Apparent Total Clearance Research Articles

CYP2D1 Gene Knockout Reduces the Metabolism and Efficacy of Venlafaxine in Rats.

Rat CYP2D1 has been considered as an ortholog of human CYP2D6 To assess the role of CYP2D1 in physiologic processes and drug metabolism, a CYP2D1-null rat model was generated with a CRISPR/Cas9 method. Seven base pairs were deleted from exon 4 of CYP2D1 of Sprague-Dawley wild-type (WT) rats. The CYP2D1-null rats were viable and showed no abnormalities in general appearance and behavior. The metabolism of venlafaxine (VLF) was further studied in CYP2D1-null rats. The V max and intrinsic clearance of the liver microsomes in vitro from CYP2D1-null rats were decreased (by ∼46% and ∼57% in males and ∼47% and ∼58% in females, respectively), while the Michaelis constant was increased (by ∼24% in males and ∼25% in females) compared with WT rats. In the pharmacokinetic studies, compared with WT rats, VLF in CYP2D1-null rats had significantly lower apparent total clearance and apparent volume of distribution (decreased by ∼36% and ∼48% in males and ∼23% and ∼25% in females, respectively), significantly increased area under the curve (AUC) from the time of administration to the last time point, AUC from the start of administration to the theoretical extrapolation, and C max (increased by ∼64%, ∼59%, and ∼26% in males and ∼43%, ∼35%, and ∼15% in females, respectively). In addition, O-desmethyl venlafaxine formation was reduced as well in CYP2D1-null rats compared with that in WT rats. Rat depression models were developed with CYP2D1-null and WT rats by feeding them separately and exposing them to chronic mild stimulation. VLF showed better efficacy in the WT depression rats compared with that in the CYP2D1-null rats. In conclusion, a CYP2D1-null rat model was successfully generated, and CYP2D1 was found to play a certain role in the metabolism and efficacy of venlafaxine. SIGNIFICANCE STATEMENT: A novel CYP2D1-null rat model was generated using CRISPR/Cas9 technology, and it was found to be a valuable tool in the study of the in vivo function of human CYP2D6. Moreover, our data suggest that the reduced O-desmethyl venlafaxine formation was associated with a lower VLF efficacy in rats.

Racial difference in bioavailability of oral ibandronate between Caucasian and Taiwanese postmenopausal women.

Interethnic differences in the pharmacokinetics of oral ibandronate for osteoporosis are unknown. We compared the disposition of oral ibandronate between Caucasian and Taiwanese postmenopausal women. Ibandronate 150mg was administered to 35 Caucasian and 16 Taiwanese postmenopausal women in two separate phase 1 studies. Interethnic comparisons were performed to assess pharmacokinetic properties, including the area under the concentration-time curve (AUC), peak concentration (Cmax), elimination half-life, urinary drug recovery (Ae%), renal clearance (CLr), apparent total clearance (CL/F), and apparent volume of distribution (Vd/F). The mean AUC, Cmax, and Ae% were 2.41-, 1.69-, and 2.95-fold greater in the Taiwanese than in the Caucasian subjects, and the average CL/F and Vd/F were 2.48- and 2.46-fold smaller. There were no significant differences in mean CLr and half-life between both groups. As bisphosphonates are not biotransformed but are mainly excreted in the urine, the total body clearance is close to the CLr. These results suggested a larger bioavailability in the Taiwanese group which resulted in the differences in the CL/F and Vd/F. Multiple linear regression analysis demonstrated ethnicity influences of the pharmacokinetic properties after adjusting for the other variables. Bioavailability was largely responsible for the interethnic pharmacokinetic differences following oral administration of 150mg ibandronate and seemed greater in the Taiwanese compared with the Caucasian subjects. Further dose-ranging studies are warranted to determine the optimal dosages of oral ibandronate in patients of Asian or Taiwanese ethnicity.

Prospective study of the changes in pharmacokinetics of immunosuppressive medications after laparoscopic sleeve gastrectomy.

