Chronic intrathecal application of morphine: Distribution of morphine and its metabolites in spinal fluid and serum

In our department from 1988- 1996 165 pump implantations for chronic intractable pain syndromes were performed. Here we report on the concentrations of morphine and its glucuronides in serum and spinal fluids of patients who recieved intrathecal morphine therapy. Intrathecal levels of morphine (11-176 mg/l) were very high when compared to the serum morphine levels (0-0.035 mg/l). Glucuronide concentrations were much higher in serum (10-423 mu g/l) than in liquor (0-84 mu g/l). On that account we assume that in intrathecal application the main analgetic effect still can be contributed to morphine. The clinical effect seems to be influenced by the position of the catheter tip because local diffusion difficulties cause an uneven distribution of intrathecal morphine.