Midazolam Exposure Research Articles

Verification of a physiologically based pharmacokinetic model of ritonavir to estimate drug–drug interaction potential of CYP3A4 substrates

Ritonavir is one of several ketoconazole alternatives used to evaluate strong CYP3A4 inhibition potential in clinical drug-drug interaction (DDI) studies. In this study, four physiologically based pharmacokinetic (PBPK) models of ritonavir as an in vivo time-dependent inhibitor of CYP3A4 were created and verified for oral doses of 20, 50, 100 and 200mg using the fraction absorbed (Fa ) and oral clearance (CLoral ) values reported in the literature, because transporter and CYP enzyme reaction phenotyping data were not available. The models were used subsequently to predict and compare the magnitude of the AUC increase in nine reference DDI studies evaluating the effect of ritonavir at steady-state on midazolam (CYP3A4 substrate) exposure. Midazolam AUC and Cmax ratios were predicted within 2-fold of the respective observations in seven studies. Simulations of the hepatic and gut CYP3A4 abundance after multiple oral dosing of ritonavir indicated that a 3-day treatment with ritonavir 100mg twice daily is sufficient to reach maximal CYP3A4 inhibition and subsequent systemic exposure increase of a CYP3A4 substrate, resulting in the reliable estimation of fm,CYP3A4 . The ritonavir model was submitted as part of the new drug application for Kisqali® (ribociclib) and accepted by health authorities.

Curcumin as an In Vivo Selective Intestinal Breast Cancer Resistance Protein Inhibitor in Cynomolgus Monkeys

To estimate the clinical impact of pharmacokinetic modulation via breast cancer resistance protein (BCRP), in vivo approaches in nonclinical settings are desired in drug development. Clinical observation has identified curcumin as a promising candidate for in vivo selective BCRP inhibition, in addition to several well known inhibitors, such as lapatinib and pantoprazole. This study aimed to confirm the inhibitory efficacy of curcumin on gastrointestinal BCRP function in cynomolgus monkeys and to perform comparisons with lapatinib and pantoprazole. Oral area under the plasma concentration-time curve (AUC) and bioavailability of well known BCRP (sulfasalazine and rosuvastatin), P-glycoprotein (fexofenadine, aliskiren, and talinolol), and CYP3A (midazolam) substrates were investigated in the presence and absence of inhibitors. Oral exposures of sulfasalazine and rosuvastatin were markedly elevated by curcumin with minimal changes in systemic clearance, whereas pharmacokinetic alterations after fexofenadine, aliskiren, and talinolol oral exposure were limited. Curcumin increased oral midazolam exposure without affecting systemic clearance, presumably owing to partial inhibition of intestinal CYP3A. Lapatinib increased the oral AUC for sulfasalazine to a greater extent than curcumin did, whereas pantoprazole had a smaller effect. However, lapatinib also exerted significant effects on fexofenadine, failed to selectively discriminate between BCRP and P-glycoprotein inhibition, and had an effect on oral midazolam exposure comparable with that of curcumin. Thus, pharmacokinetic evaluation in monkeys demonstrated that pretreatment with curcumin as an in vivo selective BCRP inhibitor was more appropriate than pretreatment with lapatinib and pantoprazole for the assessment of the impact of BCRP on gastrointestinal absorption in nonrodent models.

Pretreatment with minocycline improves neurogenesis and behavior performance after midazolam exposure in neonatal rats.

Laboratory studies suggested that general anesthetics induce neuroapoptosis and inhibit neurogenesis in developing brains of animals. Minocycline exerts neuroprotection against a wide range of toxic insults in neurodegenerative diseases models. Here, we investigate whether minocycline can alleviate neurogenetic damage and improve cognition following midazolam exposure in neonatal rats. Postnatal 7 days rats were divided randomly into three groups: control group (C), midazolam group (M), and minocycline pretreatment group (MP). After exposure to midazolam, the cell proliferation in the subventricular zone (SVZ) and the subgranular zone (SGZ) of the hippocampus in pups was analyzed by bromodeoxyuridine immunochemistry at 7 days after the administration of anesthesia. Cognitive function was assessed using the Morris water-maze test at 35 days after midazolam exposure. Compared with the control, midazolam reduced cell proliferation both in the SVZ and in the SGZ of the hippocampus of neonatal rats, and decreased spatial learning and memory ability of rats in adulthood significantly. Pretreatment with minocycline increased cell proliferation both in the SVZ and in the SGZ of the hippocampus and improved spatial learning and memory ability compared with midazolam, but it did not mitigate the changes to the normal levels compared with the controls. Our results indicated that pretreatment with minocycline can alleviate midazolam-induced damage in neural stem cell proliferation of neonatal rats and improve spatial learning and memory ability of rats in adulthood.

