with UV detector set at 300 nm. Limits of detection were reported to be 0.41, 0.13, 0.18, and 0.15 µg/mL for secnidazole, omeprazole, albendazole, and fenbendazole, respectively, showing a high degree of the method sensitivity. The method of analysis was validated according to Food and Drug Administration (FDA)guidelines for the determination of the drugs, either in their dosage forms with highly precise recoveries, or clinically in human plasma, especially regarding pharmacokinetic and bioequivalence studies.

[Effect of omeprazole on plasma concentration and adverse reactions of capecitabine in patients with colon cancer].

Objective: To investigate the effect of omeprazole on plasma concentration, efficacy and adverse reactions of capecitabine in patients with colon cancer. Methods: Seventy-two patients with colon cancer treated with capecitabine were analysed retrospective. The patients treated with capecitabine combined with omeprazole were identified as experimental group and the capecitabine treatment alone as control group.The differences of blood concentration and the side effects of capecitabine between these two groups were compared. Results: The plasma concentration of 5-Fluorouracilum in experimental group was (126.25±50.59) µg/ml, without significant difference of (123.09±56.70) µg/ml in control group (P=0.121). The incidence of Ⅲ to Ⅳ degree bone marrow suppression, nausea, vomiting, diarrhea and hand-foot syndrome in experimental group were 13.8%, 0%, 0% and 19.4%, respectively. In control group, the incidence of Ⅲ to Ⅳ degree bone marrow suppression, nausea, vomiting, diarrhea and the hand-foot syndrome were 11.1%, 0%, 0% and 19.4%, respectively, without significant difference of experimental group (P>0.05). The incidence of acid reflux and heartburn in the control group was 72.2%, significantly higher than 44.4% of the experimental group (P<0.05). The objective response rate (ORR) and progression-free survival time (PFS) in these two groups were 30.6% and 33.3%, and 8.0 month and 8.5 month, respectively, without significant difference (P>0.05). Conclusion: The intravenous omeprazole attenuates reflux and heartburn of colon cancer patients treated with capecitabine, without affecting its plasma concentration and side effects and has no impact on the PFS of these patients.

Intestine-targeted delivery potency of O-carboxymethyl chitosan-coated layer-by-layer microcapsules: An in vitro and in vivo evaluation.

The intestine-targeted delivery performance of the gum Arabic (GA) - O-carboxymethyl chitosan (OCMC) microcapsules prepared by layer-by-layer (LbL) assembly and genipin crosslinking was evaluated by using an acid-susceptible compound omeprazole as the model. Confocal laser scanning microscope observation revealed that spherical microcapsules with the core-shell structure were successful fabricated. Genipin crosslinking did not affect the microencapsulation yield or drug load, but significantly decreased the particle size and positive charge of the microcapsules, and increased their stability against disintegration in the simulated gastric fluid. Pharmacokinetic analysis indicated that entrapment by GA - OCMC LbL assembly greatly improved the bioavailability of omeprazole and crosslinking by 0.1 mg/mL genipin led to the highest value of 8.76 relative to the control formulation. It was concluded that the GA - OCMC LbL microcapsules could be used for the oral delivery of nutraceuticals and its delivery performance could be tailored by varying the genipin crosslinking degree.

Evaluation of potential herbal-drug interactions of a standardized propolis extract (EPP-AF®) using an in vivo cocktail approach.

