Topical Drugs in Nursing Mothers

Dosage Forms

Concern about the composition of “inert” ingredients in topical products applied to the nipples of nursing mothers was first raised in 2003. ¹ Most humans have mineral oil paraffins (i.e., petrolatum and Vaseline) in their bodies, thought to be obtained, in part, from cosmetic products. Because these hydrocarbons are not metabolized, they accumulate in the body fat. Lactating women excrete these chemicals into breast milk and their concentration in milk is highly correlated with the amounts in maternal body fat. ² Although there is little that can be done to decrease their excretion into milk, the use of petrolatum-containing ointments on the nipples potentially exposes infants to much larger amounts. Although the toxicological consequences of paraffin accumulation in the body are unclear, it is prudent to limit infant exposure by avoiding the use of ointments on the nipples. In general, water-miscible products are preferred over ointments for use on the nipples. In order of preference, solutions generally have the fewest “inert” ingredients of concern, followed by gels and creams. Lanolin is similar to an ointment, but it is not a hydrocarbon. It is a mixture of fatty acid esters that can be metabolized by the infant. Lanolin is not a concern for application to the breast area as long as a highly purified form is used and neither the mother nor the infant is allergic to wool.

Antibacterials

Topical iodine and povidone–iodine applied to the mother's skin can present a risk to the nursing infant. The concentration of iodine in these products is so high that even the small fraction that is absorbed can increase breast milk iodine concentration and cause transient hypothyroidism in breastfed infants, especially in geographic areas that are iodine deficient. Maternal exposure to povidone–iodine near term can also interfere with newborn thyroid screening tests. Numerous studies and case reports have documented these effects, and are, in fact, among the best documented adverse reactions in infants to substances in breast milk.^3,4 If used, maternal exposure should be minimized by using lower concentrations of povidone–iodine, applying it to the smallest possible surface area of the body, shortening contact time, and avoiding repeated applications. Iodine absorption can be particularly extensive with vaginal use and nursing mothers should avoid douching with povidone–iodine or use of iodine-containing tampons during breastfeeding. Mothers should also avoid application of iodine products to open wounds.

Topical chlorhexidine is a safer alternative to povidone–iodine and has been studied as a prophylaxis for discomfort and nipple trauma applied directly to the breasts. No obvious side effects occurred in infants; however, a systematic review concluded that application to the breasts is not justified based on current evidence. ⁵

Most of the commonly used topical antibacterials such as bacitracin, mupirocin, neomycin, and polymyxin B are poorly absorbed orally and can be used on the nipples as creams. Theoretically they might disrupt the infant's gastrointestinal microbiome, but this has not been studied. Clindamycin and erythromycin are orally absorbable, but can be used away from the breasts for acne.

Neither topical nor vaginal metronidazole has been studied during breastfeeding. After vaginal and topical administration, maternal plasma levels are only 1–2% of those after typical oral doses, so are unlikely to affect the breastfed infant.

Antifungals

Most common topical antimycotic agents present no hazard to infants even if they ingest small amounts. Nystatin and amphotericin B are not absorbed orally. Clotrimazole and miconazole are absorbed, but extensively metabolized by the liver, so they do not reach the systemic circulation. In fact, these drugs are formulated as oral gels in some countries outside the United States for application directly to the infant's mouth to treat thrush. Ketoconazole is potentially hepatotoxic if ingested, so it should not be used on the breast. Use of ketoconazole shampoo or topical use on the skin away from the breast by the mother poses little or no risk to the breastfed infant. Other drugs in this class are mostly intended for vaginal use and little is known about their oral absorption. Topical drugs for tinea infections present little risk when applied to the nails.

Gentian violet is potentially toxic to the mucous membranes, causing ulceration, and potentially tattooing the skin. It is mutagenic and carcinogenic in rodents, and occasionally causes allergic sensitization, with cross-reactions to other dyes. Academy of Breastfeeding Medicine guidelines for treating Candida infection of the nipples state that an aqueous solution of gentian violet of <0.5% can be used for not >7 days on the nipple. ⁶ However, much safer alternatives already noted are available and gentian violet should be considered a last resort.

