Plasma and Cerebrospinal Fluid Concentrations of Morphine and Morphine Glucuronides after Oral Morphine

Abstract

We conclude that M-3G and M-6G readily cross the blood-brain barrier in patients with normal renal function or with renal failure. In patients with renal failure, the retention of plasma M-6G induces a progressive accumulation of this active metabolite in CSF; this accumulation may explain the increased susceptibility to morphine in patients with renal failure.