ETHNOPHARMACOLOGICAL RELEVANCE: Propolis has been employed extensively in many cultures since ancient times as antiseptic, wound healing, anti-pyretic and others due to its biological and pharmacological properties, such as immunomodulatory, antitumor, anti-inflammatory, antioxidant, antibacterial, antiviral, antifungal, antiparasite activities. But despite its broad and traditional use, there is little knowledge about its potential interaction with prescription drugs. AIM OF THE STUDY: The main objective of this work was to study the potential herbal-drug interactions (HDIs) of EPP-AF® using an in vivo assay with a cocktail approach. MATERIALS AND METHODS: Subtherapeutic doses of caffeine, losartan, omeprazole, metoprolol, midazolam and fexofenadine were used. Sixteen healthy adult volunteers were investigated before and after exposure to orally administered 125 mg/8 h (375 mg/day) EPP-AF® for 15 days. Pharmacokinetic parameters were calculated based on plasma concentration versus time (AUC) curves. RESULTS: After exposure to EPP-AF®, it was observed decrease in the AUC0-∞ of fexofenadine, caffeine and losartan of approximately 18% (62.20 × 51.00 h.ng/mL), 8% (1085 × 999 h.ng/mL) and 13% (9.01 × 7.86 h.ng/mL), respectively, with all 90% CIs within the equivalence range of 0.80-1.25. On the other hand, omeprazole and midazolam exhibited an increase in AUC0-∞ of, respectively, approximately 18% (18.90 × 22.30 h.ng/mL) and 14% (1.25 × 1.43 h.ng/mL), with the upper bounds of 90% CIs slightly above 1.25. Changes in pharmacokinetics of metoprolol or its metabolite α-hydroxymetoprolol were not statistically significant and their 90% CIs were within the equivalence range of 0.80-1.25. CONCLUSIONS: In conclusion, our study shows that EPP-AF® does not clinically change CYP1A2, CYP2C9, CYP2C19, CYP2D6 and CYP3A activities, once, despite statistical significant, the magnitude of the changes in AUC values after EPP-AF® were all below 20% and therefore may be considered safe regarding potential interactions involving these enzymes. Besides, to the best of our knowledge this is the first study to assess potential HDIs with propolis.

A UHPLC-MS/MS method coupled with liquid-liquid extraction for the quantitation of phenacetin, omeprazole, metoprolol, midazolam and their metabolites in rat plasma and its application to the study of four CYP450 activities.

Drug-drug interactions (DDIs) are thought to be associated with the inhibition of cytochrome P450 activities. The cocktail method with analysis of the metabolism of two or more probe drugs is used to determine CYP450 activities. In this study, we established a UHPLC-MS/MS method for simultaneous quantitation of four CYP450 probe drugs (phenacetin, omeprazole, metoprolol and midazolam) and their metabolites (acetaminophen, 5'-hydroxy omeprazole, α-hydroxy metoprolol and 1'-hydroxy midazolam) in rat plasma. Sample preparation by plasma protein precipitation was combined with a liquid-liquid extraction method. The separation was carried out on a ZORBAX Eclipse Plus C18 Rapid Resolution High Definition column with a gradient elution, using water containing 0.1% formic acid (A) and acetonitrile (B) in a run time of only 3.0 min. Detection was conducted with a 6420 series triple-quadrupole tandem mass spectrometer, using ESI in positive ion mode with multiple reaction monitoring (MRM). The calibration curves were linear over the concentration range 10-5000 ng/mL for phenacetin, omeprazole, metoprolol and midazolam, and 1-500 ng/mL for their metabolites. Intra- and inter-day precisions were within 15%, and the accuracies were in the range of 87-112%. The method was successfully applied to the pharmacokinetic study of probe drugs/metabolites and DDIs with 3-n-butylphthalide (NBP) after administration of a single oral dose of phenacetin, omeprazole, metoprolol and midazolam in rats.

Lack of Effect of 12-Week Treatment with Risankizumab on the Pharmacokinetics of Cytochrome P450 Probe Substrates in Patients with Moderate to Severe Chronic Plaque Psoriasis.

OBJECTIVE: The objective of this study was to characterize the effects of risankizumab on the in vivo activity of cytochrome P450 (CYP) 1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A in psoriasis patients using a cocktail approach. METHODS: Patients with moderate to severe chronic plaque psoriasis (n = 21) received single oral doses of sensitive probe substrates for CYP1A2 (caffeine 100 mg), CYP2C9 (warfarin 10 mg), CYP2C19 (omeprazole 20 mg), CYP2D6 (metoprolol 50 mg), and CYP3A (midazolam 2 mg) on day 1, followed by 12 weeks of subcutaneous risankizumab treatment of 150 mg once every 4 weeks from day 8 to day 92, and again the same cocktail of substrates on day 98. Serial blood samples were collected for determination of the CYP probe drugs and metabolites with and without risankizumab. Trough samples were collected for risankizumab. RESULTS: The 90% confidence intervals (CIs) for the area under the plasma concentration-time curve (AUC) from time zero to infinity (AUC∞) ratios for the CYP probe substrates administered with risankizumab versus without risankizumab were within the default 0.8-1.25 equivalence bounds. Similar results were observed for maximum plasma concentration (Cmax), except for omeprazole, for which the lower bound of the 90% CI for Cmax (0.73) extended slightly below the default equivalence limit. No differences were observed in metabolite-to-parent drug Cmax or AUC ratios with risankizumab versus without risankizumab. Risankizumab trough plasma concentrations significantly exceeded those of the phase III regimen of risankizumab in psoriasis (150 mg subcutaneously at weeks 0 and 4 and every 12 weeks thereafter). CONCLUSIONS: Risankizumab did not affect the in vivo activity of CYP1A2, CYP2C9, CYP2C19, CYP2D6, or CYP3A enzymes in patients with moderate or severe plaque psoriasis and therefore has no potential for drug interactions through these enzymes. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02772601.

