Nausea and vomiting are probably the most unpleasant side effects that occur when morphine used. A number of studies have investigated the effect on pain relief of single nucleotide polymorphisms (SNPs) in genes involved in morphine's metabolism, distribution, binding, and cellular action. The mechanism through which morphine causes nausea and vomiting has not been elucidated clearly. We examined all the reported SNPs which are associated with the complications of morphine, including SNPs in genes for phase I and phase II metabolic enzymes, ABC binding cassette drug transporters, κ and δ opioid receptors, and ion channels implicated in the postreceptor action of morphine.
A prospective, observational study in 129 female patients was conducted to investigate the effect of 14 SNPs on nausea or vomiting induced by intravenous patient-controlled analgesia (IVPCA) with morphine after gynecology surgery. Clinical phenotype, subjective complaints, and objective observations were recorded. DNA from blood samples was used to record the SNPs. Eleven SNPs were then analyzed further.
No significant association with the presence of phenotype (nausea or vomiting) versus genotype was observed (all P > .05). No significant association with severity of phenotype versus genotype of the 11 SNPs was observed except for unadjusted data for rs2737703.
There was no significant difference between severity or incidence of IVPCA morphine-induced nausea and vomiting and genotype (11 SNPs). Further study should perhaps be focused on mRNA and proteinomics rather than SNPs.