Q: What is "rebound pain" effect of morphine in Hemodialysis patients? 

 Answer: Morphine and its metabolites get removed with dialysis and may cause “rebound” pain effect. 

Patient with renal insufficiency but not on dialysis should receive morphine with caution. Morphine gets metabolized in the liver to morphine-3-glucuronide, morphine-6-glucuronide and normorphine, which are excreted via kidneys. About 10% of Morphine remain unchanged. Though parent compound gets excreted fine in renal insufficiency, excretion of metabolites get compromised in renal insufficiency.

The worrisome metabolite of morphine is morphine-6-glucuronide, also known as M6G. It is extremely potent (more than its parent compound), crosses the blood-brain barrier and may cause life-threatening respiratory depression as well as hallucinations. Though it is removable via dialysis (which takes away analgesic effect and causes rebound pain effect), it takes a long time to diffuse out of CNS and continue to have CNS depression effect. Moreover, on the other hand, morphine-3-glucuronide (M3G) causes behavioral excitation. 

In conclusion, Morphine in patients with renal insufficiency can cause very unpredictable effects.


Reference: 

 Dean M. Opioids in renal failure and dialysis patients. J Pain Symptom Manage. 2004;28:497-504.