Simultaneous Physiologically Based Pharmacokinetic (PBPK) Modeling of Parent and Active Metabolites to Investigate Complex CYP3A4 Drug-Drug Interaction Potential: A Case Example of Midostaurin.

Midostaurin (PKC412) is being investigated for the treatment of acute myeloid leukemia (AML) and advanced systemic mastocytosis (advSM). It is extensively metabolized by CYP3A4 to form two major active metabolites, CGP52421 and CGP62221. In vitro and clinical drug-drug interaction (DDI) studies indicated that midostaurin and its metabolites are substrates, reversible and time-dependent inhibitors, and inducers of CYP3A4. A simultaneous pharmacokinetic model of parent and active metabolites was initially developed by incorporating data from in vitro, preclinical, and clinical pharmacokinetic studies in healthy volunteers and in patients with AML or advSM. The model reasonably predicted changes in midostaurin exposure after single-dose administration with ketoconazole (a 5.8-fold predicted versus 6.1-fold observed increase) and rifampicin (90% predicted versus 94% observed reduction) as well as changes in midazolam exposure (1.0 predicted versus 1.2 observed ratio) after daily dosing of midostaurin for 4 days. The qualified model was then applied to predict the DDI effect with other CYP3A4 inhibitors or inducers and the DDI potential with midazolam under steady-state conditions. The simulated midazolam area under the curve ratio of 0.54 and an accompanying observed 1.9-fold increase in the CYP3A4 activity of biomarker 4β-hydroxycholesterol indicated a weak-to-moderate CYP3A4 induction by midostaurin and its metabolites at steady state in patients with advSM. In conclusion, a simultaneous parent-and-active-metabolite modeling approach allowed predictions under steady-state conditions that were not possible to achieve in healthy subjects. Furthermore, endogenous biomarker data enabled evaluation of the net effect of midostaurin and its metabolites on CYP3A4 activity at steady state and increased confidence in DDI predictions.

Physiologically Based Pharmacokinetic Model Predictions of Panobinostat (LBH589) as a Victim and Perpetrator of Drug-Drug Interactions.

Panobinostat (Farydak) is an orally active hydroxamic acid-derived histone deacetylase inhibitor used for the treatment of relapsed or refractory multiple myeloma. Based on recombinant cytochrome P450 (P450) kinetic analyses in vitro, panobinostat oxidative metabolism in human liver microsomes was mediated primarily by CYP3A4 with lower contributions by CYP2D6 and CYP2C19. Panobinostat was also an in vitro reversible and time-dependent inhibitor of CYP3A4/5 and a reversible inhibitor of CYP2D6 and CYP2C19. Based on a previous clinical drug-drug interaction study with ketoconazole (KTZ), the contribution of CYP3A4 in vivo was estimated to be ∼40%. Using clinical pharmacokinetic (PK) data from several trials, including the KTZ drug-drug interaction (DDI) study, a physiologically based pharmacokinetic (PBPK) model was built to predict panobinostat PK after single and multiple doses (within 2-fold of observed values for most trials) and the clinical DDI with KTZ (predicted and observed area under the curve ratios of 1.8). The model was then applied to predict the drug interaction with the strong CYP3A4 inducer rifampin (RIF) and the sensitive CYP3A4 substrate midazolam (MDZ) in lieu of clinical trials. Panobinostat exposure was predicted to decrease in the presence of RIF (65%) and inconsequentially increase MDZ exposure (4%). Additionally, PBPK modeling was used to examine the effects of stomach pH on the absorption of panobinostat in humans and determined that absorption of panobinostat is not expected to be affected by increases in stomach pH. The results from these studies were incorporated into the Food and Drug Administration-approved product label, providing guidance for panobinostat dosing recommendations when it is combined with other drugs.

