PII-024 - CHARACTERIZING METHADONE:METABOLITE RATIO DURING METHADONE INDUCTION IN PREGNANCY

R. Boelig¹, D. Hand², G. Kaushal², S. Jain², W. Kraft¹; ¹Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA, ²Thomas Jefferson University, Philadelphia, PA, USA.

Background: Opioid use disorder (OUD) remains a pressing problem in the country, with an increasing impact on pregnant patients. Methadone is commonly used for management of OUD in pregnancy, however there are no standardized dosing protocols, and earlier work has demonstrated altered methadone metabolism in pregnancy.

Methods: We conducted a prospective study of 40 pregnant patients admitted for methadone induction in pregnancy. Participants were enrolled at a time at which they felt well enough to offer informed consent. Methadone induction protocol involved an initial dose of 30mg with an additional 10mg every 4 hours as needed based on withdrawal symptoms; these doses were added to inform the next daily morning doses. Methadone and EDDP concentration in plasma was assessed prior to daily morning methadone dose and 4 hours after to calculate a methadone metabolite ratio(MMR). Clinical Opioid Withdrawal Scale (COWS) was also assessed pre-dose and 4 hours post dose.

Results: 40 participants were enrolled. 8 (20%) in 1st trimester, 21 (52.5%) in the 2nd trimester, and 11 (27.5%) in the 3rd trimester. There was a significant increase in MMR pre vs post dose (4.8+/-2.3 vs 9.8+/-4.0, MD5.0(4.3-5.6), p< 0.001). There was also a strong relationship between daily dose and MMR measured 4 hours post dose (Figure, p=0.016 in regression analysis). Although there appeared to be a lower MMR in the 3rd trimester, this was not statistically significant in regression analysis (p=0.57)

Conclusion: Methadone:metabolite ratio in pregnancy varies by dose during the induction period in pregnancy. Further research is needed on how MMR can inform dose titration during initial induction in pregnancy