Drugs in Breast Milk

You might be concerned about certain drugs being transferred into your breast milk, and their effects on your baby.

Some ladies decide not to breastfeed at all, due to epilepsy or hyperthyroidism.

Some Mothers believe that it is better for their babies to drink formula and avoid the risk of these drugs entering into their breast milk.

There are actually very few medications that are contraindicated during breastfeeding and it is advised to first check the American Academy of Paediatrics, before deciding to wean. 

In the first week of a baby’s life, while the mother is still producing colostrum, it is important to remember that drug transfer into the breast milk, is much easier during this time and that the baby should be monitored closely. 

There are several factors that influence whether a certain drug will enter the breast milk more than another, if at all.

Risk Factors Include

  • Plasma concentration: Some drugs have a higher level of build up in the mother’s blood and these are more likely to be transferred into the breast milk. 
  • Molecule size: Drugs that have bigger molecules are less likely to pass through cell membranes and into the breast milk. 
  • Binding of proteins: Drugs that attach to proteins in the mother’s blood are less likely to pass into the breast milk. 
  • Fat solubility: Drugs that can dissolve in fat are more likely to pass into the breast milk and can be carried along with the fat in breast milk. 
  • Bioavailability: Drugs that are not taken orally by the mother (taken via injection, inhalation or cream), can sometimes have no effect on the baby when consumed orally via the breast milk. 
  • Half life of drug:  The time it takes for half the amount of this specific drug to leave the blood stream. Some drugs are used up quickly and then passed out in the urine and/or feces. 

Individual Risk Factors of Drug Safety 

  • There is low risk for babies who are older than 6 months old. Babies who are older, can get rid of toxins in their systems easier than younger ones and older babies also do not depend as much on breast milk for their entire nutritional requirements. 
  • There is a medium risk for those babies who are younger than 6 months and who have specific problems with their metabolisms or their guts. 
  • There is very high risk for those babies who are premature or sick, especially those with impaired kidney function. 

Drugs and Milk Supply

  • Certain drugs will decrease a mother’s milk supply, others may increase milk supply and then there are some that have no affect on supply. 
  • Not all women are going to react the same way to a specific drug and the reduction in milk supply may, in some cases, only be noticeable over time. 

Some drugs that are known to decrease milk production:

  • Alcohol.
  • Estrogens (often found in birth control pills).
  • Ergot Alkaloids (Bromocriptine & Cabergoline).
  • Progestogens.
  • Pseudoephedrine. 

Some drugs that are known to increase milk production:

  • Motilium (Domperidone) 
  • Reglan (Metoclopramide)
  • Risperidone.
  • Phenothiazine Neuroleptics.

Drug Safety while Breastfeeding

A list of some safe medication while breastfeeding

  • Acetaminophen / paracetamol (Tylenol and Panadol).
  • Ibuprofin (Advil, Nuprin, Motrin).
  • Dextromethorphan (active ingredient in Triaminic, Robitussin, Coricidin.)

A list of medication that is still safe, but not as safe as the above medication

  • Selective serotonin reuptake inhibitors (SSRIs) such as Sertraline (Zoloft) and Paroxetine (Paxil).
  • Bupivacaine (Marcaine).
  • Fentanyl.

A list of medication that is only moderately safe while breastfeeding

  • Aspirin
  • Codeine

Medications that are possibly harmful to the baby while breastfeeding

  • Lithium.

Medication that should never be taken while breastfeeding

  • Angiotensin-converting enzyme (ACE) inhibitors.
  • Radioactive isotopes.
  • Cocaine.

How to Minimize Drug Effects

  • If a medication has a short half life, the mother can avoid feeding her baby until the drug levels have lowered.
  • Mom can pump and dump milk during the times that she is taking risky medication, this is just to keep her milk supply up.
  • Choose medications that are less risky, ask about alternatives. Ask about paediatric approved medications. 
  • Ask about medications that have higher protein binding and those that are of larger molecular size. Also ask about medications that do not pass easily into the blood brain barrier if possible. 
  • Always keep an eye on the baby. Watch especially for drowsiness and gut problems. 

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Drug package inserts cannot to used to determine the safeness of a drug. Drug companies do not do studies that involve pregnant and breastfeeding women, and always ad a “not to be taken while pregnant or breastfeeding” on the package, just to protect themselves against lawsuits.

Here is a reliable resource for drug safety while breastfeeding

Tracy Behr, CBC, CLD (CBI)

Reference: Course information through Childbirth International on the physiology of breastfeeding / drugs in breast milk.

Other pages

- Social drugs and breastfeeding

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