A single-dose, analytically blinded, randomized, crossover study was conducted in 22 healthy male volunteers to compare the bioavailability of one 20 mg with two 10 mg controlled-release (CR) oxycodone tablets. In addition, pharmacodynamic effects were assessed using both objective and subjective measures for up to 48 hr after dosing. The two treatments were bioequivalent, with comparable rates (Cmax of one 20 mg tablet was 109% of two 10 mg tablets; 90% confidence limits: 98.4%-120%) and extents (AUC0-infinity: 107%; 100%-114%) of absorption. In addition, no significant differences between tablets were found for mean values of Tmax, T/12abs, or T/12elim. Correlations between plasma oxycodone concentrations and most pharmacodynamic measures were significant. The strongest correlations were observed for pupil size (r = -0.53) and subjects' assessment of drug effect (r = 0.53), with changes in plasma concentration accounting for more than 25% of the observed changes in these variables. This study demonstrated bioequivalence of two 10 mg and one 20 mg CR oxycodone tablet, with significant correlation between plasma oxycodone concentrations and pharmacodynamic effects in normal volunteers.

The bioavailability and clinical effects of an oral controlled-release morphine sulfate tablet, MS-contin (MSC; Purdue-Frederick, Norwalk, CT) in comparison to an immediate-release (IRMS) preparation were evaluated in normal subjects and cancer patients, respectively. The inherent slow-release character of MSC was confirmed by 2 1/2 X T1/2 absorption rate, one-half Cmax, and twice Tmax relative to IRMS. The T1/2 elimination of the two morphine preparations was similar, demonstrating insignificant risk of MSC accumulation. The difference in the mean number of side effects experienced by the control group per subject was significant (.70 for MSC and 1.26 for IRMS, P = .05) and was consistent with peak plasma morphine attenuation. The cancer patients were initially switched from their previous analgesic to four hourly IRMS and then to MSC at double the dose every eight hours. The majority had their MSC dosing interval lengthened to every 12 hours with a decrease in the total daily morphine requirement. While the mean duration on MSC was 20.5 days, many patients were followed poststudy for an extended period with no appreciable development of tolerance. Overall, MSC analgesia and side effects were perceived by the patients as superior compared with prestudy opioids. The advantage of less frequent dosing may lead to improvement of the quality of life of cancer patients.

The pharmacokinetics of oral morphine sulphate as controlled release tablets ('MS-Contin') and solution were compared at steady-state. Plasma morphine concentrations were determined over 24 hours following the last dose of each drug when given in a randomised, crossover fashion to healthy subjects. Radioimmunoassay was used, which was sensitive yet provided good specificity relative to high-performance liquid chromatography. Controlled release tablets had 86% the bioavailability of the solution. Although each dose of controlled release tablets was double that of the solution, their peak plasma concentrations were the same. Time to maximum concentration was 3 times longer for controlled release tablets with an absorption half-life twice that of the solution. Elimination of both drugs was similar and biphasic with the minor terminal portion at 10 times the half-life of the major early process. These data explain the analgesic duration of 12 hours observed in clinical studies and the lack of accumulation with morphine compared with methadone.

No abstract

The results of nine US multicenter, sequential crossover, dose titration studies of controlled-release oral morphine (MS Contin 30 mg tablets [MSC], Purdue Frederick, Norwalk, CT) are reviewed in Part I. The studies demonstrated the prolonged analgesic efficacy of the preparation in the treatment of patients with moderate to severe cancer-related pain. Approximately 93% of the patients achieved satisfactory to excellent analgesia on a 12-hour regimen when appropriate dose titration was allowed. The remaining patients were successfully maintained on an 8-hour regimen. The preparation was well-tolerated and comparable in safety to immediate-release oral morphine. In global evaluations, MSC was judged to be significantly (P less than 0.05) more effective, and with significantly (P less than 0.05) fewer side effects than both the prestudy opioid analgesics and 4-hour immediate-release oral morphine. Patients had a broad range of morphine requirements (mean daily MSC dose, 240 mg; range, 60 mg/day to 1800 mg/day); therefore various MSC tablet strengths were developed. Part II presents three studies in which the MSC formulations (15-mg, 60-mg, and 100-mg tablets) were compared to the 30-mg tablet within three randomized, single-dose, two-way crossover, analytically blinded bioavailability protocols, to determine bioequivalence and dose proportionality. The maximum morphine concentration, time of maximum morphine concentration, and area under the plasma morphine versus 12-hour and 24-hour time curve (AUC 0.12; AUC 0.24) were determined in each study. There were no significant differences between the values associated with MSC 1 X 30 mg tablet and 2 X 15 mg tablets (study 1), MSC 2 X 30 mg tablets and 1 X 60 mg tablet (study 2), and MSC 3 X 30 mg tablets and 1 X 100 mg tablet (study 3, values adjusted to dose of 90 mg), except for one marginally significant difference in study 3 (AUC 0.24; P = 0.04) which was not clinically or biopharmaceutically significant. The results showed that MSC 15-mg, 30-mg, 60-mg, and 100-mg dosage strengths are bioequivalent and dose proportional, and, therefore, therapeutically interchangeable. It was concluded that with routine assessment of the patient and adherence to the principles of analgesic dosing, MSC can be successfully used to control cancer-related pain. Furthermore, the availability of various MSC tablet strengths can be expected to facilitate the analgesic management of a patient population with widely differing opioid requirements.