Stephen C. Harris

Mouse population-guided resequencing reveals that variants in CD44 contribute to acetaminophen-induced liver injury in humans

Interindividual variability in response to chemicals and drugs is a common regulatory concern. It is assumed that xenobiotic-induced adverse reactions have a strong genetic basis, but many mechanism-based investigations have not been successful in identifying susceptible individuals. While recent advances in pharmacogenetics of adverse drug reactions show promise, the small size of the populations susceptible to important adverse events limits the utility of whole-genome association studies conducted entirely in humans. We present a strategy to identify genetic polymorphisms that may underlie susceptibility to adverse drug reactions. First, in a cohort of healthy adults who received the maximum recommended dose of acetaminophen (4 g/d x 7 d), we confirm that about one third of subjects develop elevations in serum alanine aminotransferase, indicative of liver injury. To identify the genetic basis for this susceptibility, a panel of 36 inbred mouse strains was used to model genetic diversity. Mice were treated with 300 mg/kg or a range of additional acetaminophen doses, and the extent of liver injury was quantified. We then employed whole-genome association analysis and targeted sequencing to determine that polymorphisms in Ly86, Cd44, Cd59a, and Capn8 correlate strongly with liver injury and demonstrated that dose-curves vary with background. Finally, we demonstrated that variation in the orthologous human gene, CD44, is associated with susceptibility to acetaminophen in two independent cohorts. Our results indicate a role for CD44 in modulation of susceptibility to acetaminophen hepatotoxicity. These studies demonstrate that a diverse mouse population can be used to understand and predict adverse toxicity in heterogeneous human populations through guided resequencing.

Abuse potential, pharmacokinetics, pharmacodynamics, and safety of intranasally administered crushed oxycodone HCl abuse‐deterrent controlled‐release tablets in recreational opioid users

The objective of this study was to evaluate abuse potential, pharmacokinetics, pharmacodynamics, and safety of intranasally administered, crushed reformulated OxyContin® (oxycodone HCl controlled‐release) tablets (ORF), relative to crushed original OxyContin® (OC), oxycodone powder (Oxy API), and OC placebo. This randomized, double‐blind, positive‐ and placebo‐controlled crossover study enrolled healthy, adult, nonphysically dependent recreational opioid users with recent history of intranasal drug abuse (N = 27). Active treatments contained oxycodone (30 mg). Pharmacokinetics, pharmacodynamics (e.g., Overall Drug Liking [ODL], Take Drug Again [TDA], and High Visual Analog Scales [VAS]; Subjective Drug Value [SDV]; pupillometry; intranasal irritation), and safety (e.g., adverse events, vital signs, laboratory tests) were assessed to 24 hours postdose. Crushed ORF administration yielded reduced oxycodone Cmax and increased Tmax versus crushed OC and Oxy API. Peak effects for pharmacodynamic measures were delayed with ORF (1–2 hours) versus OC and Oxy API (0.5–1 hour). ODL, TDA, High VAS, and SDV Emax values were significantly lower (P ≤ .05) and some intranasal irritation ratings were greater for ORF versus OC and Oxy API. No significant or unexpected safety findings were observed. Compared with OC and Oxy API, intranasally administered ORF was associated with lower and delayed peak plasma concentrations, decreased drug‐liking, and decreased intranasal tolerability. This suggests that ORF has a decreased potential for intranasal oxycodone abuse. There were no significant or unexpected safety findings. As is true for all abuse potential studies, epidemiological or other appropriate post‐marketing studies are required to assess the impact of the reduction in intranasal oxycodone abuse potential observed in the present study on real‐world patterns of ORF misuse, abuse, and diversion.

Gender differences in pharmacokinetics and pharmacodynamics of zolpidem following sublingual administration

The effect of dose and gender on the pharmacokinetics (PK) and pharmacodynamics (PD) of zolpidem after administration of a buffered zolpidem sublingual tablet (ZST; Intermezzo®, Purdue Pharma L.P., Stamford, CT, USA) was evaluated in healthy non‐elderly male and female volunteers. Subjects received a single morning dose of ZST (1.0, 1.75, and 3.5 mg) or placebo in a four‐way crossover study. In male and female subjects zolpidem PK were linear, with area under the curve (AUC) proportional to dose, and apparent oral clearance and elimination half‐life independent of dose. However, AUC averaged 40% to 50% higher in females than in males receiving the same dose. The gender effect was incompletely explained by body weight. In females, ZST produced PD changes consistent with benzodiazepine agonist effects, particularly at the 3.5‐mg dose. For several PD variables, PD effects were significantly related to plasma zolpidem concentrations when data were aggregated across subjects. However, there was variability in response among individuals. In males, PD effects of zolpidem seldom differed from placebo regardless of plasma concentration. The findings confirm that zolpidem clearance is lower in females than in males. PD effects of zolpidem from ZST are greater in female subjects, due to a combination of higher plasma concentrations and greater intrinsic sensitivity.

