Morphine sulphate for the treatment of neonatal abstinence syndrome in methadone and buprenorphine exposed infants

Abstract

Aim: Determine morphine’s effectiveness in ameliorating Neonatal Abstinence Syndrome (NAS) in methadone and buprenorphine exposed infants. Method: Prospective, non-randomised comparison study with fl exible maternal dosing. Maternal doses were stable prior to delivery for (median, range) 5.5, 1–31 weeks for methadone (dose at delivery 35.0, 17.5–140.0 mg/day) and 10, 1–37 weeks for buprenorphine (6, 2–20 mg/day). Participants were buprenorphine, methadone and non-opioid exposed control infants (25 infants per group). NAS was assessed over a 4-week postnatal period, 4-hourly until hospital discharge, then weekly scoring, using a Modifi ed Finnegan Withdrawal Scale (MFWS), max score 41. Oral morphine sulphate (1 mg/ml) was commenced 4-hourly when scores of ≥8 were achieved on 3 consecutive scoring sessions or when there was an average of 3 scores ≥8. For MFWS scores of 8–10: 0.5 mg/kg/day, 11–13: 0.7 mg/kg/day, 14+: 0.9 mg/kg/day of morphine was administered. Results: There was no significant difference between methadone and buprenorphine groups in the percentage of infants requiring treatment (60% and 48% respectively). No control infants scored above 7 on the MFWS. For treated infants, more (p < 0.05) morphine was administered to methadone (37.07, 17.08–66.79 mg) compared to buprenorphine (27.38, 0.5–45.68 mg) exposed infants to attempt to control NAS. For treated infants, there was no signifi cant difference in birth weight or length of hospital stay between methadone and buprenorphine groups. Following treatment initiation, more (p < 0.01) methadone (87%) compared to buprenorphine (42%) exposed infants continued to exceed the threshold score for morphine treatment requirement. However, there was no significant difference in the number of times this occurred between groups (methadone: 7, 1–29; buprenorphine: 5, 1–68). Conclusion: Methadone compared to buprenorphine exposed infants, required signifi cantly more morphine to control NAS, indicating greater NAS severity. The morphine regimen used was not entirely effective in ameliorating NAS to non-opioid exposed control levels in methadone or buprenorphine groups, furthermore, the regimen may be less effective in methadone compared to buprenorphine exposed infants.