Laparoscopic sleeve gastrectomy induces weight loss via the creation of a restrictive gastric tube for early satiety and is associated with an accelerated gastric transit time. A prospective, single-dose pharmacokinetic study was performed, prior to and after laparoscopic sleeve gastrectomy, for tacrolimus, extended-release tacrolimus, mycophenolate mofetil, and enteric-coated mycophenolate sodium. The study included 12 morbidly obese patients in chronic renal failure. The median decrease in body mass index was 8.8kg/m2 with an excess body weight loss of 54.9%. The AUC24 of all drugs were increased after laparoscopic sleeve gastrectomy by 46%, 55%, 77%, and 74%, respectively. The maximum concentrations were increased for tacrolimus, extended-release tacrolimus, and mycophenolate mofetil by 43%, 46%, and 65%. The apparent total clearances were decreased for tacrolimus, mycophenolate mofetil, and enteric-coated mycophenolate sodium by 36%, 57%, and 38%. Laparoscopic sleeve gastrectomy can be associated with significant changes in pharmacokinetics of the drugs evaluated. The mechanism is likely decreased apparent drug clearance due to an increased drug exposure (from a more distal site of intestinal absorption with decreased intestinal metabolism), or decreased clearance (liver metabolism). Adapting the monitoring of immunosuppression will be important to avoid overdosing and potential side effects.

Simultaneous analysis of the total plasma concentration of atorvastatin and its five metabolites and the unbound plasma concentration of atorvastatin: Application in a clinical pharmacokinetic study of single oral dose

Atorvastatin (ATV) and its two active metabolites, o-hydroxy atorvastatin acid (o-OH-ATV) and p-hydroxy atorvastatin acid (p-OH-ATV) are responsible for its HMG-CoA (3-hydroxy-3-methylglutaryl-coenzyme-A) reductase inhibitory activity, while its corresponding inactive lactone forms (LAC) are related to the manifestation of myopathy. The present study reports the development and validation of a method for the simultaneous analysis of ATV and its five metabolites (o-OH-ATV, p-OH-ATV, ATV-LAC, o-OH-ATV-LAC, p-OH-ATV-LAC) as total plasma concentration and ATV as unbound plasma concentration using UPLC-MS/MS. The method was applied in a pharmacokinetic study following administration of a single oral 20, 40 or 80 mg ATV dose in healthy volunteers (n = 15). ATV and its five metabolites were separated on a C18 column using as mobile phase a mixture of 0.2% formic acid and acetonitrile (55:45, v/v) at a flow of 0.4 mL/min. The method showed linearity from 25 pg/mL to 200 ng/mL plasma as total concentration and from 6.25 pg to 25 ng/mL plasma ultrafiltrate as ATV unbound concentration. The coefficients of variation and the relative standard errors of the accuracy and precision analyses were <15%. The method allowed quantification of plasma concentrations of ATV and its five metabolites up to 36 h after 20, 40 or 80 mg ATV administration. The pharmacokinetic parameters dose normalized to 20 mg are presented as follow (n = 15, mean): unbound fraction 9.38%, maximum plasma concentration 9.52 ng/mL, time to reach maximum plasma concentration 0.98 h, apparent total clearance 742.90 L/h, apparent distribution volume 9005 L, and AUC metabolite/ATV ratios 0.06 for p-OH-ATV, 0.94 for o-OH-ATV, 1.43 for ATV-LAC, 0.25 for p-OH-ATV-LAC and 1.75 for o-OH-ATV-LAC. In conclusion, the methods for simultaneous analysis of ATV and its five metabolites as total plasma concentration and ATV as the unbound plasma concentration showed sensitivity, linearity, precision and accuracy compatible with application in pharmacokinetic studies of single oral dose of 20, 40 or 80 mg ATV.

Steady-state population pharmacokinetics of terizidone and its metabolite cycloserine in patients with drug-resistant tuberculosis.

Despite terizidone being part of the second-line recommended drugs for treatment of drug-resistant tuberculosis (DR-TB), information on its pharmacokinetics is scarce. The aim of this study was to describe the steady-state population pharmacokinetics (PPK) of terizidone and its primary metabolite cycloserine in patients with DR-TB and determine the effect of patient characteristics. This clinical study involved 39 adult DR-TB patients admitted to Brewelskloof Hospital in Cape Town, South Africa for intensive treatment phase. Blood samples were collected at predose and 0.5, 1, 2, 3, 3.5, 4, 8, 16 and 24hours after drug administration. The estimation of PPK parameters was performed using nonlinear mixed-effects modelling software Monolix 2018R1. Free-fat mass was used to perform allometric scaling on disposition parameters. A 1-compartment model best described the pharmacokinetics of terizidone and cycloserine. A modified transit compartment model described the absorption of terizidone. The parameters of terizidone model were mean transit time (1.7h), absorption rate constant (2.97h-1 ), apparent volume of distribution (Vp/F: 13.4L) and apparent total clearance (0.51Lh-1 ). In the joint model, apparent fraction of terizidone converted to cycloserine was 0.29 while apparent clearance of terizidone via other routes and apparent cycloserine clearance was 0.1Lh-1 and 2.94Lh-1 , respectively. Serum albumin had significant effect on Vp/F. The developed PPK model described well the concentration-time profile for terizidone and cycloserine in DR-TB patients. High albumin concentration was associated with low Vp/F.

