Pharmacogenetics of opioids for the treatment of acute maternal pain during pregnancy and lactation.

There have been an increasing number of clinical studies investigating the relationship between interindividual genetic variability and the safety and efficacy of opioid analgesics. Despite the widespread use of opioids in pregnant and lactating women for the treatment of acute pain, few studies have investigated the interplay of genetic factors and pregnancy-related physiological alterations in relation to opioid metabolism and response. Some interesting avenues of research require further pursuit- including evidence of cytochrome P450 2D6 (CYP2D6) induction during pregnancy and its effect on the generation of the active opioid metabolites morphine, oxymorphone, O-desmethyltramadol, and hydromorphone following the administration of codeine, oxycodone, tramadol, and hydrocodone respectively. Studies investigating the duration of maternal CYP2D6 induction after delivery are also needed to shed light on genotype to phenotype correlations in breastfeeding mothers using opioid analgesics in the postpartum period.