Reviewed on 2/15/2022

What Is Mefloquine and How Does It Work?

Mefloquine is a prescription medication used for the prevention and treatment of mild-to-moderate acute malaria.

What Are Dosages of Mefloquine?

Adult and pediatric dosage


  • 250mg

Acute Malaria Infections

Adult dosage

  • 1250 mg orally once

Pediatric dosage

  • Children below 6 months old: Safety and efficacy not established
  • Children above 6 months old: 20-25 mg/kg orally as a single dose or may divide into 2 doses

Malaria Prevention

Adult dosage

  • 250 mg orally every week
  • Start 1-2 weeks before arrival in the endemic area; continue 4 weeks after leaving the endemic area

Pediatric dosage

  • Children weighing between 5 to 9 kg: 31.25 mg (1/8 tablet) orally every week
  • Children weighing between 10 to 19 kg: 62.5 mg (1/4 tablet) orally every week
  • Children weighing between 20 to 29 kg: 125 mg (1/2 tablet) orally every week
  • Children weighing between 30 to 45 kg: 187.5 mg (3/4 tablet) orally once every week
  • Children weighing above 45 kg: 250 mg (1 tablet) orally once every week
  • Start 1-2 weeks before arrival in the endemic area; continue 4 weeks after leaving the endemic area

Dosage Considerations – Should be Given as Follows: 

  • See “Dosages”

What Are Side Effects Associated with Using Mefloquine?

Common side effects of Mefloquine include:

  • stomach pain,
  • vomiting,
  • diarrhea,
  • dizziness,
  • muscle pain,
  • fever,
  • chills, and
  • mild skin rash 

Serious side effects of Mefloquine include:

  • sudden headache,
  • ringing in the ears,
  • dizziness,
  • loss of balance,
  • problems with coordination,
  • severe anxiety,
  • depression,
  • paranoia,
  • hallucinations,
  • confusion,
  • unusual behavior,
  • thoughts about suicide,
  • lightheadedness,
  • seizure,
  • severe headache,
  • blurred vision,
  • chest pain,
  • shortness of breath,
  • uneven heartbeats,
  • nausea,
  • upper stomach pain,
  • itching,
  • tiredness,
  • loss of appetite,
  • dark urine,
  • clay-colored stools, and
  • yellowing of the skin or eyes (jaundice

Rare side effects of Mefloquine include:

  • none 
This is not a complete list of side effects and other serious side effects or health problems that may occur as a result of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.

What Other Drugs Interact with Mefloquine?

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

  • Mefloquine has severe interactions with the following drug:
    • lefamulin
  • Mefloquine has serious interactions with at least 144 other drugs.
  • Mefloquine has moderate interactions with at least 133 other drugs.
  • Mefloquine has minor interactions with the following drugs:

This information does not contain all possible interactions or adverse effects. Visit the RxList Drug Interaction Checker for any drug interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions, concerns.

What Are Warnings and Precautions for Mefloquine?


Effects of drug abuse

  • None

Short-Term Effects

  • See “What Are Side Effects Associated with Using Mefloquine?”

Long-Term Effects

  • See “What Are Side Effects Associated with Using Mefloquine?”


  • In case of life-threatening, serious, or overwhelming malaria infections due to P. falciparum, patients should be treated with an IV antimalarial drug; following completion of IV treatment, mefloquine may be given to complete the course of therapy
  • May increase QT interval; caution with other drugs known to prolong QT interval; halofantrine or strong CYP3A4 inhibitors (e.g., ketoconazole) should not be administered concomitantly or within 15 weeks of the last dose of mefloquine due to risk of a potentially fatal prolongation of QTc interval
  • Transitory and clinically silent ECG alterations have been reported during therapy; alterations included sinus bradycardia, sinus arrhythmia, first-degree AV-block, and abnormal T waves; benefits of therapy should be weighed against the possibility of adverse effects in patients with cardiac disease
  • Caution with hepatic impairment
  • If the drug is to be administered for a prolonged period, periodic evaluations including liver function tests and evaluations for neuropsychiatric effects should be performed
  • Agranulocytosis and aplastic anemia reported
  • Geographical drug resistance patterns of P. falciparum occur, and the preferred choice of malaria prophylaxis might be different from one area to another
  • Periodic ophthalmic examinations recommended; retinal abnormalities seen in humans with long-term chloroquine use have not been observed with mefloquine use; however, long-term feeding of mefloquine to rats resulted in dose-related ocular lesions
  • Psychiatric and neurologic adverse effects
  • May cause neuropsychiatric adverse reactions, which may be difficult to identify in children, monitor for symptoms, especially in nonverbal children
  • Psychiatric symptoms ranging from anxiety, paranoia, and depression to hallucinations and psychotic behavior can occur; symptoms may occur early during mefloquine use, and in some cases, these symptoms have been reported to continue for months or years after mefloquine has been stopped
  • Cases of suicidal ideation and suicide have been reported
  • Should not be prescribed for prophylaxis in patients with active depression, generalized anxiety disorder, psychosis, schizophrenia, or other major psychiatric disorders
  • Dizziness or vertigo, tinnitus, and loss of balance reported; these symptoms were reported to be permanent in some cases
  • May increase the risk of convulsions in patients with epilepsy; prescribed only for curative treatment in such patients and only if there are compelling medical reasons for its use
  • Concomitant administration of mefloquine and quinine or chloroquine may increase the risk of convulsions
  • During prophylactic use, if symptoms emerge, discontinue and substitute treatment with a different antimalarial agent

Pregnancy and Lactation

  • May be acceptable during pregnancy 
  • Lactation
    • Minimally excreted in human breast milk; based on a study in a few subjects, low concentrations (3% to 4%) excreted; caution advised
Medscape. Mefloquine.

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