UPLC-MS/MS method for gemfibrozil determination in plasma with application to a pharmacokinetic study in healthy Brazilian volunteers

Gemfibrozil (GFZ) is a derivative of fibric acid and is used in the treatment of dyslipidemia. GFZ may affect the metabolism of various drugs, including statins, by inhibiting the sinusoidal influx transporter OATP1B1 and also CYP2C9 and CYP2C8 enzymes. This study presents the development and validation of a rapid, simple, sensitive and reproducible method of GFZ analysis in human plasma using UPLC-MS/MS. The method was applied in a pharmacokinetic study following administration of multiple doses of 600 mg GFZ every 12 h in healthy volunteers (n = 15). GFZ was separated on a C18 column using a mixture of 0.01% formic acid and acetonitrile (40:60, v/v) as the mobile phase at a flow rate of 0.4 mL/min. The method showed linearity in the range from 0.01 μg/mL to 100 μg/mL plasma. The coefficients of variation and the relative standard errors of the accuracy and precision analyses were <15%. The method allowed quantification of plasma concentrations of GFZ in the dose interval of the sixth day of administration of multiple oral doses of GFZ every 12 h. The pharmacokinetic parameters are presented as mean (95% CI): area under the plasma concentration versus time curve 88.84 (72.72–104.96) μg·h/mL, steady state mean plasma concentration 7.40 (6.06–8.75) μg/mL, minimum plasma concentration 1.24 (0.87–1.61) μg/mL, maximum plasma concentration 26.73 (21.31–32.15) μg/mL, time to reach maximum plasma concentration 2.28 (1.42–3.13) h, elimination half-life 2.81 (2.22–3.40) h, apparent total clearance 7.72 (5.85–9.58) L/h, apparent distribution volume 33.97 (18.41–49.53) L. In conclusion, the method for analysis of GFZ in human plasma showed sensitivity, linearity, precision and accuracy compatible with application in pharmacokinetic studies of multiple oral dose of 600 mg GFZ every 12 h.

SAT-443 Osilodrostat Has No Clinically Relevant Effect on the Pharmacokinetic (PK) Profile of a Monophasic Oral Contraceptive in Healthy Females Receiving Cortisol Replacement Therapy

Background: Osilodrostat, a potent oral 11β-hydroxylase inhibitor, is in Phase 3 development for endogenous Cushing’s syndrome (CS). As CS occurs mostly in females of childbearing age, it is important to determine the effect of osilodrostat on oral contraceptives (OCs). We report the effect of multiple osilodrostat doses on the PK profile of a single OC dose in healthy females on cortisol replacement. Methods: This Phase 1, single-center, open-label, three-period, drug-drug interaction study enrolled healthy, non-smoking females aged 18-50 y with regular menstrual cycles. A single OC dose, containing ethinyl estradiol (EES) 30 μg and levonorgestrel (LVG) 150 μg, was given on day (D) 1 of treatment period 1 (TP1; D1-7). In TP2 (D8-19), osilodrostat 30 mg twice daily was given with hydrocortisone 20 mg daily; a second OC dose was given on D15. Hydrocortisone was tapered/discontinued during TP3 (D20-28). Primary variable: AUClast (area under curve from time 0 to last measurable concentration) and Cmax (peak plasma concentration) of EES and LVG, calculated from a 120h OC PK profile on D1 and D15. Secondary endpoints: osilodrostat PK; safety/tolerability of OC and osilodrostat co-administration. Results: 24 subjects were enrolled (mean ± SD age, 37 ± 7 years; Caucasian, 96%). EES and LVG AUClast were similar when OC was given with osilodrostat (n=19) vs alone (n=24) [geometric mean: EES, 541 vs 537 pg∙h/mL; LVG, 44900 vs 42300 pg∙h/mL]. Insignificant decreases in Cmax were seen for OC with osilodrostat vs alone (geometric mean: EES, 51.6 vs 59.8 pg/mL; LVG, 3360 vs 3800 pg/mL). Apparent total clearance, t½ (half-life) and tmax (time to Cmax) were similar with and without osilodrostat for EES and LVG, except for a small increase in t½ of LVG with osilodrostat (26.4 vs 22.9 h). For osilodrostat PK (n=19), geometric means for AUCτ (AUC to end of dosing period at steady state) and Cmax, and median tmax, were 1620 ng∙h/mL, 299 ng/mL, and 1.0 h, respectively. Most (92%) subjects received both OC doses; 83% completed osilodrostat treatment. At the end of TP3 (2 days after last hydrocortisone dose), 79% of subjects had ACTH-stimulated serum cortisol below the protocol-defined threshold, although all had normal unstimulated levels at study end; these results may be related to high osilodrostat doses, hydrocortisone supplementation, timing of first stimulation test after last hydrocortisone dose or another factor. Other common AEs: nausea (46%), headache and nasopharyngitis (both 38%). Four (17%) subjects discontinued due to: palpitations, n=1; throat tightness, n=1; asthenia and exhaustion, n=1; positive pregnancy test, n=1 (not confirmed by ultrasound). Conclusion: Concomitant treatment of osilodrostat (highest dose used in Phase 3 trials) with a single OC dose did not result in clinically relevant changes in OC PK parameters, suggesting that OC can be given with osilodrostat and provide adequate contraception.

