Wild-type OPRM1-AA genotype carriers reported a significantly higher number of adverse events than OPRM1-AG/GG (median [p25-75], 7 [5-11] vs 5 [3-9]), particularly gastrointestinal system events (90% vs 63%) such as nausea (33% vs 0%).
Synthetic and Receptor Signaling Explorations of the Mitragyna Alkaloids: Mitragynine as an Atypical Molecular Framework for Opioid Receptor Modulators.
Genetic variation at position 118 of the mu-opioid receptor is associated with interindividual differences in pain scores, self-administered intravenous morphine, and the incidence of nausea postoperatively.
In carriers of the mutated G118 allele of the mu-opioid receptor, the potency of the pupil-constricting effects of morphine-6-glucuronide and morphine was significantly smaller, and carriers of the G118 allele reported less nausea and vomited less often after administration of morphine-6-glucuronide.