Comparative pharmacokinetics of Omeprazole and its metabolites in poor and extensive metabolizer Pakistani healthy volunteers and a review of different studies.

This study was designed to evaluate a comparative single dose (40mg) pharmacokinetics (PK) of Omeprazole (OMP) and its two metabolites, 5-hydroxy Omeprazole (5-OH-OMP) and Omeprazole sulphone (OMP-S) in poor (PM) and extensive (EM) metabolizer Pakistani healthy adult volunteers. The frequency of CYP2C19 and CYP3A4 varies widely in different populations. The present study was conducted to evaluate the PK of OMP and its two metabolites in Pakistani population and to review different studies conducted after administration of single dose of OMP. Twenty two subjects were enrolled in this study and divided into two groups. The CYP2C19 phenotyping was evaluated by the metabolic ratio of OMP to 5-OH-OMP. It was a single dose, open label study and the blood samples from subjects were collected at different time intervals until 24 hours. The PK parameters were calculated using the PK-summit software. The metabolic ratio of area under the plasma concentration-time curve AUCOMP/5-OH-OMP was 1.86 ± 0.572 and13.84 ± 2.504 for EM and PM, respectively; maximum plasma concentration (Cmax) of OMP was increased by two folds for PM while the AUC∞ was increased by 3 folds; the Cmax and AUC∞ of 5-OH-OMP decreased for PM by 2 folds while there was 3 fold increase observed in the Cmax and AUC∞ of OMP-S. The PK of OMP and its metabolites in different populations were also discussed, and issues regarding CYP2C19 and CYP3A4 genotyping were also extensively reviewed. In EM of CYP2C19 the concentration of 5-OH-OMP is higher while that of OMP-S is lower. This study as well as reported studies reveals that in PM of CYP2C19 more drugs are available for CYP3A4 to be metabolized. A correlation between CYP2C19 EM and PM activity with CYP3A4 needs to be established.

Evaluation of Omeprazole Limited Sampling Strategies to Estimate Constitutive Cytochrome P450 2C19 Activity in Healthy Adults.

BACKGROUND: Limited sampling strategy (LSS) is a validated method to estimate pharmacokinetic (PK) parameters from a reduced number of samples. Omeprazole is used to phenotype in vivo cytochrome P450 (CYP) 2C19 activity. This study examined an LSS using 2 estimation methods to determine apparent oral clearance (CL/F) and thus CYP2C19 activity. METHODS: Data from 7 previously published studies included healthy subjects receiving a single, oral dose of omeprazole with intensive PK sampling. CL/F was estimated using noncompartmental analysis (NCA) and population PK modeling. LSS was simulated by selecting the 1, 2, 4, and/or 6-hour postdose time points. Linear regression was performed to assess whether CL/F estimated from limited sampling could accurately predict CL/F from the full PK profile. RESULTS: Median CL/F was 23.7 L/h by NCA and 19.3 L/h by population PK modeling. In comparing the LSS NCA estimated versus observed CL/F, all evaluated linear regression models had unacceptable coefficients of determination (r, range: 0.14-0.81). With the population PK approach, 737 plasma concentrations (n = 71) and CYP2C19 genotype data were described with a 1-compartment structural model with mixed zero and first-order absorption and lag time. In comparing the population PK LSS estimated versus observed CL/F, all evaluated linear regression models had unacceptable r (range: 0.02-0.74). Post hoc comparison of CYP2C19 poor metabolizers versus CYP2C19 extensive metabolizers resulted in significantly lower CL/F in poor metabolizers versus extensive metabolizers. CONCLUSIONS: Omeprazole LSS performed poorly in estimating CL/F using 2 separate estimation approaches and does not seem to be a suitable method for determining CYP2C19 activity.