Population Pharmacokinetics and Exposure-Response Relationships of Naldemedine

ABSTRACTPurposeTo characterize population pharmacokinetic (PK) of naldemedine, to identify factors which influence naldemedine PK, and to evaluate their clinical relevancy based on exposure-response relationships.MethodsA population PK model was developed with pooled naldemedine concentrations from healthy subjects, patients with chronic non-cancer pain and opioid-induced constipation (OIC), and cancer patients with OIC. Exposure-response analyses were performed with efficacy (responder or non-responder) and safety (occurrence of gastrointestinal disorders or not) data in phase 2b and phase 3 studies.ResultsNaldemedine plasma concentrations were adequately described by a 2-compartment model with first-order absorption and absorption lag time. The final model included the effects of age, creatinine clearance, race, and gender on apparent total clearance; the effects of body weight, health status, and food condition on apparent volume of central compartment; and the effect of age on first-order rate of absorption. When subjects took 0.2 mg of naldemedine once daily, the probability of spontaneous bowel movement (SBM) responders was predicted to be approximately 50%, while that of severe gastrointestinal disorders was predicted to be less than 3%. The influence of the covariates on PK was not considered clinically significant because similar efficacy and safety were expected based on the exposure-response analysis.ConclusionsThe covariates are identified in the population PK analysis; however, no dose-adjustment is required for them based on the exposure-response analysis.

Population pharmacokinetics of nintedanib in patients with idiopathic pulmonary fibrosis

BackgroundNintedanib is a potent intracellular inhibitor of tyrosine kinases, including the receptor kinases vascular endothelial growth factor, platelet-derived growth factor and fibroblast growth factor. A previous model assessed the population pharmacokinetics of nintedanib and its main metabolite BIBF 1202 in patients with non-small cell lung cancer and idiopathic pulmonary fibrosis (IPF). The objective of this analysis was to further characterise the population pharmacokinetics of nintedanib in patients with IPF by including data from the Phase III trials. MethodsWe pooled data from 933 patients with IPF participating in the Phase II TOMORROW trial and the two Phase III INPULSIS trials. Plasma concentrations of nintedanib (n = 3501) were analysed using nonlinear mixed-effects modelling. ResultsPharmacokinetics of nintedanib was described by a one-compartment model with linear elimination, first-order absorption and an absorption lag time. The population estimates of absorption rate, lag time, apparent total clearance and apparent volume of distribution at steady state for a typical IPF patient were 0.0814 h−1, 0.689 h, 994 L/h, and 265 L. The model confirmed age, body weight, smoking and Asian race (with different effect sizes in different Asian subpopulations) as statistically significant covariates influencing nintedanib exposure. Serum lactate dehydrogenase levels were identified as another factor significantly influencing nintedanib plasma concentrations. No individual covariate at extreme values (5th and 95th percentiles of baseline for continuous covariates) resulted in changes in exposure of more than 50% relative to a typical patient. ConclusionsThe developed model provides further details about the pharmacokinetics of nintedanib in patients with IPF and can be used for simulations exploring covariate effects and exposure-response analyses in this patient population.