Repeated administration of Sailuotong, a fixed combination of Panax ginseng, Ginkgo biloba, and Crocus sativus extracts for vascular dementia, alters CYP450 activities in rats

BackgroundSailuotong (SLT) is a standard Chinese preparation made from extracts of Panax ginseng (ginseng), Ginkgo biloba (ginkgo), and Crocus sativus (saffron). Preliminary clinical trials and animal experiments have demonstrated that SLT could improve cognition of vascular dementia (VD). PurposeTo avoid incident drug-drug interaction which is easily encountered in patients of VD, the potential influence of SLT on main drug-metabolic cytochromes P450 enzymes (CYP450) was investigated. MethodA “cocktail probes” approach was employed to evaluate the activities of CYP450. A rapid and selective analysis method was developed to examine 5 CYP probe drugs and their specific metabolites in plasma by using online SPE followed by a single LC-MS/MS run. After pretreatment for 2 weeks with SLT, ginseng, gingko, saffron or water (control), a cocktail solution containing caffeine, losartan, omeprazole, dextromethorphan and midazolam was given to rats orally. The plasma was obtained at different time intervals and then measured for the concentration of probes and their metabolites using developed SPE-LC-MS/MS method. Activity of five isozymes was estimated by comparing plasma pharmacokinetics of substrates and their metabolites (caffeine/paraxanthine for CYP1A2, losartan/E-3174 for CYP2C11, omeprazole/5-hydroxyl omeprazole for CYP2C6, dextromethorphan/dextrophan for CYP2D2 and midazolam/1-hydroxyl midazolam for CYP3A1/2) between control and drug treatment groups. ResultCompared with control group, repeated administration of SLT induced CYP1A2 by enhancing AUC paraxanthine / AUC caffeine to144%. The influence is attributed to its herbal component of ginseng to a large extent. Meanwhile, metabolic ability towards losartan was significantly elevated in SLT and gingko group by 31% and 25% respectively, indicating weak induction of CYP2C11 in rats. The analysis on probes of omeprazole and dextromethorphan showed a lack of influence on CYP 2C6 and CYP2D2 in all treated groups. In terms of CYP3A1/2, SLT decreased AUC ratio of 1-hydroxyl midazolam to midazolam by 39% and extended the half-life of midazolam apparently. Besides, significantly decreased systematic exposure of midazolam suggested the inhibition on metabolism of CYP3A1/2 is likely secondary to the interaction on absorption at intestinal level. The inhibition of SLT on CYP3A was likely attributed to ginseng and gingko cooperatively. ConclusionFurther observation on herb-drug interaction should be considered during clinical application of SLT.

Compelling Relationship of CYP3A Induction to Levels of the Putative Biomarker 4β-Hydroxycholesterol and Changes in Midazolam Exposure.

No abstract is required for this type of manuscript. But the following describes the overall intent of this work. This is a commentary manuscript for your consideration for publication. This work describes our observations of a compelling relationship between the increase in the putative CYP3A plasma biomarker, 4-beta-hydroxycholesterol (4BHC), and the corresponding decrease in midazolam exposure (a sensitive CYP3A substrate) as a result of clinical CYP3A induction by rifampicin (RIF), including dose-response aspects. The results discussed include those from the literature and our own internal data. To our knowledge, this composite view (which we term an “Emax-Imax” model) has not been explicitly described by others. It is our hope that other researchers will elaborate on this observation/model and thereby help to better define the use of 4HC in the study of clinical variability and DDI.

Midazolam dose correlates with abnormal hippocampal growth and neurodevelopmental outcome in preterm infants.

