1) General information about opioids
Opioid drugs are a family of drugs that include morphine, heroin, fentanyl and codeine. They are used for pain control and are only available by prescription. They can cause sleepiness and in extreme cases, people stop breathing. When given to breastfeeding mothers, they can pass into milk and affect babies in the same way.
The risk of sleepiness is compounded when opioids are combined with other medications that also have a sedating quality. Side-effects in the baby are also more likely if the baby is premature or at risk of any of the following:
- Not breathing
- Low blood pressure
- Muscle weakness
The babies of mothers using opioids should be closely monitored. It is best to use the lowest possible doses for the shortest time (Ito 2016). Some members of the opioid family are preferred over others.
Codeine is an opioid taken as a pill. Since 2006, it is no longer recommended for use by breastfeeding mothers because it is thought to be dangerous for some babies (Martin 2018).
Some people have a gene (a CYP2D6 super-metabolizer) that results in codeine rapidly being changed into morphine. The gene can occur in anyone but is present in as many as 28% of people with North African, Ethiopian, and Arab origins (Dean 2012). Genetic testing can be done but it is not yet a routine test.
Breastfeeding mothers who have this gene and use codeine may produce breast milk with high levels of morphine. As a result, it is feared their babies may become very sleepy, be unable to breathe, and even die (Madadi 2007).
However, this recommendation may change as it was based on a single highly-publicized case (Zipursky 2020).
Similar concerns have been raised about the use of tramadol, another opioid medication, when more than one dose is taken (FDA 2018). However, there is some evidence that this recommendation should be relaxed (Palmer 2018). If tramadol is used, the baby should be watched for increased sleepiness, difficulty breastfeeding, and breathing difficulties or limpness.