Attractiveness of reformulated OxyContin® tablets: assessing comparative preferences and tampering potential

Reformulated OxyContin® (oxycodone HCl controlled-release or ORF) was developed as a tamper and abuse-deterrent product, to reduce the risk of product abuse, misuse and their consequences. This noninterventional single-session study asked participants who were medically-healthy recreational opioid users, aged 18 years and older, to consider how they would use commonly available supplies to tamper with placebo ORF and placebo original OxyContin (OC) tablets, and how they would assess the attractiveness of tampering and abusing ORF tablets, as compared with other opioid formulations. Participants provided information on past opioid use, and they assessed the properties of five nonhypothetical oxycodone products and two hypothetical oxycodone products. Participants provided feedback on tampering preferences, preferred tamper methods for each product, overall tampering potential and product preferences. We had 30 participants (27 males and 3 females; mean age 35 years, range 18–51) complete both the interview and tampering sessions. Participants judged OC as the most attractive, valuable, desirable and most likely to be tampered with, from among all opioid products studied. By contrast, they rated ORF as the least attractive, least valuable, least desirable, and least likely to be tampered with among all the nonhypothetical opioid products studied. These results suggested that recreational drug abusers view ORF tablets as tamper-deterrent products.

Effect of Ketoconazole on the Pharmacokinetic Profile of Buprenorphine following Administration of a Once-Weekly Buprenorphine Transdermal System

AbstractBackground and Objective: Buprenorphine is extensively metabolized by cytochrome P450 (CYP) 3A4. This study evaluated the effect of ketoconazole, a CYP3A4 inhibitor, on the metabolism of buprenorphine following the administration of a buprenorphine transdermal system 10μg/hour (BTDS 10). Methods: This single-centre study enrolled 20 healthy subjects who had demonstrated ketoconazole-mediated CYP3A4 inhibition via an erythromycin breath test. Subjects were randomized into a placebo-controlled, two-treatment, two-period crossover study. Subjects participated in a 7- to 14-day screening period, two baseline evaluations (day 0 [period 1] and day 16 [period 2]), two 12-day treatment periods (periods 1 and 2) separated by a 4-day washout period, and a study completion visit. Subjects received one BTDS 10 for 7 days per treatment period, administered concomitantly with either ketoconazole 200 mg twice daily or matching placebo. The main outcome measures were the ratios of geometric means for area under the plasma drug concentration versus time curve (AUC) from time zero to time of last measurable concentration (AUClast), AUC from time zero to infinity (AUC∞), and maximum plasma drug concentration (Cmax). Results: The ratio of geometric means (BTDS 10 with ketoconazole/BTDS 10 with placebo) was 99.4 (90% confidence interval [CI] 87.2, 113.3) for AUClast and 97.8 (90% CI 87.7, 109.1) for Cmax. The ratio of geometric means for AUC∞ was 86.7 (90% CI 70.7, 106.2). The plasma concentrations of the metabolites norbuprenorphine and norbuprenorphine-3β-glucuronide were slightly elevated following ketoconazole administration. BTDS 10 with ketoconazole was well tolerated and no apparent safety concerns were noted. Conclusion: The lack of a clinically significant CYP3A4 interaction with ketoconazole following transdermal delivery of buprenorphine is consistent with the parenteral administration of a high clearance drug bypassing exposure to gut wall and hepatic CYP3A4 first-pass effects. Metabolism of buprenorphine during therapy with BTDS is also not expected to be affected by co-administration of other CYP3A4 inhibitors.

