Assessment of a formulation designed to be crush-resistant in prescription opioid abusers.

BACKGROUND: The extent of prescription opioid abuse has led to the development of formulations that are difficult to crush. The purpose of the present studies was to examine whether experienced prescription opioid abusers (individuals using prescription opioids for non-medical purposes regardless of how they were obtained) were able to prepare a formulation of oxymorphone hydrochloride ER 40 mg designed to be crush-resistant (DCR) for intranasal (study 1) or intravenous abuse (study 2), utilizing a non-crush-resistant formulation of oxymorphone (40 mg; OXM) as a positive control. METHODS: No drug was administered in these studies. Participants were provided with DCR and OXM tablets in random order and asked to prepare them for abuse with tools/solutions that they had previously requested. The primary outcome for study 1 was particle size distribution, and the primary outcome for study 2 was percent yield of active drug in the extracts. Other descriptive variables were examined to better understand potential responses to these formulations. RESULTS: Fewer DCR than OXM particles were smaller than 1.705 mm (9.8% vs. 97.7%), and thus appropriate for analyses. Percent yield of active drug in extract was low and did not differ between the two formulations (DCR: 1.95%; OXM: 1.29%). Most participants were not willing to snort (92%) or inject (84%) the tampered products. Participants indicated that they found less relative value in the DCR than the OXM formulation across both studies. CONCLUSIONS: These data suggest that the oxymorphone DCR formulations may be a promising technology for reducing opioid abuse.

The effects of ethanol on the bioavailability of oxymorphone extended-release tablets and oxymorphone crush-resistant extended-release tablets.

UNLABELLED: Adverse events may occur with an extended-release (ER) opioid if tampering or coadministration with ethanol causes excessive exposure (dose dumping) to the opioid. The effects of ethanol on the in vitro dissolution and in vivo pharmacokinetics of oxymorphone ER and oxymorphone crush-resistant formulation (CRF) were evaluated. In vitro dissolution rates were measured for oxymorphone ER 40-mg and oxymorphone CRF 40-mg tablets in aqueous solutions of 0 to 40% ethanol. In 2 in vivo, open-label, randomized, crossover studies, fasted healthy volunteers received single oral doses of oxymorphone ER 40 mg or oxymorphone CRF 40 mg with 240 mL of 0 to 40% ethanol. Naltrexone was used to minimize opioid effects. In the in vitro analyses, dissolution rates of oxymorphone ER and CRF were unaffected in aqueous solutions of ≤40% ethanol. Coadministration of oxymorphone ER or oxymorphone CRF with ethanol 20 and 40% increased oxymorphone peak plasma concentrations (C(max)) by 14 to 80% and reduced time to C(max). For both formulations, oxymorphone area under the curve and terminal half-life were largely unaffected, but C(max) increased with ethanol dose. Neither oxymorphone formulation exhibited dose dumping in terms of overall exposure when coingested with ethanol. PERSPECTIVE: Administering oxymorphone ER or oxymorphone CRF with 240 mL of ≤40% ethanol increased oxymorphone C(max) without dose dumping in terms of area under the curve. These results provide reassurance about the integrity of oxymorphone ER formulations with ethanol. Nonetheless, alcohol and opioids should never be combined because of the risk of respiratory depression.

Bioequivalence of oxymorphone extended release and crush-resistant oxymorphone extended release.

BACKGROUND: A formulation of crush-resistant extended-release opioids may deter abuse. The purpose of this study was to evaluate the bioequivalence of oxymorphone extended-release (Oxy-ER) and a crush-resistant formulation of oxymorphone extended-release (Oxy-CRF). METHODS: In three open-label, randomized studies, healthy adults at a clinical research center received two single oral doses of Oxy-ER and two single doses of Oxy-CRF, each separated by a ≥7-day washout. Doses were administered under fasted conditions (study 1, 5 mg doses; study 2, 40 mg doses) or after a high-fat breakfast (study 3, 40 mg doses). Subjects administered 40 mg doses also received naltrexone. The primary endpoint was systemic oxymorphone exposure; the bioequivalence criterion was met if the 90% confidence intervals of the geometric mean ratio (Oxy-CRF/Oxy-ER) for oxymorphone area under the curve from time 0 to the last measured concentration (AUC(0-t)), AUC from time 0 to infinity (AUC(0-inf)), and maximum plasma concentration (C(max)) were within 0.8-1.25. Safety was assessed by monitoring adverse events. RESULTS: In studies 1, 2, and 3, the safety population comprised 30, 37, and 36 subjects and the pharmacokinetics population comprised 27, 30, and 29 subjects, respectively. Oxy-ER and Oxy-CRF produced similar mean ± standard deviation oxymorphone AUC(0-t) (study 1, 5.05 ± 1.55 versus 5.29 ± 1.52 ng · h/mL; study 2, 31.51 ± 10.95 versus 31.23 ± 10.33 ng · h/mL; study 3, 50.16 ± 14.91 versus 49.01 ± 14.03 ng · h/mL) and C(max) (0.38 ± 0.11 versus 0.37 ± 0.12 ng/mL; 2.37 ± 1.20 versus 2.41 ± 0.94 ng/mL; 5.87 ± 1.99 versus 5.63 ± 2.26 ng/mL) under all conditions. The 90% confidence intervals for plasma oxymorphone AUC(0-t), AUC(0-inf), and C(max) fulfilled the bioequivalence criterion. Adverse event rates were similar with Oxy-ER and Oxy-CRF (study 1, 25% versus 23%; study 2, 9% versus 16%; study 3, 20% each group). CONCLUSION: Oxy-CRF and Oxy-ER (5 mg and 40 mg) are bioequivalent under fasted and fed conditions, suggesting that Oxy-CRF will have clinical efficacy and safety equivalent to Oxy-ER.