The pH-altering agent omeprazole affects rate but not the extent of ibrutinib exposure.

PURPOSE: This drug-interaction study evaluated the effect of omeprazole, a proton-pump inhibitor, on ibrutinib's pharmacokinetics (PK) in healthy participants. METHODS: This open-label, sequential-design study included 20 healthy adults aged 18-55 years. Ibrutinib (560 mg, single dose) was administered after an overnight fast alone on day 1 and with omeprazole on day 7. Omeprazole (40 mg) alone was administered on days 3-6, 1 h before breakfast; and after an overnight fast on day 7, followed by ibrutinib 2 h later. Blood was sampled on days 1 and 7 for up to 48 h postdose, and the standard PK parameters for ibrutinib and PCI-45227 were summarized using descriptive statistics. The effect of omeprazole on ibrutinib's PK was determined by assessing geometric mean ratios (GMRs) and 90% CIs. Mechanistic modeling was performed using the BTK-receptor occupancy (RO) model. RESULTS: AUC48h and AUClast of ibrutinib plus omeprazole versus ibrutinib alone showed a modest decrease (GMR [90% CI] 98.3% [83.1-116.3] and 92.5% [77.8-109.9], respectively); Cmax decreased by 62.5% (GMR [90% CI] 37.5% [26.4-53.4]), with delayed tmax (1-2 h) and terminal half-life unaffected. Mean AUC for PCI-45227 (primary metabolite) was ~ 20% lower with ibrutinib plus omeprazole versus ibrutinib alone. Model predictions showed no impact of decreased Cmax on BTK target engagement. No new safety signals were identified with the use of ibrutinib in this study. CONCLUSIONS: The decrease in Cmax without a corresponding decrease in AUC by omeprazole was not clinically relevant for ibrutinib's bioavailability. No dose adjustments are recommended during ibrutinib's co-administration with omeprazole or other pH-altering agents.

Disposition kinetics of omeprazole in healthy female volunteers in Faisalabad.

Omeprazole (OMP) a proton pump inhibitor is widely used to suppress gastric acid secretions of parietal cells of stomach and metabolized predominantly by CYP2C19. The objective of the present study was to investigate the pharmacokinetics and dosage regimen of OMP, after its single oral administration in eight healthy adult female subjects. Blood samples were collected at different time intervals after oral administration and their pH was measured. Plasma concentration of OMP was determined by high performance liquid chromatography (HPLC) system equipped with UV-visible Detector. The concentration versus time data was used to compute the pharmacokinetic parameters with the help of computer software programme MW/PHRAM APO version 3.02.Peak plasma concentration was (Cmax) 0.38±0.04 µg/ml achieved at 2.07±0.22 hrs. The elimination half-life (t1/2 ß) was1.82 ± 0.42 hrs. Volume of distribution (Vd) in the present study was 0.40 ± 0.07 l/kg with total body clearance (ClB) 0.19 ± 0.02 l/hr/kg and area under the curve (AUC) 1.89 ± 0.23 µg.hr/ml.The pharmacokinetic properties which are different from the literature after oral administration of 20 mg OMP in eight healthy female volunteers may be due to the variations of environment and genetic variation between Pakistan and drug manufacturing of foreign countries.

Developmental pharmacogenetics of CYP2C19 in neonates and young infants: omeprazole as a probe drug.