Very preterm-born neonates (24-32 weeks of gestation) are exposed to stressful and painful procedures during neonatal intensive care. Analgesic and sedation therapies are essential, and opiates and benzodiazepines are commonly used. These medications may negatively impact brain development. The hippocampus may be especially vulnerable to the effects of pain and analgesic and/or sedative therapies and contribute to adverse outcomes. The effect of invasive procedures and analgesic-sedative exposure on hippocampal growth was assessed, as was that of hippocampal growth on neurodevelopmental outcome. A total of 138 neonates (51% male, median gestational age = 27.7 weeks) underwent magnetic resonance imaging and diffusion tensor imaging (DTI) scans, early in life (postmenstrual age [PMA] = 32.3 weeks) and at term-equivalent age (PMA = 40.2 weeks). Volumes and DTI measures of axial diffusivity, radial diffusivity, and mean diffusivity (MD) were obtained from the hippocampus. Cognitive, language, and motor abilities were assessed using the Bayley Scales of Infant Development-III at 18.7 months median corrected age. Models testing the association of invasive procedures with hippocampal volumes and DTI measures accounted for birth gestational age, sex, PMA, dose of analgesics/sedatives (fentanyl, morphine, midazolam), mechanical ventilation, hypotension, and surgeries. Total midazolam dose predicted decreased hippocampal volumes (β = -1.8, p < 0.001) and increased MD (β = 0.002, p = 0.02), whereas invasive procedures did not (β = 0, p > 0.5 each). Lower cognitive scores were associated with hippocampal growth (β = -0.31, p = 0.003), midazolam dose (β = -0.27, p = 0.03), and surgery (β = -8.32, p = 0.04). Midazolam exposure was associated with macro- and microstructural alterations in hippocampal development and poorer outcomes consistent with hippocampal dysmaturation. Use of midazolam in preterm neonates, particularly those not undergoing surgery, is cautioned.

The Influence of Single-Dose and Short-Term Administration of Quercetin on the Pharmacokinetics of Midazolam in Humans

Quercetin is a plant flavonol that is available from both daily diet and nutraceuticals. To investigate the effect of acute and short-term intake of high-dose quercetin on CYP3A-mediated metabolism, 10 healthy volunteers received 7.5 mg oral midazolam without, with a single dose of 1500 mg quercetin and after 1-week supplementation with 1500 mg quercetin daily. A substudy was performed in three subjects to explore the impact of repeated quercetin intake on intravenously administered midazolam. Coadministration with a single dose of quercetin did not significantly alter the pharmacokinetics of midazolam and its 1'-hydroxymetabolite, but following short-term quercetin intake, there was a trend to reduced midazolam exposure (geometric mean ratio of test-control area under the plasma concentration-time curve (AUC0-∞ ): 0.82; 90% confidence interval: 0.61-1.10) and midazolam-metabolite AUC0-∞ ratios were decreased by 9.7%-47.6% from control in seven subjects. The tendency was opposite when midazolam was given intravenously. We conclude that a single dose of quercetin would not provoke any toxic adverse events when coadministered with midazolam, whereas repeated quercetin intake can reduce systemic exposure to the orally given drug by increasing its CYP3A-catalyzed metabolism. As the effect deviated after intravenous drug administration, different mechanisms of interaction may be involved at the intestinal site compared with the liver.

Developmental stage-dependent impact of midazolam on calbindin, calretinin and parvalbumin expression in the immature rat medial prefrontal cortex during the brain growth spurt

BackgroundHuman epidemiological data suggest a link between anesthesia exposure in early postnatal life and subsequent lasting neurocognitive alterations. Understanding the underlying mechanisms of this potential association is of paramount importance in an attempt to develop protective strategies. While general anesthetics are powerful modulators of GABAergic neurotransmission, little is known about the impact of these drugs on developing GABAergic networks. Here we addressed this issue by evaluating the impact of a 6-h-long midazolam exposure on the development of calbindin-, calretinin- and parvalbumin-expressing GABAergic interneurons. MethodsPhysiological expression patterns of calbindin-, calretinin-, and parvalbumin-positive neurons as well as the impact of a 6-h-long midazolam exposure on these cell populations were evaluated in the medial prefrontal cortex of Wistar rats at defined stages of the brain growth spurt using stereological analysis. Activated caspase-3 immunohistochemistry was used to quantify apoptotic death in controls and midazolam-treated subjects. ResultsIn control animals, the number of parvalbumin expressing cells significantly (p<0.01) increased while those of calbindin positive populations significantly (p<0.01) decreased between postnatal day 10 and 20. Expression of calretinin remained constant during this period. Immediately following exposure, midazolam induced neuroapoptosis at both early (postnatal day 5, p=0.016) and later (postnatal day 15, p=0.025) stages of brain development. While this did not diminish overall neuronal density in the medial prefrontal cortex, exposure at P5 led to a subsequent increase in the number of parvalbumin positive neurons in lower cortical layers, and midazolam administration at P15 increased the number of both parvalbumin and calretinin expressing neurons 5 days following exposure. ConclusionThese observations demonstrate that midazolam exposure can impair the physiological differentiation patterns of GABAergic interneurons during the brain growth spurt. Considering the important role of GABAergic networks in neuronal physiology, these data provide us with one potential mechanism that could account for the lasting neurobehavioral and cognitive deficits observed in the context of anesthesia exposure in the early postnatal period.