Population pharmacokinetics of nintedanib, an inhibitor of tyrosine kinases, in patients with non-small cell lung cancer or idiopathic pulmonary fibrosis

PurposeA population pharmacokinetic model was developed for nintedanib in patients with non-small cell lung cancer (NSCLC) or idiopathic pulmonary fibrosis (IPF). The effects of intrinsic and extrinsic patient factors on exposure of nintedanib and its main metabolite BIBF 1202 were studied.MethodsData from 1191 patients with NSCLC (n = 849) or IPF (n = 342) treated with oral nintedanib (once- or twice-daily, dose range 50–250 mg) in 4 Phase II or III studies were combined. Plasma concentrations of nintedanib (n = 5611) and BIBF 1202 (n = 5376) were analyzed using non-linear mixed-effects modeling.ResultsPharmacokinetics of nintedanib were described by a one-compartment model with linear elimination, first-order absorption, and absorption lag time. For a typical patient, the absorption rate was 0.0827 h−1, apparent total clearance was 897 L/h, apparent volume of distribution at steady state was 465 L, and lag time was 25 min. Age, weight, smoking, and Asian race were statistically significant covariates influencing nintedanib exposure, but no individual covariate at extreme values (5th and 95th percentiles of baseline values for continuous covariates) resulted in a change of more than 33% relative to a typical patient. Pharmacokinetics and covariate effects for BIBF 1202 were similar to nintedanib. Mild or moderate renal impairment and mild hepatic impairment (classified by transaminase or bilirubin increase above the upper limit of normal) or underlying disease had no significant effects on nintedanib pharmacokinetics.ConclusionsThis model adequately described the pharmacokinetic profile of nintedanib in NSCLC and IPF populations and can be used for simulations exploring covariate effects and exposure–response analyses.

In vivo schistosomicidal activity of 7-epiclusianone and its quantification in the plasma of healthy and Schistosoma mansoni infected mice using UPLC-MS/MS

BackgroundThe tetraprenylated benzophenone 7-epiclusianone (7-epi) is a substance isolated from the fruits of Garcinia brasiliensis and in vitro studies have demonstrated that 7-epi is effective against Schistosoma mansoni adult worms. Hypothesis/PurposeHere we report the in vivo evaluation of 7-epi and its pharmacokinetic in healthy and Schistosoma mansoni infected mice. Study design and methodsIn this work, we assayed the schistosomicidal activity of 7-epi at the dose of 100 mg/kg and 300 mg/kg body weight/day in S. mansoni experimentally infected mice. Besides, two groups of animals were treated and a detailed analysis of plasma samples was performed by liquid chromatography coupled to mass spectrometry (LC-MS/MS). ResultsThe worm burden showed a reduction in the infected mice after treatment with 300 mg/kg for five days (p < .05). And we found an increase of AUC0–∞ (20846 vs. 32438 ng.h/ml) and a decrease of total apparent clearance (0.006 vs. 0.004 l/h/kg) of 7- epi in the infected group compared to the healthy group. Consequently, the half-life increased (1.73 vs. 6.11 h) and Cmax was reduced (5427.5 vs. 3321.0 ng/ml) in the infected group compared to the healthy group. In addition, histopathological investigations were performed analysing liver samples from healthy and infected mice. ConclusionThe results showed significant schistosomicidal in vivo activity at 300 mg/kg. In addition, livers from S. mansoni infected mice showed a greater number of egg granulomas and the changes in the pharmacokinetic parameters in this group could be associated with the pathology of the murine experimental schistosomiasis.

Pharmacokinetic interactions in mice between irinotecan and MBL-II-141, an ABCG2 inhibitor.

The chromone derivative MBL-II-141, specifically designed to inhibit ABCG2, was previously demonstrated to combine strong inhibition potency, low toxicity and good efficiency in reversing resistance to irinotecan in a xenografted mouse model. Here, the pharmacokinetic interactions in mice between irinotecan, its active metabolite SN-38 and MBL-II-141 were characterized quantitatively in the blood and in the brain. Compartmental models were used to fit the data. Goodness-of-fit was assessed by simulation-based diagnostic tools. Irinotecan increased the MBL-II-141 apparent clearance and Vss 1.5-fold, probably by increasing the MBL-II-141 unbound fraction. MBL-II-141 decreased the total apparent clearance of irinotecan by 23%, by decreasing its biliary clearance. MBL-II-141 increased 3-fold the brain accumulation of irinotecan, as a result of the rise of systemic exposure combined with the inhibition of ABCG2-mediated efflux at the blood-brain barrier. Finally, SN-38 exposure was increased by 1.16-fold under treatment with MBL-II-141, owing to the higher irinotecan exposure with increased metabolism towards the formation of SN-38. These results may help to anticipate the pharmacokinetic interactions between MBL-II-141 and other ABCG2 substrates. The irinotecan-MBL-II-141 interaction is also expected to occur in humans. Copyright © 2017 John Wiley & Sons, Ltd.

