MORPHINE AND MORPHINE-GLUCURONIDE CONCENTRATIONS IN PLASMA AND CSF DURING LONG-TERM ADMINISTRATION OF ORAL MORPHINE

Concentrations of morphine, morphine-3-glucuronide (M3G) and morphine- 6-glucuronide (M6G) were measured by h.p.l.c. in plasma and cerebrospi nal fluid (CSF) samples from 16 patients with cancer receiving oral (c ontrolled-release) morphine. There was a close correlation between pla sma and CSF morphine concentrations (r = 0.94, P = 0.0001) and both co rrelated with drug dosage (r = 0.61, P = 0.013 and r = 0.74, P = 0.000 1, respectively). M3G and M6G in plasma and CSF were correlated (r = 0 .81 and r = 0.82, both P = 0.0001). No relationship was apparent betwe en M plus M6G concentrations in the CSF and pain scores.