Effect of Functional Polymorphisms in ABCB1 gene on Opioid Doses in Patients with Chronic Low Back Pain

Purpose Opioids are commonly used to treat pain. P-glycoprotein (P-GP) is encoded by the ABCB1 gene and acts as an efflux pump at the blood-brain barrier and reduces the intracellular penetration of opioids. Research suggests single nucleotide polymorphisms (SNP) C3435T and G2677T/A in the ABCB1 gene are associated with higher levels of P-GP expression. We hypothesize that the presence of a CC-GG diplotype will affect opioid doses in patients with chronic low back pain. Methods A total of 71 patients from the PRECISION Pain Research Registry participated in this study. All patients met the NIH criteria for chronic back pain and reported a current use of opioids. Patients were genotyped for the C3435T and G2677T/A SNPs with the Illumina Infinium Global Screening Array. Patient reported drug data was calculated into morphine milligram equivalents (MMEs). Results The mean MMEs for patients with the CC and CT/TT genotypes were 30.4 and 31.0, respectively (p=0.73). The mean MMEs for patients with the GG and GT/TT genotypes were 28.58 and 34.37, respectively (p=0.43). Mean MMEs for a CC-GG diplotype vs other diplotypes were 29.6 and 32.9, respectively (p=0.67). Adjustment for baseline age, gender, pain intensity, pain catastrophizing and pain self-efficacy did not materially affect the observed results. Conclusions We were unable to detect a significant association between these ABCB1 variants and MME doses. This may be potentially attributed to the limited statistical power of this study.