Transmission of medication from mother to baby

When a mother takes a medication such as an anti-depressant medication, there is a risk that the drug will be transfered to the infant through the breast milk. The amount of drug that is excreted into the milk depends on many factors. Transfer into human milk occurs when the concentration in maternal plasma is high. Information about absorption and when peak levels of a medication will occur are available. Nursing mothers are usually encouraged to take medications after nursing to avoid nursing when the medication is at its peak.  Drugs with a a low molecular weight pass easily into milk. Heparin is a large molecule compound and never passes into breast milk so it is safe for breast feeding mothers to use. Drugs with low protein binding capabilities do not bind to proteins in the mothers circulation and therefore pass easily into milk. One of the most important factors to consider in the transfer of medications to breast milk is the oral bioavailability. The drug must be easily absorbed in the mothers gut in order for it to reach her blood circulation and then cross into her milk. The baby also must absorb the medication from the mothers milk. Some drugs are destroyed in the infant’s gut or fail to be absorbed through the gut wall. Drugs enter milk primarily by diffusion. They pass from the maternal plasma through capillary walls into the alveolar cells lining alveolus. Medications must generally pass through both lipid membranes and the alveolar cell to penetrate milk. The most critical factor for drug penetration into a mothers milk is the level of the mothers plasma level. When the plasma level of a mother rises the concentration in milk increase as well. Drugs enter and exit milk mainly as a function of the mother’s plasma level (Hale, 2006). All medications are metabolized in the liver. Preterm or young infants have immature liver function which can delay the breakdown of medications and keep high circulating levels of drug


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