Comparison of Pharmacokinetic Profiles of Zolpidem Buffered Sublingual Tablet and Zolpidem Oral Immediate-Release Tablet: Results from a Single-Center, Single-Dose, Randomized, Open-Label Crossover Study in Healthy Adults

BACKGROUND A zolpidem sublingual tablet (ZST) formulation was recently approved by the US Food and Drug Administration to treat middle-of-the-night (MOTN) awakening with difficulty returning to sleep. OBJECTIVE The aim of this study was to compare the zolpidem pharmacokinetic profiles of 3.5-mg ZST and 10-mg immediate-release (IR) oral zolpidem in healthy female and male adults. METHODS This randomized, open-label crossover study compared the pharmacokinetic profile of ZST with that of IR oral zolpidem in healthy adults. RESULTS The study enrolled 19 males and 14 females. After 3.5-mg ZST and 10-mg IR, respectively, mean zolpidem plasma concentrations at 15 minutes (22 vs 17 ng/mL, respectively, in females and 18 vs 10 ng/mL in males) and AUCs from zero to 15 minutes (2.3 vs 0.8 ng · h/mL in females and 1.6 vs 0.5 ng · h/mL in males) were substantially greater for ZST, despite the larger absolute IR dose. After 3.5-mg ZST and 10-mg IR, respectively, clearance was lower in females, even after correcting for body weight (2.63 vs 2.88 mL/min/kg in females and 3.63 vs 3.91 mL/min/kg in males). The lag time prior to the start of first-order absorption was notably shorter for ZST than IR in both males (8 vs 21 minutes) and females (5 vs 22 minutes). Both zolpidem formulations were generally well tolerated by both genders. CONCLUSIONS Systemic exposure of zolpidem was higher in females for both formulations. Plasma levels and AUC were higher, and clearance was lower, in females with both zolpidem formulations. The initial rate of absorption was faster, and initial systemic exposure was greater, with ZST compared with oral IR.

Clinical pharmacology and pharmacokinetics of once-daily hydromorphone hydrochloride extended-release capsules.

Hydromorphone hydrochloride extended release (HHER) is a multiparticulate melt‐extrusion pellet capsule formulation administered q24h. Study 1 investigated the bioavailability of 24‐mg HHER fed, as well as 24‐mg and 12‐mg HHER and 8‐mg hydromorphone hydrochloride immediate‐release (HHIR) tablets fasting. No clinically significant food effect was observed on hydromorphone Cmax or AUC for the 24‐mg HHER, and dose proportionality (AUC) was demonstrated between 12‐ and 24‐mg HHER. Study 2 demonstrated dose strength proportionality for 3 ± 12‐mg HHER versus 1 ± 32‐mg HHER. Study 3 evaluated 12‐mg HHER q24h versus 3‐mg HHIR q6h at steady state. HHER produced relatively constant steady‐state concentrations over 24 hours. HHER and HHIR were equivalent for AUCss. Cssmax was 26% lower for HHER than HHIR, Cssmin was 43% higher for HHER, and peak‐to‐trough fluctuation was 126% for HHER versus 328% for HHIR, which are ideal attributes of a once‐daily oral extended‐ release dosage form. HHER administration resulted in fewer adverse events than HHIR in study 3.

Once-Weekly Transdermal Buprenorphine Application Results in Sustained and Consistent Steady-State Plasma Levels

CONTEXT Transdermal formulations of buprenorphine offer controlled delivery of buprenorphine for sustained analgesic efficacy with reduced adverse events (AEs) compared with the other modes of administration. A buprenorphine transdermal system (BTDS) delivering 5, 10, or 20 mcg/hour for seven days is now marketed in the U.S. as Butrans(®) (Lohmann Therapie-System AG, Andernach Germany), a Schedule III single-entity opioid analgesic indicated for the management of moderate and chronic pain in patients requiring continuous around-the-clock analgesia for an extended period. OBJECTIVES This was a randomized open-label study in healthy subjects to characterize the steady-state buprenorphine pharmacokinetics after the delivery of three consecutive seven-day BTDS applications. METHODS Thirty-seven subjects were randomized to receive three consecutive BTDS 10 mcg/hour (BTDS 10) patches applied to the deltoid or upper back for seven days each. Blood samples for buprenorphine concentration measurements were taken. Safety was assessed using recorded AEs, clinical laboratory test results, vital signs, pulse oximetry, physical examinations, and electrocardiograms. Patch adhesion assessments were taken. RESULTS Analysis of Cmin demonstrated that steady state was reached during the first BTDS 10 application. No significant difference in Cmin was observed across the three applications. Total and peak plasma buprenorphine exposures were similar after each of the seven-day administrations of BTDS. CONCLUSION Three consecutive once-weekly applications of BTDS 10 provided consistent and sustained delivery of buprenorphine. Steady-state plasma concentrations were reached within 48 hours of the first application of BTDS 10. Patch adhesion analysis confirmed the appropriateness of the seven-day application period. Overall, BTDS 10 was safe and well tolerated.