Population pharmacokinetic analysis of rebamipide in healthy Korean subjects with the characterization of atypical complex absorption kinetics.

In this study, the population pharmacokinetic (PK) analysis of rebamipide (Reba) in healthy male Korean subjects was analyzed using the nonlinear mixed effects modeling method. The possible effects of physiological covariates and the multidrug resistance (MDR1) gene 3435C>T polymorphism on PK parameters were also investigated. Data were collected from a bioequivalence study, in which 26 subjects who participated in the study were administered a single oral dose of 100mg Reba; only data from the reference formulation were used. Reba showed a relatively large inter-individual variability (from 2.6- to 3.3-fold) in the PK parameters with double peaks or the concentration plateau after the peak concentration in its serum concentration-time profiles. The population PKs of Reba was best described by a one-compartment model with three fraction absorption processes followed a single Weibull-type function and two first-order kinetics, and lag times. The study suggests that the efflux transporter MDR1 3435C>T allele affects the substantial inter-individual variability in the absorption of Reba according to genetic polymorphism. A significant difference was found in the absorption rate ka 1 among the MDR1 3435C>T genotype groups (P<0.05) (CT group, 79.8% increase; and TT group, 115% increase). The use of combined MDR1 3435C>T and body mass index as covariates for ka 1 exerted a more significant effect (P<0.05). In addition, body surface area significantly affected the apparent total clearance (P<0.05).

Successful Use of [14C]Paracetamol Microdosing to Elucidate Developmental Changes in Drug Metabolism

BackgroundWe previously showed the practical and ethical feasibility of using [14C]-microdosing for pharmacokinetic studies in children. We now aimed to show that this approach can be used to elucidate developmental changes in drug metabolism, more specifically, glucuronidation and sulfation, using [14C]paracetamol (AAP).MethodsInfants admitted to the intensive care unit received a single oral [14C]AAP microdose while receiving intravenous therapeutic AAP every 6 h. [14C]AAP pharmacokinetic parameters were estimated. [14C]AAP and metabolites were measured with accelerator mass spectrometry. The plasma area under the concentration-time curve from time zero to infinity and urinary recovery ratios were related to age as surrogate markers of metabolism.ResultsFifty children [median age 6 months (range 3 days–6.9 years)] received a microdose (3.3 [2.0–3.5] ng/kg; 64 [41–71] Bq/kg). Plasma [14C]AAP apparent total clearance was 0.4 (0.1–2.6) L/h/kg, apparent volume of distribution was 1.7 (0.9–8.2) L/kg, and the half-life was 2.8 (1–7) h. With increasing age, plasma and urinary AAP-glu/AAP and AAP-glu/AAP-sul ratios significantly increased by four fold, while the AAP-sul/AAP ratio significantly decreased.ConclusionUsing [14C]labeled microdosing, the effect of age on orally administered AAP metabolism was successfully elucidated in both plasma and urine. With minimal burden and risk, microdosing is attractive to study developmental changes in drug disposition in children.

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

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. The study was conducted in 12 hypertensive pregnant women [control group (CG)] and 10 hypertensive pregnant women with T2DM taking slow-release nifedipine (20mg, 12/12h). On the 34th week of gestation, serial blood samples were collected (0-12h) 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. The median pharmacokinetic parameters of CG were: peak plasma concentration (Cmax ) 26.41ngml-1 , time to reach Cmax (tmax ) 1.79h, area under the plasma concentration vs. time curve from 0-12h (AUC0-12 ) 235.99ng.hml-1 , half-life (t½) 4.34h, volume of distribution divided by bioavailability (Vd/F) 560.96l, and ClT /F 84.77lh-1 . The parameters for T2DM group were: Cmax 23.52ngml-1 , tmax 1.48h, AUC0-12 202.23ng.hml-1 , t½ 5.00h, Vd/F 609.40l, and apparent total clearance (ClT /F) 98.94lh-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. There was no influence of T2DM on the pharmacokinetics or placental transfer of nifedipine in hypertensive women with controlled diabetes.

