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Pyrimethamine use while Breastfeeding

Medically reviewed by Last updated on Jan 11, 2022.

Drugs containing Pyrimethamine: Fansidar, Daraprim

Pyrimethamine Levels and Effects while Breastfeeding

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 of sulfadoxine and pyrimethamine.[1] It has been suggested that maternal pyrimethamine clearance might be increased during lactation, but data are insufficient to make a definitive conclusion.[2][3]

Drug Levels

Maternal Levels. Pyrimethamine milk 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.[4][5]

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.[6]

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.[5] 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.[4]

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.[7] No adverse effects were reported in any of the infants.

Effects on Lactation and Breastmilk

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


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. [PMC free article: PMC1765922] [PubMed: 16772000]
Salman S, Davis TME. Regarding "Lactation Status and Studies of Pyrimethamine Pharmacokinetics in Pregnancy". CPT Pharmacometrics Syst Pharmacol. 2017;6:730. [PMC free article: PMC5702900] [PubMed: 29064165]
de Kock M, Tarning J, Barnes KI, Denti P. Response to "Lactation Status and Studies of Pyrimethamine Pharmacokinetics in Pregnancy". CPT Pharmacometrics Syst Pharmacol. 2017;6:731. [PMC free article: PMC5702899] [PubMed: 29052341]
Clyde DF. An examination of factors involved in the transfer of pyrimethamine in human milk. East Afr Med J. 1957;34:81-5. [PubMed: 13437933]
Clyde DF, Press J, Shute GT. Transfer of pyrimethamine in human milk. J Trop Med Hyg. 1956;59:277-84. [PubMed: 13385913]
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. [PMC free article: PMC1401222] [PubMed: 3567020]
Clyde DF. Prolonged malaria prophylaxis through pyrimethamine in mothers' milk. East Afr Med J. 1960;37:659-60. [PubMed: 13694157]

Substance Identification

Substance Name


CAS Registry Number


Drug Class

  • Breast Feeding
  • Lactation
  • Anti-infective Agents
  • Antiparasitic Agents
  • Antimalarials
  • Antiprotozoal Agents

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Further information

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