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Mefloquine Pregnancy and Breastfeeding Warnings

Medically reviewed by Last updated on Dec 2, 2022.

Mefloquine is also known as: Lariam

Mefloquine Pregnancy Warnings

This drug should be used during pregnancy only if clearly needed and the benefit outweighs the risk.
-According to some authorities: Use is considered acceptable.

AU TGA pregnancy category: B3
US FDA pregnancy category: B

-The use of this drug to treat malaria or as chemoprophylaxis in high-risk situations is considered acceptable since the risk to the fetus is outweighed by the benefits to the mother and fetus.
-According to some authorities: For use during pregnancy, current guidelines (national and international) should be consulted.

Animal studies have revealed evidence of embryotoxicity and teratogenicity. Doses similar to the clinical acute treatment dose of 21 to 25 mg/kg (based on body surface area comparisons) were administered to pregnant mice, rats, and rabbits; at these maternally-toxic doses, embryotoxicity was observed in mice and rabbits and central nervous system effects (e.g., exencephaly, hydrocephaly, partially missing medulla oblongata) and craniofacial malformations were observed in mice, rats, and rabbits. This drug crosses the placenta and is detectable in fetal circulation. Data from published studies in pregnant women have shown no increase in the risk of teratogenic effects or adverse pregnancy outcomes after treatment or prophylaxis with this drug during pregnancy.

Published data on use of this drug during pregnancy include randomized controlled trials, intervention trials, prospective and retrospective cohort studies, and case series. These data showed that pregnant women who took this drug at various doses for both prevention and treatment of malaria did not have an increased risk of teratogenic effects or adverse pregnancy outcomes compared to the background rate in the general population. These data include more than 700 first trimester exposures to this drug and over 2000 second and third trimester exposures.

According to the US CDC, chloroquine is considered the drug of choice for malaria prophylaxis during pregnancy for women traveling to areas where chloroquine-resistant Plasmodium falciparum has not been reported; for travel to areas where chloroquine resistance is present, this drug is the only medication recommended for malaria prophylaxis during pregnancy.

Malaria in pregnant women may be more severe than in nonpregnant women and increases the risk for adverse pregnancy outcomes (including spontaneous abortion, stillbirth, prematurity). Women of childbearing age who are traveling to endemic malarious areas should be warned against becoming pregnant and to use effective contraception during prophylaxis and for at least 3 months afterwards. However, unplanned pregnancy during use of this drug is not an indication for terminating the pregnancy.

AU TGA pregnancy category B3: Drugs which have been taken by only a limited number of pregnant women and women of childbearing age, without an increase in the frequency of malformation or other direct or indirect harmful effects on the human fetus having been observed. Studies in animals have shown evidence of an increased occurrence of fetal damage, the significance of which is considered uncertain in humans.

US FDA pregnancy category B: Animal reproduction studies have failed to demonstrate a risk to the fetus and there are no adequate and well-controlled studies in pregnant women.

See references

Mefloquine Breastfeeding Warnings

In 1 study in a few subjects, low levels (3% to 4%) of this drug were excreted into human milk after a dose equal to 250 mg of the free base.

At 2 to 3 days postpartum, 2 women were given 250 mg orally. Milk samples were provided periodically by 1 woman for 56 days; milk drug level declined from 53 to 32 mcg/L over this period. The half-life in breast milk for the 2 women averaged 16.6 days. According to author estimation, an exclusively breastfed infant would receive 3.8% (average) of the maternal weight-adjusted dose after a single dose; however, due to accumulation, this value could be higher with weekly doses.

According to the US CDC, the very small amounts of antimalarial drugs transferred in breast milk are insufficient to provide adequate protection against malaria. If prophylaxis is required, infants should receive recommended doses of antimalarial drugs. Because this drug may be safely prescribed to infants, it is also safe for infants to be exposed to the small amounts excreted in breast milk. Current guidelines should be consulted for additional information.

Use is considered acceptable; caution is recommended.
-According to some authorities: As a precaution, use should be avoided.

Excreted into human milk: Yes (small amounts)

-The amount of drug in breast milk is not enough to harm a nursing infant.
-According to some authorities: For use in nursing mothers, current guidelines (national and international) should be consulted.

See references

References for pregnancy information

  1. "Product Information. Lariam (mefloquine)." Roche Laboratories (2002):
  2. Subramanian D, Moise KJ Jr, White AC Jr "Imported malaria in pregnancy: report of four cases and review of management." Clin Infect Dis 15 (1992): 408-13
  3. Bangchang KN, Davis TME, Looareesuwan S, White NJ, Bunnag D, Karbwang J "Mefloquine pharmacokinetics in pregnant women with acute falciparum malaria." Trans R Soc Trop Med Hyg 88 (1994): 321-3
  4. Samuel BU, Barry M "The pregnant traveler." Infect Dis Clin North Am 12 (1998): 325
  5. Nosten F, Vincenti M, Simpson J, Yei P, Thwai KL, deVries A, Chongsuphajaisiddhi T, White NJ "The effects of mefloquine treatment in pregnancy." Clin Infect Dis 28 (1999): 808-15
  6. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  7. Cerner Multum, Inc. "Australian Product Information." O 0
  8. Freedman DO "Clinical practice. Malaria prevention in short-term travelers." N Engl J Med 359 (2008): 603-12
  9. Arguin PM, Tan KR "Infectious Diseases Related to Travel. Malaria." (2015):
  10. CDC. Centers for Disease Control and Prevention "Guidelines for Treatment of Malaria in the United States." (2015):
  11. Melbourne: Therapeutic Guidelines Limited "eTG complete [Online]" (2015):

References for breastfeeding information

  1. Edstein MD, Veenendaal JR, Hyslop R "Excretion of mefloquine in human breast milk." Chemotherapy 34 (1988): 165-9
  2. "Product Information. Lariam (mefloquine)." Roche Laboratories (2002):
  3. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  4. Cerner Multum, Inc. "Australian Product Information." O 0
  5. United States National Library of Medicine "Toxnet. Toxicology Data Network." (2013):
  6. Arguin PM, Tan KR "Infectious Diseases Related to Travel. Malaria." (2015):
  7. Melbourne: Therapeutic Guidelines Limited "eTG complete [Online]" (2015):

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.