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Poster presented at: CPDD Scientific Meeting, San Juan, PR.

Aims: NAS incidence & severity in infants exposed to methadone during gestation is independent of maternal methadone dose. The incidence & severity of NAS could be in part due to genetic variability of key genetic loci related to opioid response; the interleukin-1beta (IL-1B) & mu opioid receptor (OPRM1) genes. This study aimed to investigate the impact of genetic variability in IL-1B -31 or OPRM1 A118G on NAS incidence (treatment required) & severity (dose of morphine).

Methods: This pilot study collected cheek cells from 71 methadone exposed infants; 46 required treatment. Complete genetic & morphine treatment data were obtained for a subset of 26 NAS infants.

Results: There were no difference in IL-1B or OPRM1 genotypes between infants with, & without NAS (OR (p) = 1.9 (0.21) and 0.23 (0.24), respectively). There was also no impact of genetic variability at IL-1B and OPRM1 on morphine treatment (median, mg): initial morphine dose – wild-type (WT, n = 21) 0.15 and variant (Var, n = 5) 0.2 (p = 0.06) and WT (n = 24) 0.17 and Var (n = 2) 0.22 (p = 0.73), respectively; maximum morphine dose – WT (n = 21) 0.3 and Var (n = 5) 0.28 (p = 0.94) and WT (n = 24) 0.29 and Var (n = 2) 0.24 (p = 0.39), respectively; and total morphine in the first month of life – WT (n = 20) 33.8 and Var (n = 5) 34.8 (p = 0.67) and WT (n = 23) 34.8 and Var (n = 2) 25.4 (p = 0.38), respectively.

Conclusions: Despite genetic variability at these loci being reported to impact opioid response in adults, our study to date has not replicated these findings in infants. However, infant numbers in each genotype group were low. Therefore, the possibility remains for an association between genetic variability and NAS, leading to predictive tools to pre-determine NAS incidence & severity. Data collection for this project continues.

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Neonatal abstinence syndrome in methadone exposed infants: Role of genetic variability, poster


Pharmacy and Pharmaceutical Sciences

Neonatal abstinence syndrome in methadone exposed infants: Role of genetic variability