• For example, morphine clearance decreases only modestly in patients with renal impairment, but clearance of its M6G and M3G metabolites decreases dramatically.105-107 Accumulation of morphine glucuronides in patients with renal impairment has been associated with serious adverse effects, including respiratory depression, sedation, nausea, and vomiting.73,74,108 Similarly, patients with chronic ren