In addition to the parameters of the drug and the dose in mother's serum, and the amount in the milk, the characteristics of the infant are essential. The most important is the age and maturity of the infant, because the infant's ability to absorb, metabolize, and excrete the drug are dependent on this. Therefore, medications in the milk are of greater concern in the first few days of life than they will be at a week, a month or a year of age. For example, when a mother is taking a medication that is poorly excreted by a neonate, such as
3.4 Milk plasma ratio aminophylline, it may be well excreted by a 1-year-old and is not accumulated.
Absorption from the infant's gastrointestinal tract is dependent on the bioavailability of the drug, the effect of gastric pH and gastric enzymes, and the presence of food, which may impair absorption. Obviously, drugs in breast milk are present with food. If a medication can be given directly to an infant (for example, acetaminophen), it can be given to the nursing mother. Infants tolerate acetaminophen very well, detoxifying it in the sulfhydryl pathway rather than the glucuronidase pathway.
Infants' liver and kidneys are immature at birth. Thus, a drug that depends on liver metabolism, such as sulfadiazine, will compete with the bilirubin metabolism. A drug such as aspirin competes for albumin-binding sites in the infant, displacing bilirubin in the first month of life. However, clinical relevance may be questionable, due to the small amounts of a drug transferred via breast milk. In the case of aspirin, it is salicylic acid that passes into the milk and not acetyl-salicylic acid; thus, it does not interfere with platelets in the infant.
Renal excretion is also immature early in life and a drug that depends on renal excretion, such as caffeine, theophylline, and some antibiotics, will accumulate in the infant in the first weeks and months of life but will gradually be better tolerated as the infant excretes it more effectively. These same drugs when given to an infant directly are given less frequently (daily instead of twice daily) in the first week of life.
Was this article helpful?
If you suffer with asthma, you will no doubt be familiar with the uncomfortable sensations as your bronchial tubes begin to narrow and your muscles around them start to tighten. A sticky mucus known as phlegm begins to produce and increase within your bronchial tubes and you begin to wheeze, cough and struggle to breathe.