Pediatric Patients With Solid or Hematological Tumor Disease: Vancomycin Population Pharmacokinetics and Dosage Optimization

In pediatric cancer patients, determination of optimal vancomycin dosage is essential because of high risk of inadequate concentrations and bacterial resistance. The aim of this study was to determine vancomycin pharmacokinetic parameters in this population and propose dosage optimization to achieve optimal concentration. We retrospectively reviewed the use of vancomycin in pediatric cancer patients with febrile neutropenia (hematological or solid tumor disease). Vancomycin was administered by continuous infusion, and dosages were adapted according to therapeutic drug monitoring results. Blood cultures were performed before the first dose of antibiotic. Vancomycin pharmacokinetic population parameters were determined using NONMEM software, and dosage simulations were performed according to the target concentration (20-25 mg/L). One hundred twenty-one patients were included in this study, representing 301 vancomycin concentrations. Blood cultures were positive in 37.5% of patients, and observed pathogens were mainly Staphylococcus spp. (43.8% methicillin resistant). Volume of distribution (95% confidence interval) was 34.7 L (17.3-48.0), and total apparent clearance (CL) (95% confidence interval) was correlated to body weight, tumor disease, and cyclosporine coadministration: CL = θCL × (WT/70) L/h with θCL = 3.49 (3.02-3.96), 4.66 (3.98-5.31), and 4.97 (4.42-5.41) in patients managed for hematological malignancies with or without cyclosporine coadministration and for solid malignancies, respectively. Based on simulation results, vancomycin dosage (milligram per kilogram) should be adapted to each child on the basis of its body weight and cyclosporine coadministration. Our results highlight the requirement to adapt vancomycin dosage in cancer pediatric population. Simulations have allowed to describe new dosage schedules, and a chart was created for clinicians to adapt vancomycin dosage.

Evaluation of Concomitant Antiretrovirals and CYP2C9/CYP2C19 Polymorphisms on the Pharmacokinetics of Etravirine.

Etravirine is a non-nucleoside reverse transcriptase inhibitor indicated in combination with other antiretrovirals for treatment-experienced HIV patients ≥6years of age. Etravirine is primarily metabolized by cytochrome P450 (CYP)2C9, CYP2C19, and CYP3A. This analysis determined the impact of concomitant antiretrovirals and CYP2C9/CYP2C19 phenotype on the pharmacokinetics of etravirine. We used 4728 plasma concentrations from 817 adult subjects collected from four clinical studies to develop the population pharmacokinetic model. The presence of atazanavir/ritonavir, lopinavir/ritonavir, darunavir/ritonavir, tenofovir disoproxil fumarate, or enfuvirtide together with the CYP2C9 and CYP2C19 phenotype and other demographics were evaluated. A one-compartment model with first-order input and a lag-time best described the data. Estimates of apparent total clearance (CL/F), apparent central volume of distribution (V c/F), first-order absorption rate constant (k a), and absorption lag-time were 41.7L/h, 972L, 1.16h, and 1.32h, respectively. Estimates of between-subject variability on CL/F, V c/F, and relative bioavailability (F) were 39.4%CV (percentage coefficient of variation), 35.9%CV and 35.5%CV, respectively. Between-occasion variability on F was estimated to be 30.0%CV. CL/F increased non-linearly with body weight and creatinine clearance (CLCR), and also varied based on CYP2C9/CYP2C19 phenotype. In this analysis, body weight, CLCR, and CYP2C9/CYP2C19 phenotype were found to describe some of the variability in CL/F. It was not possible to show an impact of concomitant antiretrovirals on the pharmacokinetics of etravirine for adults predominantly taking coadministered boosted protease inhibitors as a background antiretroviral regimen.

Effect of Moderate Hepatic Impairment on the Pharmacokinetics and Pharmacodynamics of Roxadustat, an Oral Hypoxia-Inducible Factor Prolyl Hydroxylase Inhibitor.

Background and ObjectiveRoxadustat is a hypoxia-inducible factor prolyl hydroxylase inhibitor in phase III development for the treatment of anaemia associated with chronic kidney disease. This study evaluated the effects of moderate hepatic impairment on roxadustat pharmacokinetics, pharmacodynamics and tolerability.MethodsThis was an open-label study in which eight subjects with moderate hepatic impairment (liver cirrhosis Child–Pugh score 7–9) and eight subjects with normal hepatic function (matched for body mass index, age and sex) received a single oral 100 mg roxadustat dose under fasted conditions. Blood samples were collected until 144 h post-dose in subjects with moderate hepatic impairment and until 96 h post-dose in subjects with normal hepatic function.ResultsIn subjects with moderate hepatic impairment, area under the concentration–time curve (AUC) from the time of drug administration to infinity (AUC∞) and observed maximum concentration (Cmax) were 23 % higher [geometric least-squares mean ratio (GMR) 123 %; 90 % CI 86.1–175] and 16 % lower (GMR 83.6 %; 90 % CI 67.5–104), respectively, than in subjects with normal hepatic function. Mean terminal half-life (t½) appeared to be longer (17.7 vs. 12.8 h) in subjects with moderate hepatic impairment, however intersubject variability on apparent total systemic clearance after single oral dosing (CL/F), apparent volume of distribution at equilibrium after oral administration (Vz/F) and t½ was approximately twofold higher. Erythropoietin (EPO) baseline-corrected AUC from administration to the last measurable EPO concentration (AUCE,last) and maximum effect (Emax) were 31 % (GMR 68.95 %; 90 % CI 29.29–162.29) and 48 % (GMR 52.29 %; 90 % CI 28.95–94.46) lower, respectively, than in subjects with normal hepatic function. The single oral roxadustat dose was generally well tolerated.ConclusionsThis study demonstrated the effect of moderate hepatic impairment on the pharmacokinetics and pharmacodynamics of roxadustat relative to subjects with normal hepatic function. These differences are not expected to be of clinical significance.