In vitro evaluation of Schisandra extracts (SE) herb-drug interaction potential utilizing B-Clear® sandwich-culture human hepatocytes (SCHH)

Herb-drug interaction (HDI) potential should be evaluated given the dramatic increase in the sale and use of alternative medicines. A fully integrated hepatic cell system that includes drug metabolism, drug transport, and key regulatory pathways was utilized to assess SE HDI potential. We investigated SE for hepatocyte cytotoxicity using ATP and LDH assays following 24 or 72 hrs exposure. After 24 hrs exposure with S. chinensis extract (SCE) or S. sphenanthera extract (SSE), no marked changes were observed in either assay at the concentrations examined. However, ATP pools were modestly reduced in hepatocytes following 72 hrs of exposure at the highest concentrations. Next, we examined the SE potential to inhibit CYP3A4/5 enzyme activity and P-gP function in our system. Significant inhibition of OH-midazolam formation was observed in SCHH by SCE (IC50 = 4.4 µg/mL) and SPE (IC50 = 0.8 µg/mL). Pre-incubation of SCE in SCHH prior to midazolam exposure yielded a 3-fold decrease in the CYP3A4/5 IC50 providing evidence of time-dependent inhibition; an effect not observed with SPE. Significant inhibition of digoxin efflux was observed with increasing concentrations of both SE, reducing the digoxin hepatobiliary clearance significantly. Finally, we examined the potential of SE to modulate the expression of P450 or drug transporter proteins in SCHH following 72 hr of exposure to SCE or SPE. St. John's Wort (20 µg/mL), a positive control inducer, induced CYP2B6 and CYP3A4 mRNA and enzyme activity demonstrating that key regulatory pathways in SCHH were functional. Changes were observed in gene expression and functional assays in response to SE. Our results of SPE inhibition of CYP3A4/5 and P-gP are consistent with clinical data that demonstrated significant SPE drug interactions resulting in > 60% increase in AUC of tacrolimus. In summary, in vitro results demonstrated that SCE and SPE both had similar inhibition profiles of CYP3A4/5 and P-gP but SCE has a higher potential to cause clinically relevant HDIs as compared to the SPE varietal because of time-dependent inhibition.

Pharmacokinetic interaction of intravenous fentanyl with ketoconazole.

Fentanyl is primarily metabolized by CYP3A, but has also been suggested to act as a weak inhibitor of CYP3A. We investigated the influence of CYP3A inhibition by ketoconazole on the pharmacokinetics of intravenously administered fentanyl and the effect of fentanyl on CYP3A activity. A prospective, open-label, randomized, monocentre, crossover study was conducted in 16 healthy volunteers. They received fentanyl alone (5 microgram per kilogram) or fentanyl plus ketoconazole (200 milligram orally B.I.D. over 2 days). Naloxone (2 × 0.2 milligram i.v.) was given simultaneously with fentanyl to mitigate any opioid effect. Midazolam was administered as a CYP3A probe drug. Fentanyl and its metabolites were quantified by LC/MS/MS in blood and urine samples obtained over 24 hour. Exposure of fentanyl (AUC0- ∞ ) was significantly increased to 133% and systemic clearance was reduced to 78% by ketoconazole, norfentanyl formation was significantly delayed and partial metabolic clearance decreased to 18%. Fentanyl had no influence on midazolam exposure and CYP3A activity whereas ketoconazole decreased CYP3A activity to 13%. Although fentanyl N-dealkylation is substantially inhibited by ketoconazole, exposure of fentanyl itself increased by one third only. Clinically fentanyl dosage adjustments may become necessary when ketoconazole or other strong CYP3A inhibitors are given simultaneously. Fentanyl itself does not influence CYP3A activity.

