PLASMA-CONCENTRATIONS AND RENAL CLEARANCE OF MORPHINE, MORPHINE-3-GLUCURONIDE AND MORPHINE-6-GLUCURONIDE IN CANCER-PATIENTS RECEIVING MORPHINE

The plasma concentrations and renal clearance values of morphine, morp hine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) were determi ned in 11 adult cancer patients maintained on a long term oral morphin e dosage (10 to 100mg every 4h). Concentrations in plasma and urine we re determined by a specific high performance liquid chromatography ass ay. In this group of patients, whose creatinine clearance values range d from 52 to 180 ml/min (3.12 to 10.8 L/h), average steady-state plasm a concentrations of morphine, M3G and M6G were related (p < 0.01) to t he morphine dose per kilogram of bodyweight. The mean total urinary re covery as morphine, M3G and M6G was 74.6 +/- 26.5% of the dose. Renal clearance values for M3G and M6G were closely related (r2 = 0.80; p < 0.0005). It was not possible to detect a relationship between the rena l clearance of morphine, M3G and M6G, and that of creatinine. The rena l tubular handling of all 3 compounds showed wide interindividual vari ation, and there was evidence of either net renal tubular secretion or reabsorption. There was no apparent relationship between plasma morph ine and M6G concentrations and pain relief.