The Breastfeeding Factor: Using Drugs While Breastfeeding

Factors Affecting Drug Safety
What makes one drug safer than another for a breastfeeding pair? Several different factors come into play here. Among them are characteristics of the drug, such as the drug's half-life, its protein-binding capacity, its lipid solubility, and its oral bioavailability.

A drug's half-life is the measure of how long the drug stays in your system. Different drugs are cleared from your body at different rates. The longer a drug lingers in your circulation before being processed by your liver and completely eliminated, the greater your baby's exposure will be through your milk. A drug with a shorter half-life is better for a nursing mother than one with a longer half-life. A drug with a longer half-life will actually build up in a baby's bloodstream over time. If a drug has a short half-life, you can schedule your dosages so that levels of the drug fall significantly in your body before your baby feeds again.

Protein-binding capacity is the degree to which the active ingredient in the drug joins with proteins in the body on a molecular level. A drug with a high protein-binding capacity – one that binds well with proteins in the mother's body – is safer, because only non-protein-bound drugs can pass into milk.

Lipid solubility is just what it sounds like: the ease with which a drug is absorbed into fats in the body. A drug that is more lipid-soluble is better absorbed into fats, so more of it can pass into a mother's milk.

A drug's oral bioavailability is its potential to be absorbed through the walls of the baby's gastrointestinal tract. This also is an important factor in the safety of a medication. Drugs with low oral bioavailability cannot pass through the intestinal walls into the baby's bloodstream, and just pass right out into the baby's diaper.

Occasional use of medications, when you really need them, should not stop you from breastfeeding your baby. If you have a chronic disease, such as rheumatoid arthritis, Graves' disease (an autoimmune disease that affects the thyroid), or epilepsy, and you have no choice but to use medications every day, you will need to work closely with your physician and your baby's pediatrician, but you should still be able to breastfeed for at least a few weeks. Even a few weeks' worth of mother's milk is better than none.