Urine and plasma pharmacokinetics of lofexidine after oral delivery in opiate-dependent patients.

OBJECTIVES: The objective of this study was to investigate lofexidine urine and plasma pharmacokinetics using three different dosing regimens in opioid dependent subjects. To date, there have been no published studies on lofexidine appearance and excretion in urine of opioid dependent subjects. METHODS: Subjects were stabilized with 100 mg morphine sulphate on days 3-8 of the study. The dosing regimens of lofexidine hydrochloride were .8 mg twice a day (BID), 1.2 mg BID, or .8 mg three times a day (TID) on days 9 through 16 of the study. Plasma and urine samples were collected at appropriate time points. Area under the concentration-time curve (AUC), maximum concentration in plasma (C(max)), time when maximum concentration was reached (T(max)) and fraction excreted unchanged in urine (Fe) were calculated. RESULTS: The average half-life obtained from all profiles was 12.1 +/- 6.3 hr. Steady-state (SS) was reached by study day 15. The plasma pharmacokinetic parameters for 1.2 mg BID and .8 mg TID dosing regimens did not seem to be different at steady state (day 15). T(max) was not statistically significantly different across dosing regimens. Fe values ranged between .01% and 34% with high variability within the same dosing regimen. For the total dose of 2.4 mg/day the two dosing regimens that were evaluated, namely 1.2 mg BID and .8 mg TID, did not show a significant statistical difference in plasma and urine pharmacokinetic parameters. CONCLUSION: Although preliminary due to the limited number of subjects, these findings are the first to document lofexidine urine pharmacokinetics in opiate addicts using a highly sensitive liquid chromatography tandem mass spectrometric analysis.

A Phase 3 placebo-controlled, double-blind, multi-site trial of the alpha-2-adrenergic agonist, lofexidine, for opioid withdrawal.

CONTEXT: Lofexidine is an alpha-2-adrenergic receptor agonist that is approved in the United Kingdom for the treatment of opioid withdrawal symptoms. Lofexidine has been reported to have more significant effects on decreasing opioid withdrawal symptoms with less hypotension than clonidine. OBJECTIVE: To demonstrate that lofexidine is well tolerated and effective in the alleviation of observationally defined opioid withdrawal symptoms in opioid dependent individuals undergoing medically supervised opioid detoxification as compared to placebo. DESIGN: An inpatient, Phase 3, placebo-controlled, double-blind, randomized multi-site trial with three phases: (1) opioid agonist stabilization phase (days 1-3), (2) detoxification/medication or placebo phase (days 4-8), and (3) post detoxification/medication phase (days 9-11). SUBJECTS: Sixty-eight opioid dependent subjects were enrolled at three sites with 35 randomized to lofexidine and 33 to placebo. MAIN OUTCOME MEASURE: Modified Himmelsbach Opiate Withdrawal Scale (MHOWS) on study day 5 (second opioid detoxification treatment day). RESULTS: Due to significant findings, the study was terminated early. On the study day 5 MHOWS, subjects treated with lofexidine had significantly lower scores (equating to fewer/less severe withdrawal symptoms) than placebo subjects (least squares means 19.5+/-2.1 versus 30.9+/-2.7; p=0.0019). Lofexidine subjects had significantly better retention in treatment than placebo subjects (38.2% versus 15.2%; Log rank test p=0.01). CONCLUSIONS: Lofexidine is well tolerated and more efficacious than placebo for reducing opioid withdrawal symptoms in inpatients undergoing medically supervised opioid detoxification.

Clinical pharmacokinetics of lofexidine, the alpha 2-adrenergic receptor agonist, in opiate addicts plasma using a highly sensitive liquid chromatography tandem mass spectrometric analysis.

OBJECTIVES: The objective of this investigation was to characterize the pharmacokinetic profile of lofexidine. Lofexidine is an orally bioavailable alpha 2-adrenergic receptor agonist analogue of clonidine that acts centrally to suppress opiate withdrawal symptoms. METHODS: During the detoxification period of a phase 3 placebo-controlled, randomized, double-blind trial, six subjects were entered in this preliminary pharmacokinetic study. RESULTS: Pharmacokinetic analysis of plasma samples collected during study day 7 indicated that C(max) was 3242 +/- 917 ng/L. The mean trough levels between the study days were not significantly different (p > .05), suggesting that the subjects were at steady-state. CONCLUSIONS: Although preliminary due to the limited number of subjects, these findings are the first to document lofexidine clinical pharmacokinetics in opiate addicts using a highly sensitive liquid chromatography tandem mass spectrometric analysis.

A randomized, double-blind, placebo-controlled safety study of high-dose dextromethorphan in methadone-maintained male inpatients.

The NMDA antagonist dextromethorphan hydrobromide (DM) may be useful in the treatment of opioid dependence, particularly as a means of reducing tolerance to methadone during replacement therapy. As a prelude to clinical efficacy studies, a randomized, double-blind, placebo-controlled study examined the safety of DM in combination with methadone in inpatient, opiate-dependent volunteers. Male participants received daily methadone (50-70 mg/day) and either DM (n=10) or placebo (n=5) during the 12-day active medication phase of the study. DM participants received doses of 120, 240, and 480 mg/day in increasing order (4 days each). DM at high doses caused mild elevations of heart rate, blood pressure, temperature, and plasma bromide. However, none of these effects was clinically significant. DM caused no significant changes in respiration, pupil diameter, or subjective drug effects measured by standard scales. Participants in the DM group reported many more adverse events than did subjects on placebo (173 vs. 21), but these effects were not clinically serious. The most commonly reported side effects were sleepiness and drowsiness. Several participants reported intoxicating effects at the highest dose. Overall, DM was well-tolerated by the methadone-maintained opiate-dependent subjects studied here. These results support the further exploration of DM as an adjunct medication during methadone replacement therapy.