Drug Levels and Effects:

Summary of Use during Lactation:

No adverse reactions in breastfed infants have been reported and it is acceptable in nursing mothers. In HIV-infected women, elevated viral HIV loads in milk were decreased after treatment with chloroquine to a greater extent than other women who were treated with the combination ofsulfadoxineand pyrimethamine .[1]

Drug Levels:

Maternal Levels.

Pyrimethaminemilk levels have been reported after doses of 25, 50 or 75 mg in 16 women. Milk levels ranged from 2.7 to 3.3 mg/L at 6 hours after the dose, 1.6 to 2 mg/L at 24 hours after the dose, and 0.66 to 1 mg/L at 48 hours after the dose (3 women only). Reported milk levels were not proportional to the dose in this old study using an antiquated assay method.[2][3]

Three women were given a single dose of pyrimethamine 12.5 mg orally 2 to 5 days postpartum. Milk samples were obtained periodically for about 9 days after the dose. Assuming a daily intake of 1 L of milk, the infants would receive 0.14, 0.21 and 0.34 mg in milk over the study period. The authors calculated that these values equated to an average of 30% (range 16.8 to 45.6%) of the maternal weight-adjusted dosage.[4]

Infant Levels.

Relevant published information was not found as of the revision date.

Effects in Breastfed Infants:

Administration of pyrimethamine to mothers of 26 predominantly breastfed infants 2 to 6 months old who were infected with malaria was curative in the infants.[3] The regimen consisted of 75 mg followed by a subsequent dose of 50-75 mg 4 to 7 days later. The efficacy apparently is related to breastfeeding habits, because infants in another tribal group who breastfed their infants less extensively were not protected.[2]

A case report indicates that a maternal dose of 75 mg orally followed by 25 mg weekly cured malaria in her breastfed infant and protected her infant against becoming infected with malaria for 6 months. After the mother missed taking her dose for 2 weeks, the infant developed symptoms of malaria.[5] No adverse effects were reported in any of the infants.

Possible Effects on Lactation:

Relevant published information was not found as of the revision date.


1. Semrau K, Kuhn L, Kasonde P et al. Impact of chloroquine on viral load in breast milk. Trop Med Int Health. 2006;11:800-3. PMID:16772000
2. Clyde DF. An examination of factors involved in the transfer of pyrimethamine in human milk. East Afr Med J. 1957;34:81-5. PMID:13437933
3. Clyde DF, Press J, Shute GT. Transfer of pyrimethamine in human milk. J Trop Med Hyg. 1956;59:277-84. PMID:13385913
4. Edstein MD, Veenendaal JR, Newman K et al. Excretion of chloroquine, dapsone and pyrimethamine in human milk. Br J Clin Pharmacol. 1986;22:733-5. PMID:3567020
5. Clyde DF. Prolonged malaria prophylaxis through pyrimethamine in mothers' milk. East Afr Med J. 1960;37:659-60. PMID:13694157

Substance Identification:

Substance Name:


CAS Registry Number:


Drug Class:

  • Antimalarials

  • Administrative Information:

    LactMed Record Number:


    Last Revision Date:

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