Insecticides and Repellants

Many drugs used for lice and scabies are environmental contaminants and can be found in breast milk. Nevertheless, treatment of these infestations often requires their use. Because <2% is absorbed after topical application of pyrethrins and permethrin, their rapid metabolism to inactive metabolites, and safe application directly on infants' skin, these products are acceptable in nursing mothers. Malathion appears to be poorly absorbed after topical application for lice, but, until more data become available, other agents are preferred. ⁷

No information is available on the clinical use of spinosad during breastfeeding, but it is not systemically absorbed after topical application, so it should not be present in breast milk. The topical suspension contains benzyl alcohol. High doses of benzyl alcohol are potentially toxic to neonates, and the manufacturer states that mothers concerned about benzyl alcohol could pump and discard breast milk for 8 hours. This is probably unnecessary because it is very unlikely that amounts used in the treatment of head lice reach toxic levels in breast milk.

Sulfur 5–10% in a petrolatum base is safe for topical use in infants <2 months of age. ⁸ This makes it a useful alternative to organic insecticides for nursing mothers with scabies; however, the petrolatum base makes it undesirable for use on the breast.

Topical application of lindane by mothers can increase lindane levels in milk for at least several days. It is a persistent environmental contaminant, and possibly has estrogenic effects that could decrease lactation as well as affect the nursing infant. Lindane should not be used during breastfeeding. ⁸

Although little information on their excretion into breast milk is available, insect repellants are generally not of concern during breastfeeding. These include diethyltoluamide (DEET), icaridin (picaridin), oil of lemon eucalyptus, and IR3535. ⁹

Anti-Inflammatory Drugs

Topical corticosteroids have not been well studied during breastfeeding. Since only extensive application of the most potent corticosteroids can cause systemic effects in the mother, it is unlikely that short-term maternal application of topical corticosteroids would pose a risk to the breastfed infant by passage into breast milk. It is particularly important to ensure that the infant's skin does not come into direct contact with the areas of skin that have been treated with high-potency products.

Application of corticosteroids to the breast and nipples can be problematic. In one case report, a topical corticosteroid applied to the mother's nipples resulted in prolonged QT interval, cushingoid appearance, severe hypertension, decreased growth, and electrolyte abnormalities in her 2-month-old breastfed infant. The mother had used the cream since birth for painful nipples. ¹⁰ Only the lower potency corticosteroids (e.g., hydrocortisone and triamcinolone) should be used on the nipple or areola where the infant could directly ingest the drugs from the skin. High potency corticosteroids (e.g., betamethasone and clobetasol) should be avoided on the nipples.^11,12

Topical tacrolimus and pimecrolimus have not been studied well, but appear to present a low risk to the nursing infant because they are poorly absorbed after topical application. If the breast is to be treated, other drugs are preferred.^7,11

Calcipotriene and tazarotene are two topical agents for psoriasis. Calcipotriene is probably a low risk to the nursing infant and is generally considered acceptable during breastfeeding, even to the nipple area, but application of the combination product containing betamethasone (Enstilar) should be avoided. Tazarotene is not contraindicated during breastfeeding; however, some experts feel it should not be used on >20% of the body surface area while nursing because of possible absorption.^7,11

Miscellaneous Topical Products

Coal tar applied topically to maternal skin can result in detectable pyrene metabolites in infant urine, probably by skin-to-skin or skin-to-mouth contact with the mother. Because of the potential toxicity of coal tar to the breastfed infant, other drugs are preferrable. ⁷

Topical use of nitroglycerin for anal fissures by nursing mothers appears to have no adverse effects on their breastfed infants. Nitroglycerin application to the nipples has been used for alleviation of Raynaud phenomenon of the nipples, but only after cessation of breastfeeding.

Questions about the use of hair products are often raised by mothers. Exposure to them is brief and on a limited surface area. No evidence exists that hair bleaches, dyes, or straighteners have any harmful effect on the nursing infant.