Novel Associations between FAAH Genetic Variants and Postoperative Central Opioid related Adverse Effects

Opioid effects are potentiated by cannabinoid agonists including anandamide, an endocannabinoid. Inter-individual variability in responses to opioids is a major clinical problem. Multiple deaths and anoxic brain injuries occur every year in due to opioid induced respiratory depression in surgical patients and drug abusers of opioids and cannabinoids. This study aimed to determine specific associations between genetic variants of fatty acid amide hydrolase (FAAH) and postoperative central opioid adverse effects in children undergoing tonsillectomy. This is a prospective genotype blinded observational study 259 healthy children between 6 and 15 years that received standard perioperative care with a standard anesthetic and an intraoperative dose of morphine were enrolled. Associations between frequent polymorphisms of FAAH and central postoperative opioid adverse effects including, respiratory depression (RD), postoperative nausea and vomiting (PONV) and prolonged stay in Post Anesthesia Recovery Room (PACU) due to RD and PONV were analyzed. Five specific FAAH SNPs had significant associations with more than 2 fold increased risk for refractory PONV (adjusted p<0.0018), and nominal associations (p<0.05) with RD and prolonged PACU stay in white children undergoing tonsillectomy. FAAH SNP, rs324420 is a missense mutation with altered FAAH function and it is linked with other FAAH SNPs associated with PONV and RD in our cohort; association between PONV and rs324420 was confirmed in our extended cohort with additional 66 white children. Specific FAAH polymorphisms are associated with refractory PONV, opioid-related respiratory depression, and prolonged PACU stay due to opioid adverse effects in white children undergoing tonsillectomy.