The study, which was published online today in Anesthesiology, was prompted by past genetic studies in animals that have shown a strong genetic component in the response to opiates. My colleague Tracie White describes the work and the Stanford team's findings in a release:
Researchers recruited 121 twin pairs for the randomized, double-blinded and placebo-controlled study. Pain sensitivity and analgesic response were measured by applying a heat probe and by immersing a hand in ice-cold water, both before and during an infusion of the opiate alfentanil, a short-acting painkiller prescribed by anesthesiologists. The team also compared individual variations in levels of sedation, mental acuity, respiratory depression, nausea, itch, and drug-liking/disliking -- a surrogate measure of addiction potential -- between identical twins, non-identical twins and non-related subjects. This provided an estimate of the extent to which variations in responses to opiates are inherited. For example, the finding that identical twins are more similar in their responses to opiates than non-identical twins suggested inheritance plays a significant role.
Heritability was found to account for 30 percent of the variability for respiratory depression, 59 percent of the variability for nausea and 36 percent for drug disliking. Additionally, up to 38 percent for itchiness, 32 percent for dizziness and 26 percent for drug-liking could be due to heritable factors. An earlier study published by the same researchers [in March online in] Pain reported that genetics accounted for 60 percent of the variability in the effectiveness of opiates in relieving pain.
Martin Angst, MD, professor of anesthesia and one of two principal investigators for the study, commented on the significance of the findings saying:
The study is a significant step forward in efforts to understand the basis of individual variability in response to opioids and to eventually personalize opioid treatment plans for patients... Our findings strongly encourage the use of downstream molecular genetics to identify patients who are more likely or less likely to benefit from these drugs--to help make decisions on how aggressive you want to be with treatment, how carefully you monitor patients and whether certain patients are suitable candidates for prolonged treatment.
Previously: Report shows over 60 percent of Americans don't follow doctors' orders in taking prescription meds and Study shows prescribing higher doses of pain meds may increase risk of overdose
Photo by Lia Steakley