Combined analysis of circulating β-endorphin with gene polymorphisms in OPRM1, CACNAD2 and ABCB1 reveals correlation with pain, opioid sensitivity and opioid-related side effects

Background Opioidsare associated with wide inter-individual variability in the analgesic response and a narrow therapeutic index. This may be partly explained by the presence of single nucleotide polymorphisms (SNPs) in genes encoding molecular entitiesinvolved in opioidmetabolism and receptor activation. This paper describes the investigation of SNPs in three genes that have a functional impact on the opioidresponse: OPRM1, which codes for the μ-opioid receptor; ABCB1 for the ATP-binding cassette B1 transporter enzyme; and the calcium channel complex subunit CACNA2D2. The genotyping was combined with an analysis of plasma levels of the opioid peptideβ- endorphinin 80 well-defined patients with chronic low back pain scheduled for spinal fusionsurgery, and with differential sensitivity to the opioidanalgesic remifentanil. This patient group was compared with 56 healthy controls.