A comparison of the metabolism of midazolam in C57BL/6J and hepatic reductase null (HRN) mice

The hepatic cytochrome P450 reductase null (HRN) mouse, which has no functional hepatic Cyp P450s, may represent a useful model for examining extra-hepatic P450-related oxidative metabolism. Here the pharmacokinetics and metabolic fate of midazolam, a drug known to undergo such extra-hepatic metabolism, have been investigated in the HRN mouse and compared with a phenotypically normal strain (C57BL/6J). In addition, the effects of co-administration of the pan-P450 inhibitor 1′-aminobenzotriazole (ABT) on the metabolic profile have been compared in both strains. Significant pharmacokinetic differences for midazolam were observed between the two strains of mice with the HRN mice showing lower circulating concentrations of 1′-hydroxymidazolam but higher concentrations of 1′-hydroxymidazolam-O-glucuronide. A significant increase in midazolam exposure was seen upon ABT exposure for both strains of mice, but no differences in the area under the concentration time curves (AUC) for the monitored metabolites were observed. Although oxidative metabolism of midazolam was not abolished, significant decreases in 1′-hydroxymidazolam formation ratios were observed for both strains of mice exposed to ABT. Metabolite profiling of blood and bile showed a number of qualitative and quantitative differences between HRN and normal mice. These differences in midazolam metabolism between the two strains of mice clearly demonstrate the role that liver P450 enzymes play in the murine metabolism of midazolam. The fate of the compound in the HRN mice shows the importance of extrahepatic metabolism and also showed that these mice appear to be more capable of forming circulating phase II glucuronides than the normal strain.

Pharmacokinetic Evaluations of the Co-Administrations of Vandetanib and Metformin, Digoxin, Midazolam, Omeprazole or Ranitidine

Vandetanib is a selective inhibitor of vascular endothelial growth factor receptor (VEGFR), epidermal growth factor receptor (EGFR) and rearranged during transfection (RET) signalling, indicated for the treatment of medullary thyroid cancer. We investigated potential drug-drug interactions between vandetanib and metformin [organic cation transporter 2 (OCT2) substrate; NCT01551615]; digoxin [P-glycoprotein (P-gp) substrate; NCT01561781]; midazolam [cytochrome P450 (CYP) 3A4 substrate; NCT01544140]; omeprazole (proton pump inhibitor) or ranitidine (histamine H2-receptor antagonist; both NCT01539655). Four open-label, phase I studies were conducted in healthy volunteers: n=14 (metformin), n=14 (digoxin), n=17 (midazolam), n=16 (omeprazole), n=18 (ranitidine). Three of these comprised the following regimens: metformin 1000mg±vandetanib 800mg, midazolam 7.5mg±vandetanib 800mg, or digoxin 0.25mg±vandetanib 300mg. The randomized study comprised vandetanib 300mg alone and then either (i) omeprazole 40mg (days 1-4), and omeprazole+vandetanib (day 5); or (ii) ranitidine 150mg (day 1), and ranitidine+vandetanib (day 2). The primary objective assessed metformin, digoxin, midazolam and vandetanib pharmacokinetics. Vandetanib+metformin increased metformin area under the plasma concentration-time curve from zero to infinity (AUC0-∞) and maximum observed plasma concentration (Cmax) by 74 and 50%, respectively, and decreased the geometric mean metformin renal clearance (CLR) by 52% versus metformin alone. Vandetanib+digoxin increased digoxin area under the concentration-time curve from zero to the last quantifiable concentration (AUC0-last) and Cmax by 23 and 29%, respectively, versus digoxin alone, with only a 9% decrease in CLR. Vandetanib had no effect on midazolam exposure. Vandetanib exposure was unchanged during co-administration with omeprazole/ranitidine. Treatment combinations were generally well tolerated. Patients receiving vandetanib with metformin/digoxin may require additional monitoring of metformin/digoxin, with dose adjustments where necessary. Vandetanib with CYP3A4 substrates or omeprazole/ranitidine is unlikely to result in clinically relevant drug-drug interactions.

