Medications and Lactation: What PNPs Need to Know

Jennifer M. Marks, BS; Diane L. Spatz, PhD, RNC

J Pediatr Health Care. 2003;17(6)

Protein-Binding of the Drug in Maternal Plasma

The foremost parameter that determines the degree of drug penetration into breast milk is plasma protein-binding (Hale, 2002). Drugs circulate in maternal plasma either bound to the plasma protein, albumin, or remain freely soluble in the plasma. The protein-bound fraction stays in the maternal circulation, while the medication fraction that is unbound can be transferred into human milk. Since more than half of maternal plasma protein is albumin, high protein-binding effectively restricts many drugs to maternal plasma and prevents their transfer into breast milk (Banta-Wright, 1997). The higher the percentage of protein-binding, the less likely the drug is to enter maternal milk (Hale, 2002). Thus, highly protein-bound drugs (e.g., warfarin) are excreted into the breast milk in low amounts and this reduces the possibility of the infant's exposure to the medication (Hale, 2002). A drug is considered significantly protein-bound if its binding to protein is greater than 90% (Hale, 2002).

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Abstract and Introduction
Protein-Binding of the Drug in Maternal Plasma
Maternal Plasma Concentrations
Breast Milk pH
Lipid Solubility of the Drug and Fat Content of Milk
Molecular Weight of the Drug
Drug Half-Life
Oral Bioavailability to the Infant
Evaluation of the Infant
Where to Seek Appropriate Information
Summary
Sidebar: Box. Drug Information Data Included in Medications and Mother's Milk (Hale, 2002)

Table. Drug information resources
Source	Contact Information
The Lactation Center	University of Rochester Medical Center 585-275-0088
Crozer-Chester Medical Center Drug Information Center	One Medical Center Boulevard Upland, PA 19013 610-447-2851
Brigham and Women's Hospital Boston, MA	617-732-5500; ask for clinical pharmacologist
Drugs in Lactation Web site (Hale)	www.neonatal.ttuhsc.edu/lact
Hale, T. W. (2002). Medications and Mother's Milk (10th ed.). Amarillo, TX: Pharmasoft	Ordering information: Pharmasoft Publishing Single copies $24.95, plus shipping 21 Tascocita Circle Amarillo, TX 79124-7301; tel: 800-378-1317; fax: 806-376-9901; www.iBreastfeeding.com
Drug Topics Red Book (106th ed.) (2002). Montvale, NJ: Medical Economics	Ordering information: www.medecbookstore.com
Briggs, G. G., Freeman, R. K., & Yaffe, S. J. (2002). Drugs in Pregnancy and Lactation (6th ed.)	Ordering information: Lippincott Williams & Wilkins, 530 Walnut Street Philadelphia, PA 19106

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