What are the opioid considerations for patients with hepatic and renal dysfunction?
With hepatic and renal dysfunction being common comorbidities in the elderly, it is essential to take into the account the severity of dysfunction when prescribing opioids. Hydromorphone, oxycodone, and methadone metabolism is dependent on the function of the liver and should therefore be avoided in patients with significant liver impairment. Fentanyl is therefore the opioid of choice with liver dysfunction.
Morphine undergoes hepatic metabolism and is broken down into two metabolites: morphine-6-glucoronide (M6G) and morphine-3-glucoronide (M3G). These metabolites undergo enterohepatic circulation and are then excreted through the bile/feces and the urine. M3G has neuroexcitatory effects and therefore has detrimental effects secondary to accumulation in patients with renal impairment with potential for inducing convulsions. M6G, on the other hand, is a potent opioid analgesic.