Effect of erlotinib on CYP3A activity, evaluated in vitro and by dual probes in patients with cancer

In vitro, erlotinib (0-30 µmol/l) and C-labelled midazolam (MDZ) (5 µmol/l) were incubated with human liver microsomes; separately, microsomes were preincubated with erlotinib (10 µmol/l) before the addition of MDZ. Results showed a time-dependent inhibition of MDZ metabolism by erlotinib, with a Ki of 7.5 µmol/l and an inactivation rate constant of 0.009/min. Patients with cancer (n=24) received a single oral dose of 7.5 mg MDZ and a single intravenous dose of 3 µCi [C-N-methyl] erythromycin on days 1, 8, 14 and 21. Patients also received 150 mg oral erlotinib daily from day 8 to day 14. Plasma concentrations of erlotinib and OSI-420 were determined on days 8 and 14; MDZ and 1'-hydroxymidazolam were determined on days 1, 8, 14 and 21. Coadministration of erlotinib resulted in a 4 and a 16% increase in CO2 on days 8 and 14, respectively, after the administration of erythromycin. The mean AUC0-last of MDZ decreased 17 and 34% after erlotinib treatment on day 8 and day 14, respectively. The half-life of MDZ and the AUC ratio of 1'-hydroxymidazolam to MDZ were not significantly changed. Although erlotinib may be a weak mechanism-based irreversible inhibitor of CYP3A4 in vitro, in vivo, erlotinib did not inhibit CYP3A-mediated metabolism, as determined by the erythromycin breath test and the MDZ pharmacokinetics. The mechanism for reduced exposure of MDZ is unclear, but may be because of an increase in intestinal metabolism or decreased absorption. These findings suggest that coadministration of erlotinib may not result in clinically relevant increases in exposure of CYP3A substrates.

The addition of tramadol to the standard of i.v. acetaminophen and morphine infusion for postoperative analgesia in neonates offers no clinical benefit: a randomized placebo-controlled trial.

Tramadol is used following neonatal cardiac and general surgery. However, its ability to opioid-spare or facilitate earlier extubation in postoperative neonates is unquantified. This randomized placebo-controlled trial aimed to assess whether tramadol's addition to standard analgesia resulted in earlier extubation or reduced analgesic/sedative requirements in postsurgical neonates. Neonates born ≥32 weeks postmenstrual age received either tramadol [T] 2 mg·kg(-1) or placebo [P] 6-hourly for up to 5 days postthoracoabdominal surgery in addition to morphine (commenced at 20 mcg·kg(-1) ·h(-1)) and 6-hourly i.v. acetaminophen. Time to extubation, morphine and midazolam amounts, hourly pain scores, and seizure activity were compared using an intention-to-treat and per-protocol analysis. Seventy-one neonates participated. Median survival time to extubation was similar between the groups (T 67 h [95% CI 51, 84] vs P 52 h [95%CI 43, 65]; P = 0.4), and similar numbers were extubated by 96 h (T 69% vs P 77%; difference -8%, 95%CI -28, 13%). Morphine and midazolam exposure was similar, with low pain scores in both groups (mean percentage of time with a pain score >5/20 during the 5 days: T 13% vs P 11%, difference in means 2.8 [95% CI -1.8, 7.6], P = 0.20). Most participants had normal cranial ultrasounds (T 86% vs P 86%); no seizures occurred clinically or electroencephalographically. Tramadol's addition to standard analgesia in this small group of postsurgical neonates did not appear to have any positive effect on time to extubation, morphine or midazolam exposure, or pain scores. This questions the benefit of tramadol for postsurgical neonates. Importantly, no seizures occurred in these ill neonates who may potentially be at greater risk of tramadol toxicity compared with adults.

THU0135 Evaluation of Drug-Drug Interactions of VX-509 (DECERNOTINIB), an Oral Selective Janus Kinase 3 Inhibitor, in Healthy Human Volunteers

BackgroundPatients with rheumatoid arthritis (RA) often receive multiple medications to manage the signs and symptom of comorbidities. It is therefore important to understand the potential for drug-drug interactions (DDI). VX-509...

Evaluation of 4β-Hydroxycholesterol as a Clinical Biomarker of CYP3A4 Drug Interactions Using a Bayesian Mechanism-Based Pharmacometric Model.