Impact of fraction unbound, CYP3A, and CYP2D6 in vivo activities, and other potential covariates to the clearance of tramadol enantiomers in patients with neuropathic pain.

The pharmacokinetics of tramadol is characterized by a large interindividual variability, which is partially attributed to polymorphic CYP2D6 metabolism. The contribution of CYP3A, CYP2B6, fraction unbound, and other potential covariates remains unknown. This study aimed to investigate the contribution of in vivo activities of cytochrome P450 (CYP) 2D6 and 3A as well as other potential covariates (CYP2B6 genotype to the SNP g.15631G>T, fraction unbound, age, body weight, creatinine clearance) to the enantioselective pharmacokinetics of tramadol. Thirty patients with neuropathic pain and phenotyped as CYP2D6 extensive metabolizers were treated with a single oral dose of 100 mg tramadol. Multiple linear regressions were performed to determine the contribution of CYP activities and other potential covariates to the clearance of tramadol enantiomers. The apparent total clearances were 44.9 (19.1-102-2) L/h and 55.2 (14.8-126.0) L/h for (+)- and (-)-tramadol, respectively [data presented as median (minimum-maximum)]. Between 79 and 83% of the overall variation in apparent clearance of tramadol enantiomers was explained by fraction unbound, CYP2D6, and CYP3A in vivo activities and body weight. Fraction unbound explained 47 and 41% of the variation in clearance of (+)-tramadol and (-)-tramadol, respectively. Individually, CYP2D6 and CYP3A activities were shown to have moderate contribution on clearance of tramadol enantiomers (11-16% and 11-18%, respectively). In conclusion, factors affecting fraction unbound of drugs (such as hyperglycemia or co-administration of drugs highly bound to plasma proteins) should be monitored, because this parameter dominates the elimination of tramadol enantiomers.

Population Pharmacokinetic Analysis of Lanreotide Autogel/Depot in the Treatment of Neuroendocrine Tumors: Pooled Analysis of Four Clinical Trials.

Lanreotide Autogel (lanreotide Depot in the USA) has demonstrated anti-tumor activity and control of the symptoms associated with hormone hypersecretion in patients with neuroendocrine tumors. The objectives of this study were to describe the pharmacokinetics of lanreotide Autogel administered 4-weekly by deep subcutaneous injections of 60, 90, or 120 mg in patients with gastroenteropancreatic neuroendocrine tumors (GEP-NETs), to quantify the magnitude of inter-patient variability (IPV), and to identify those patient characteristics that impact on pharmacokinetics. Analyses were based on pooled data from clinical trials. A total of 1541 serum concentrations from 290 patients were analyzed simultaneously by the population approach using NONMEM version 7.2. Covariates evaluated included demographics, renal and hepatic function markers, and disease-related parameters. Serum profiles were described by a one-compartment disposition model in which the absorption process was characterized by two parallel pathways following first- and zero-order kinetics. The estimated apparent volume of distribution was 18.3 L. The estimated apparent total serum clearance for a typical 74 kg patient was 513 L/day, representing a substantial difference in clearance in this population of patients with respect to healthy volunteers that could not be explained by any of the covariates tested. Body weight was the only covariate to show a statistically significant effect on the pharmacokinetic profile, but due to the overlap between the pharmacokinetic profiles of patients with lower or higher body weights the effect of body weight on clearance was not considered clinically relevant. The IPV was low for clearance (27%) and moderate to high for volume of distribution (150%) and the absorption constant (61%). Using two mechanisms of absorption, the pharmacokinetics of lanreotide Autogel were well-described in patients with GEP-NET. None of the patient characteristics tested were of clinical relevance to potential dose adjustment in clinical practice.