What is the role of methadone in the pathogenesis of neonatal abstinence syndrome (NAS)?

Updated: Dec 20, 2017
  • Author: Ashraf H Hamdan, MD, MBBCh, MSc, MRCP, FAAP; Chief Editor: Santina A Zanelli, MD  more...
  • Print

Methadone maintenance has been an acceptable form of therapy for opiate-dependent pregnant women since the late 1960s. This is currently the recommended treatment for opioid-dependent pregnant women; when properly used, methadone is considered relatively safe for the fetus. Methadone has been shown to decrease illicit behaviors, improve prenatal care and obstetric outcomes, and prevent acute maternal withdrawal that is associated with fetal death. [9] However, maternal methadone use is also associated with NAS, and its effects on the fetus are similar to the effects of heroin. Methadone's half-life is longer than 24 hours, and acute withdrawal may occur within the first 48 hours after birth and as long as 7-14 days later. The withdrawal may even be delayed for as long as 4 weeks after birth, with subacute signs developing as late as 6 months after birth. Neonates face an increased risk of fetal distress and demise, impaired fetal growth, and an increased risk of sudden infant death syndrome (SIDS). Thrombocytosis may occur in the second week of life and may continue until age 4 months.

The relationship between maternal methadone dosage and NAS is controversial, and the available data are conflicting. Several studies have showed that higher maternal doses are associated with an increase in the risk of preterm birth, the risk of symmetrically smaller infants, and longer hospital stays; the need for treatment for NAS indicates more significant withdrawal symptoms. [9, 10, 11] However, a more recent study showed that the incidence and duration of the NAS is not associated with maternal methadone dose. [12]

Did this answer your question?
Additional feedback? (Optional)
Thank you for your feedback!