Intranasal Abuse Potential, Pharmacokinetics, and Safety of Once-Daily, Single-Entity, Extended-Release Hydrocodone (HYD) in Recreational Opioid Users

Objectives. A once-daily, extended-release hydrocodone bitartrate tablet with abuse-deterrent properties (Hysingla ER® [HYD]) is available for the treatment of chronic pain in appropriate patients. This study evaluated the intranasal abuse potential and pharmacokinetics of HYD coarse and fine particles vs hydrocodone powder or placebo. Design. Single-center, double-blind, positive- and placebo-controlled, randomized, four-treatment crossover study. Subjects. Healthy adult, nondependent, recreational opioid users with a history of intranasal abuse. Methods. During four treatment periods, subjects (N = 31) received hydrocodone powder 60 mg, HYD coarse particles 60 mg, HYD fine particles 60 mg, or placebo, with five-to-seven-day washouts between treatments. Measures over 36 hours postdose included drug-liking and willingness to take drug again, assessed using visual analog scales (VASs), pupillometry, intranasal irritation, and pharmacokinetics. Results. Insufflation of both HYD coarse and fine particles led to lower “At this Moment” Drug Liking VAS peak values compared with hydrocodone powder, but higher values compared with placebo (P < 0.001 for all comparisons). Similar results were observed for Overall Drug Liking VAS, Take Drug Again VAS, and Subjective Drug Value. Compared with hydrocodone, insufflation of HYD particles led to reduced miosis and increased nasal irritation. Mean hydrocodone Cmax following insufflation of HYD coarse particles, HYD fine particles, and hydrocodone powder was 27.5, 36.5, and 105.8 ng/mL, respectively; median Tmax was ≥2-fold longer with either HYD particle size than hydrocodone powder; and (Cmax/Tmax) was 9.5, 13.4, and 82.0 ng/mL/h, respectively. Safety was consistent with that of opioid agonists. Conclusions. HYD demonstrated reduced intranasal abuse potential compared with hydrocodone powder.

Effects of buprenorphine on QT intervals in healthy subjects: results of 2 randomized positive- and placebo-controlled trials

ABSTRACT Objectives: To study the effect of transdermal buprenorphine on QTc prolongation at dose levels of 10, 40, and 80 mcg/h, (BTDS 10, BTDS 40, BTDS 80). Methods: Two randomized, placebo- and positive-controlled, parallel-group, dose-escalating clinical studies evaluated healthy adult subjects randomized to BTDS, placebo, or moxifloxacin in the first study; and to BTDS only, BTDS plus naltrexone, naltrexone alone at the same dose, placebo, or moxifloxacin in the second study. QT intervals were corrected for heart rate using data from each individual subject (QTcI). Results: In the first study (n = 44), the maximum upper bounds of the 90% confidence interval (CI) for mean placebo-corrected change from baseline in QTcI across 13 time points over 24 h were: 10.0 msec for BTDS 10 (Day 6) and 13.3 msec for BTDS 40 (Day 13); and 17.0 msec (Day 6) and 15.5 msec (Day 13) for moxifloxacin, respectively.  Similarly, in the second study (n = 66), the upper bound of the 90% CI for mean placebo-corrected change from baseline for QTcI was under 10 msec at all time points for BTDS 10 (maximum upper bound, 5.63 msec), over 10 msec at 5 time points for BTDS 40 (maximum 11.81 msec) and over 10 msec at all 13 time points for BTDS 80 (maximum, 14.14 msec). Naltrexone administered with BTDS eliminated the QTcI prolongation seen with supratherapeutic BTDS doses (BTDS 40, BTDS 80) administered without naltrexone. Conclusions: At the therapeutic dose of 10 mcg/h, BTDS has no clinically significant effect on QTc. At supratherapeutic doses of 40 and 80 mcg/h, BTDS treatment produces prolongation of QTcI similar in magnitude to that produced by a 400 mg dose of moxifloxacin. Despite the modest, dose-dependent increase in QTcI noted in these studies, transdermal buprenorphine has not been associated with proarrhythmic effects.