Opioid dependence in pregnancy

 

During the pregnancy, the mother can choose to remain on a maintenance regime or begin a controlled withdrawal program using methadone or buprenorphine in order to reduce the risk of Neonatal Abstinence Syndrome (NAS).

 

Buprenorphine is not licensed for use in pregnancy in the UK but should be continued if the patient is already stable on this drug.

 

Withdrawal should not be sudden due to the risk of foetal death and only carried out during the 2nd trimester at a reducing rate of 2-3mg every 3-5 days. Withdrawal in the 1st trimester carries a risk of miscarriage, whereas in the 3rd trimester, the withdrawal effect on the mother can cause foetal distress and still birth. Metabolism is increased in the 3rd trimester, so higher or more frequent doses of methadone may need to be given.

 

The MOTHER study (Maternal Opioid Treatment: Human Experimental Research) was a double dummy, double blind, random controlled trial which compared the use of buprenorphine versus methadone during pregnancy. It found that buprenorphine was preferential due to reduced severity of the NAS, less morphine being required for treatment (1.1mg versus 10.4mg with methadone) and the time spent in hospital was reduced after birth. During gestation it was also found that there was improved foetal heart rate and more frequency of movement.