What Is Mefloquine? Uses, Dosage, and What You Need to Know in 2026

Mefloquine hydrochloride is an oral prescription antimalarial medication used to prevent and treat certain types of malaria. Originally developed by the U.S. military at the Walter Reed Army Institute of Research in the 1970s, it was first approved by the FDA in May 1989. The brand name Lariam, made by Roche, was withdrawn from the U.S. market in 2009, and only generic versions are now available domestically.

Mefloquine belongs to the class of drugs known as antimalarial quinolines — the same general class as quinine, the original malaria treatment. It is a 4-quinolinemethanol derivative and is chemically distinct from other antimalarials.

What Is Mefloquine Used For?

Mefloquine has two FDA-approved uses:

Malaria prevention (prophylaxis): Taken once weekly by travelers to malaria-endemic regions to prevent infection from Plasmodium falciparum (including chloroquine-resistant strains) and Plasmodium vivax.

Malaria treatment: Used to treat mild-to-moderate malaria caused by mefloquine-susceptible strains of P. falciparum or P. vivax. It is NOT recommended for severe malaria (IV antimalarials are required for severe cases).

Mefloquine is one of several antimalarials recommended by the CDC for travelers to most malaria-endemic regions worldwide. It is particularly helpful for those who cannot use atovaquone-proguanil or doxycycline, and for pregnant travelers to high-risk areas.

Important: Mefloquine is NOT recommended for travel to parts of Southeast Asia (particularly the Greater Mekong Subregion — Thailand-Myanmar border, Cambodia, Laos, Vietnam) where P. falciparum resistance to mefloquine is widespread.

Mefloquine Dosage: How Much Do You Take?

Mefloquine is available as 250 mg tablets. Dosing differs depending on whether you're taking it for prevention or treatment:

Prevention (adults): 250 mg (1 tablet) once weekly, on the same day each week. Start 1-3 weeks before travel. Continue during travel. Continue for 4 weeks after leaving the endemic area.

Treatment (adults): 1,250 mg (5 tablets) as a single oral dose. CDC recommends splitting: 750 mg, then 500 mg 6-12 hours later to reduce side effects.

Prevention (children): Weight-based weekly dosing for children 6 months and older. Not recommended for prophylaxis in children weighing less than 44 lbs (20 kg).

Treatment (children 6 months+): 20-25 mg/kg as a single dose (max 1,250 mg). Splitting into 2 doses 6-8 hours apart may reduce side effects.

How Should You Take Mefloquine?

Always take mefloquine with food — ideally your largest meal of the day — and with at least 8 oz (240 mL) of water. Food significantly improves absorption and reduces gastrointestinal side effects. Do NOT take it on an empty stomach.

If you can't swallow tablets, mefloquine can be crushed and mixed with water, milk, juice, applesauce, or another liquid. Take the mixture immediately after preparing.

For prophylaxis, take mefloquine on the same day each week. If you miss a dose, take it as soon as you remember — but if it's close to your next scheduled dose, skip the missed dose and take the next one on schedule. Never double up.

What Is Mefloquine's Half-Life?

Mefloquine has an unusually long half-life of approximately 3 weeks (about 15-33 days in different studies). This long half-life is what makes once-weekly dosing possible — the drug builds up to protective blood levels and stays in your system for weeks after each dose. It's also why you need to continue taking it for 4 weeks after leaving an endemic area: the drug takes time to clear, providing continued protection.

The downside of this long half-life: if you experience side effects, they can persist for weeks after your last dose. This is particularly relevant for the neuropsychiatric side effects that carry the drug's black box warning.

Key Warnings and Safety Information

Mefloquine carries an FDA black box warning — the most serious level — for neurological and psychiatric side effects including dizziness, loss of balance, tinnitus, anxiety, depression, hallucinations, paranoia, and suicidal thoughts. These effects can occur at any time during treatment and may persist for months to years or become permanent after stopping the drug.

Do NOT use mefloquine for prevention if you have a history of depression, anxiety disorder, psychosis, schizophrenia, or seizures.

Is Mefloquine Currently Available?

Mefloquine has faced documented supply limitations since May 2024. Not all pharmacies carry it in stock, and the shortage has affected availability nationwide. See: Why Is Mefloquine Hard to Find? If you need to locate mefloquine at a pharmacy near you, medfinder can call pharmacies on your behalf and send you the results by text.