A Bayesian mechanism–based pharmacokinetic/pharmacodynamic model of cytochrome P450 3A4 (CYP3A4) activity was developed based on a clinical study of the effects of ketoconazole and rifampin on midazolam exposure and plasma 4β-hydroxycholesterol (4βHC) concentrations. Simulations from the model demonstrated that the dynamic range of 4βHC as a biomarker of CYP3A4 induction or inhibition was narrower than that of midazolam; an inhibitor that increases midazolam area under the curve by 20-fold may only result in a 20% decrease in 4βHC after 14 days of dosing. Likewise, an inducer that elevates CYP3A4 activity by 1.2-fold would reduce the area under the curve of midazolam by 50% but would only increase 4βHC levels by 20% after 14 days of dosing. Elevation in 4βHC could be reliably detected with a twofold induction in CYP3A4 activity with study sample sizes (N ~ 6–20) typically used in early clinical development. Only a strong CYP3A4 inhibitor (e.g., ketoconazole) could be detected with similar sample sizes.

Cytochrome P450 3A and P-glycoprotein drug-drug interactions with voclosporin

Voclosporin is a novel calcineurin inhibitor intended for prevention of organ graft rejection and treatment of lupus nephritis. Pharmacokinetic drug interactions between voclosporin and a CYP3A inhibitor, inducer and substrate and a P-glycoprotein inhibitor and substrate were evaluated. Voclosporin 0.4 mg kg(-1) was administered to 24 subjects in each of five studies, as follows: every 12 h (Q12H) alone and concomitantly with ketoconazole 400 mg once daily (QD); single dose before and single dose after rifampin 600 mg QD; Q12H where midazolam 7.5 mg was administered as a single dose alone before voclosporin and with last the dose of voclosporin; Q12H alone and concomitantly with verapamil 80 mg every 8 h; and Q12H with digoxin 0.25 mg QD. The noncompartmental pharmacokinetic parameters maximal concentration (Cmax ) and area under the concentration-time curve (AUC) were obtained, and geometric least squares mean ratios and 90% confidence intervals were evaluated. Ketoconazole increased voclosporin Cmax (6.4-fold) and AUC (18-fold); rifampin reduced voclosporin AUC (0.9-fold); voclosporin did not change exposure of midazolam or α-hydroxy-midazolam; verapamil increased voclosporin Cmax (2.1-fold) and AUC (2.7-fold); and voclosporin increased digoxin Cmax (0.5-fold), AUC (0.25-fold) and urinary excretion (0.2-fold). Administration of voclosporin concomitantly with strong inhibitors and inducers of CYP3A resulted in increased and decreased exposures, respectively, and should be considered contraindicated. Drug-drug interactions involving voclosporin and CYP3A substrates are not expected. Administration of voclosporin concomitantly with inhibitors and substrates of P-glycoprotein resulted in increased voclosporin and substrate exposures, respectively. Appropriate concentration and safety monitoring is recommended with co-administration of voclosporin and P-glycoprotein substrates and inhibitors.

1-Aminobenzotriazole Modulates Oral Drug Pharmacokinetics through Cytochrome P450 Inhibition and Delay of Gastric Emptying in Rats

The simultaneous effects of the cytochrome P450 inhibitor 1-aminobenzotriazole (ABT) on inhibition of in vivo metabolism and gastric emptying were evaluated with the test compound 7-(3,5-dimethyl-1H-1,2,4-triazol-1-yl)-3-(4-methoxy-2-methylphenyl)-2,6-dimethylpyrazolo[5,1-b]oxazole(NVS-CRF38), a novel corticotropin releasing factor receptor 1 (CRF1) antagonist with low water solubility, and the reference compound midazolam with high water solubility in rats. Pretreatment of rats with 100 mg/kg oral ABT administered 2 hours before a semisolid caloric test meal markedly delayed gastric emptying. ABT increased stomach weights by 2-fold; this is likely attributable to a prosecretory effect because stomach concentrations of bilirubin were comparable in ABT and control groups. ABT administration decreased the initial systemic exposure of orally administered NVS-CRF38 and increased Tmax 40-fold, suggesting gastric retention and delayed oral absorption. ABT increased the initial systemic exposure of midazolam, however for orally (but not subcutaneously) administered midazolam, extensive variability in plasma-concentration time profiles was apparent. Careful selection of administration routes is recommended for ABT use in vivo, variable oral absorption of coadministered compounds can be expected due to a disturbance of gastrointestinal transit.