Opiates have altered pharmacokinetics in renal failure.

• Morphine is renally excreted. It has a half-life of 50 hours in patients with end stage renal failure, compared to 3-5 hours in patients with normal renal function.
• Therefore, patients with renal dysfunction are at much higher risk of opiate toxicity.

You should always consider using non-opioid drugs in these patients whenever possible. If they are necessary, those that tend not to accumulate in renal disease, such as buprenorphine or alfentanil, may be preferred for mild and more severe pain, respectively.

• Note that the elimination of tramadol is primarily by the hepatic route (metabolism by CYP2D6 to an active metabolite and by CYP3A4 and CYP2B6) and partly by the renal route (up to 30% of dose) therefore can be safer to use than morphine in this patient cohort.