Association of methadone dose with substance use and treatment retention in pregnant and postpartum women with opioid use disorder.

BACKGROUND

In non-pregnant individuals being treated for opioid use disorder (OUD) with methadone, doses ≥60mg per day are associated with improved treatment retention and decreased illicit opioid use. Although methadone remains the first line treatment for OUD in pregnant women, there are no studies replicating this finding in pregnancy.

METHODS

We conducted a retrospective cohort study of 189 pregnant women treated with methadone for OUD from 2006 to 2013. Chart data collected included demographics, pregnancy dates, methadone doses, and urine drug screen (UDS) results.

RESULTS

Treatment retention at delivery was significantly higher for subjects taking ≥60mg of methadone (90.1% v. 74.1% p<0.005), as was treatment retention at 60days postpartum (71.6% v. 37.0%, p<0.0001). Percent of UDS results negative for illicit substances during pregnancy was also significantly higher for subjects taking ≥60mg (71.5% v. 58.0%, p<0.04). There was no significant difference in UDS results in the first 60days postpartum (63.9% v. 68.1%). Generalized linear models showed a significant positive relationship between methadone dose and treatment retention at delivery (p<0.02) and at 60days postpartum (p<0.004) as well as a significant positive relationship between length of time in treatment and treatment retention at delivery (p<0.04) and at 60days postpartum (p<0.007). Maternal age and percent of negative UDS results were not predictive of treatment retention in either model and there was no significant interaction effect between methadone dose and percent negative UDS results.

CONCLUSIONS

In this cohort, women taking ≥60mg of methadone during pregnancy were more likely to remain in treatment and to provide urine samples negative for illicit drugs. Multivariate modeling suggested a dose dependent response across the entire dose range, rather than a threshold effect at 60mg.