Concurrent induction and mechanism-based inactivation of CYP3A4 by an L-valinamide derivative.

DPC 681 (N-[(3-fluorophenyl)methyl]glycyl-N-[3-[((3-aminophenyl) sulfonyl)-2-(aminophenyl)amino]-(1S,2S)-2-hydroxy-1-(phenyl-methyl)propyl]-3-methyl-l-valinamide) is a potent peptide-like human immunodeficiency virus protease inhibitor that was evaluated in phase I clinical trials. In primary cultures of hepatocytes, DPC 681 significantly induced the testosterone 6beta-hydroxylase activity of rat CYP3A, but not human CYP3A4. Western blot analysis, however, demonstrated a 3-fold increase in expression of CYP3A4 protein by 20 microM DPC 681 in primary cultures of human hepatocytes. Subsequent studies showed that DPC 681 was a potent inhibitor of human CYP3A4 (IC50 = 0.039 microM) and rat CYP3A (IC50 = 1.62 microM). Moreover, DPC 681 was a mechanism-based inactivator of CYP3A4 with KI and kinact of 0.24 microM and 0.22 min-1, respectively. Thus, DPC 681 is both a potent inhibitor and a strong inducer of CYP3A4. Induction of CYP3A4 by DPC 681 was masked in vitro by autoinactivation, similar to the protease inhibitor ritonavir. In pharmacokinetic studies in healthy human volunteers and rats, DPC 681 was found to highly autoinduce its metabolism. Human volunteers dosed with DPC 681 at 600 mg twice daily for 14 days had a 75% decrease in the mean area under the concentration-time curve and a more than 3-fold increase in apparent clearance as compared with that on day 1. Because the primary route of DPC 681 clearance is via CYP3A metabolism, the increased clearance observed in clinical studies is due to induction of human CYP3A4 expression.

Hepatic but not intestinal CYP3A4 displays dose-dependent induction by efavirenz in humans.

OBJECTIVE: The capacity of the non-nucleoside reverse transcriptase inhibitor efavirenz to induce either liver CYP3A4 or intestinal CYP3A4, or both, as well as intestinal P-glycoprotein, was evaluated in healthy volunteers during and after a 10-day treatment course with two different daily doses. METHODS: Cohorts of 12 healthy subjects were randomized (2:1) to receive either efavirenz or placebo orally for 10 days. The first cohort received 200 mg efavirenz and the second cohort received 400 mg efavirenz daily. Liver CYP3A4 activity was evaluated on 9 different occasions with use of the erythromycin breath test (ERMBT). Intestinal biopsy specimens were obtained before the first dose of efavirenz and on the day after administration of the last dose to measure intestinal CYP3A4 and P-glycoprotein contents by immunoblotting. Efavirenz plasma levels were measured by HPLC, and pharmacokinetic parameters were determined by standard noncompartmental methods. RESULTS: Efavirenz significantly increased the mean ERMBT result in a dose- and time-dependent manner, with a 55% mean induction at 400 mg and a 33% mean induction at 200 mg (P <.01, compared with placebo for each treatment). The efavirenz AUC on day 10 correlated with the magnitude of induction (day 11/day 1 ERMBT ratio) when the two dose groups were combined (r = 0.509; P =.04). In contrast, efavirenz treatment had no detectable effect on intestinal CYP3A4 or P-glycoprotein. CONCLUSIONS: Efavirenz is an inducer of liver CYP3A4 in healthy volunteers, and interpatient differences in magnitude of induction is partly explained by variation in systemic drug exposure. However, efavirenz did not appear to induce intestinal CYP3A4 or intestinal P-glycoprotein. These results suggest that drug interactions caused by induction of CYP3A4 can be liver specific.

Lack of Pharmacokinetic Interaction between Aspirin and Warfarin.

An open-label, randomized, two-phase crossover study was conducted on 36 healthy male volunteers to identify the effects of coadministration of aspirin (acetylsalicylic acid; ASA) and crystalline warfarin sodium (Coumadin((R))) on the elimination and disposition kinetics of ASA, salicylic acid (SA) and R- and S-warfarin enantiomers. Twenty-four subjects were administered single doses of 325 mg of ASA alone and in combination with 10 mg of crystalline warfarin sodium with a 1-week washout between ASA doses. ASA and SA pharmacokinetic parameters were determined after each dose. Twelve subjects were administered single doses of 10 mg of crystalline warfarin sodium alone and in combination with 325 mg of ASA with a 4-week washout between warfarin doses. R- and S-warfarin enantiomer pharmacokinetic parameters were determined after each dose. Pharmacokinetic parameters were compared using analysis of variance and 90% confidence intervals. ASA and SA AUCs (the area under the plasma concentration versus time curve from time zero to time infinity) respectively were 3.28 plus minus 0.80 and 66.99 plus minus 11.73 &mgr;g h ml(minus sign1) (ASA alone), and 3.22 plus minus 0.61 and 69.48 plus minus 15.79 &mgr;g h ml(minus sign1) (ASA with warfarin). R-warfarin and S-warfarin AUCs respectively were 33.9 plus minus 9.3 and 23.9 plus minus 16.0 &mgr;g h ml(minus sign1) (warfarin alone) and 33.6 plus minus 10.2 and 22.6 plus minus 14.7 &mgr;g h ml(minus sign1) (warfarin with ASA). The only pharmacokinetic parameter which was statistically significantly different when the combination was administered was the S-warfarin elimination rate constant (p < 0.05), but the difference (9.2% increase in the presence of ASA) was small and no significant difference was found in S-warfarin clearance. It is concluded that there is no pharmacokinetic interaction when a single dose of ASA 325 mg is coadministered with a single dose of crystalline warfarin sodium 10 mg.