Frequent episodes of severe pain occur in patients with sickle cell disease (SCD) and require treatment with potent opioid medications. A new study published in The Journal of Pain reports that SCD patients clear morphine from their blood stream quickly and, therefore, require high doses to achieve optimal analgesia.
Researchers from departments of pediatrics at five U.S. medical centers collaborated on a study of 21 SCD patients to determine the impact of the disease on pharmacokinetics of morphine. Previous studies have shown that accelerated clearance of morphine in children with SCD was associated with increased hepatic and renal blood flow caused by higher cardiac output from chronic anemia in SCD patients. The studies, however, were conducted on children during painful episodes in which drug clearance could have been influenced by hemodynamic and inflammatory changes associated with vaso-occlusion and pain.
For this study, patients selected were young adults with SCD who were not taking opioids or experiencing acute complications of the disorder. All participants received a single 30-minute infusion of morphine sulfate and blood draws were taken at several intervals for a period of 24 hours.
Results showed that the half-life of morphine in the SCD patients was 3 to 10-fold shorter compared to morphine clearance in non-SCD patients. The authors concluded that increased hepatic and renal blood flow and elevated glomular filtration rate are the likely reasons for accelerated clearance of morphine.
The findings have significant clinical implications for determining appropriate morphine doses for SCD patients. To achieve optimal analgesia, higher and more frequent dosing may be required, according to the authors.
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