AIMS: Although substantial progress has been made in understanding of ontogeny of drug metabolism, there is still a gap of knowledge in developmental pharmacogenetics in neonates. We hypothesized that both age and pharmacogenetics might explain the developmental pattern of CYP2C19. We conducted a population pharmacokinetic-pharmacogenetic study to quantify the developmental pharmacogenetics of CYP2C19 in neonates and young infants using omeprazole as a probe drug. METHODS: Pharmacokinetic samples were collected from 51 Caucasian neonates and young infants, who were receiving omeprazole treatment. Population pharmacokinetic-pharmacogenetic analysis of omeprazole and its metabolites was performed using NONMEM. RESULTS: Data fitted a one-compartment parent and metabolite model with first-order absorption and elimination. CYP2C19 and CYP3A4 are predominantly involved in the metabolism of omeprazole despite their relatively low activities compared to adults. The clearance of omeprazole converted to 5-hydroxy-omeprazole (CLOMZ-M1 ) increases with postnatal age. In CYP2C19 poor and intermediate metabolizers, model-predicted CLOMZ-M1 are 12.5% (5-95% percentile: 3-14.9%) and 44.9% (5-95% percentile: 29.9-72.6%) of the value in extensive/ultrarapid metabolizer, respectively. Model-predicted absorption rate constant of omeprazole is 6.93 (5-95% percentile: 3.01-14.61) times higher in ABCB1 homozygous mutant patients, 1.86 (5-95% percentile: 0.86-3.47) times higher in ABCB1 heterozygous patients than that in ABCB1 homozygous wild-type patients. CONCLUSIONS: Developmental pharmacogenetics of CYP2C19 was quantitatively described in neonates and young infants using omeprazole as a probe drug. Our findings emphasize the importance of semiphysiological developmental pharmacokinetic modelling approach when evaluating developmental pharmacogenetics of drugs with multiple routes of biotransformation.

Effects of aging and rifampicin pretreatment on the pharmacokinetics of human cytochrome P450 probes caffeine, warfarin, omeprazole, metoprolol and midazolam in common marmosets genotyped for cytochrome P450 2C19.

1. The pharmacokinetics were investigated for human cytochrome P450 probes after single intravenous and oral administrations of 0.20 and 1.0 mg/kg, respectively, of caffeine, warfarin, omeprazole, metoprolol and midazolam to aged (10-14 years old, n = 4) or rifampicin-treated/young (3 years old, n = 3) male common marmosets all genotyped as heterozygous for a cytochrome P450 2C19 variant. 2. Slopes of the plasma concentration-time curves after intravenous administration of warfarin and midazolam were slightly, but significantly (two-way analysis of variance), decreased in aged marmosets compared with young marmosets. The mean hepatic clearances determined by in silico fitting for individual pharmacokinetic models of warfarin and midazolam in the aged group were, respectively, 23% and 56% smaller than those for the young group. 3. Significantly enhanced plasma clearances of caffeine, warfarin, omeprazole and midazolam were evident in young marmosets pretreated with rifampicin (25 mg/kg daily for 4 days). Two- to three-fold increases in hepatic intrinsic clearance values were observed in the individual pharmacokinetic models. 4. The in vivo dispositions of multiple simultaneously administered drugs in old, young and P450-enzyme-induced marmosets were elucidated. The results suggest that common marmosets could be experimental models for aged, induced or polymorphic P450 enzymes in P450-dependent drug metabolism studies.

Evaluation of the pharmacokinetic drug interaction potential of tivantinib (ARQ 197) using cocktail probes in patients with advanced solid tumours.

AIMS: This phase 1, open-label, crossover study sought to evaluate drug-drug interactions between tivantinib and cytochrome P450 (CYP) substrates and tivantinib and P-glycoprotein. METHODS: The effect of tivantinib doses on the pharmacokinetics of the probe drugs for CYP1A2 (caffeine), CYP2C9 (S-warfarin), CYP2C19 (omeprazole), and CYP3A4 (midazolam), and for P-glycoprotein (digoxin) was investigated in 28 patients with advanced cancer using a cocktail probe approach. Patients received single doses of probe drugs alone and, after 5 days of treatment, with tivantinib 360 mg twice daily. RESULTS: The ratios of geometric least squares mean (90% confidence interval) for the area under the concentration-time curve from time zero to the last quantifiable concentration in the presence/absence of tivantinib were 0.97 (0.89-1.05) for caffeine, 0.88 (0.76-1.02) for S-warfarin, 0.89 (0.60-1.31) for omeprazole, 0.83 (0.67-1.02) for midazolam, and 0.69 (0.51-0.94) for digoxin. Similar effects were observed for maximum plasma concentrations; the ratio for digoxin in the presence/absence of tivantinib was 0.75 (0.60-0.95). CONCLUSIONS: The data suggest that tivantinib 360 mg twice daily has either a minimal or no effect on the pharmacokinetics of probe drugs for CYP1A2, CYP2C9, CYP2C19 and CYP3A4 substrates, and decreases the systemic exposure of P-glycoprotein substrates when administered with tivantinib.