Medications and Lactation: What PNPs Need to Know

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

J Pediatr Health Care. 2003;17(6)

Lipid Solubility of the Drug and Fat Content of Milk

Lipid-soluble drugs readily diffuse across cell membranes by dissolving in the lipid bilayer. Almost without exception, a medication that is more lipid-soluble will transfer more quickly, and in greater amounts,into breast milk than one that is less lipid-soluble (Riordan & Auerbach, 1998). Water-soluble drugs must pass through pores to cross cell membranes, a process that slows diffusion. Since medications with low lipid solubility and those that are water-soluble diffuse slowly into breast milk, they are preferred for use in breastfeeding mothers (Banta-Wright, 1997).

Colostrum is low in lactose and fat and high in protein. The reverse is true of mature milk. Because mature milk has a higher fat content than colostrum, a lipid-soluble drug given during the late postpartal period will appear in breast milk at a higher levelthan if it had been given in the early postpartal period (Auerbach, 1999). However, even mature milk has a low proportion of fat to total milk volume and probably allows only a small amount of a medication to reach the infant (Banta-Wright, 1997).

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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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