Mefloquine (Lariam) — Malaria Prevention Guide for US Travelers
A physician-reviewed guide to mefloquine for Americans traveling to malaria-endemic regions
Mefloquine carries an FDA black box warning for serious neuropsychiatric adverse effects including anxiety, hallucinations, depression, unusual behavior, and suicidal ideation. These effects may persist long after the drug is stopped — in some cases permanently. Discuss your full medical and psychiatric history with your physician before taking mefloquine.
What is Mefloquine (Lariam)?
Mefloquine (brand name Lariam) is a prescription antimalarial medication used to prevent and treat malaria in travelers to endemic regions. It was developed by the US Army in the 1970s and approved by the FDA in 1989. While effective against Plasmodium falciparum — the most dangerous malaria species — mefloquine has become a second-line option for many travelers due to its potential for serious neuropsychiatric side effects. It is available only by prescription in the United States and requires careful pre-travel medical screening.
How Does Mefloquine Work?
Mechanism of Action
Mefloquine is a blood schizonticide — it acts on the blood stage of the malaria parasite's life cycle. After a mosquito bite introduces Plasmodium parasites into the bloodstream, they invade red blood cells and multiply. Mefloquine disrupts this process by interfering with the parasite's ability to metabolize hemoglobin, ultimately killing the parasite inside the red blood cell before it can cause symptoms.
Unlike doxycycline and atovaquone/proguanil (Malarone), which also act on the liver stage, mefloquine only kills the blood-stage parasite. This is why it must be continued for 4 full weeks after leaving a malaria zone — to eliminate any parasites that may have entered the bloodstream near the end of the trip and are still developing.
Dosing Schedule for US Travelers
Before Travel
Start mefloquine 2–3 weeks before departure. Take one tablet (250 mg) by mouth once per week on the same day each week. Take with food and a full glass of water to reduce GI side effects.
During Travel
Continue taking one tablet once weekly on the same day of the week throughout your entire stay in the malaria-endemic area. Do not skip doses or change the day of the week.
After Return
Continue for 4 full weeks after leaving the malaria-endemic area. This is critical — stopping early leaves you unprotected against parasites that may already be in your bloodstream.
Adult Dose
Standard adult dose: 250 mg (one tablet) once weekly. Pediatric dosing is weight-based — consult your physician. Available as 250 mg scored tablets which can be crushed and mixed with food for children.
Pick a Consistent Day
Choose a day of the week and always take your dose on that day. Many travelers choose to start on a Saturday or Sunday so any initial side effects occur over the weekend when they can monitor closely before going to work.
Take With Food
Always take mefloquine with food and at least 8 oz of water. Taking it on an empty stomach significantly increases nausea and vomiting. Avoid taking at bedtime if you experience vivid dreams or sleep disturbances.
Side Effects & Risks
The most serious concern with mefloquine is its potential to cause neuropsychiatric reactions. These can range from mild (vivid dreams, anxiety) to severe (hallucinations, psychosis, suicidal behavior). In some cases these effects have been permanent. Any traveler experiencing psychological or neurological symptoms should stop mefloquine immediately and seek medical care. Do not wait until returning home.
Neuropsychiatric Effects
Vivid or disturbing dreams, insomnia, anxiety, depression, mood changes, confusion, hallucinations, paranoia, aggression, and in rare cases suicidal ideation or psychosis. May begin during treatment or after stopping the drug. Can persist for months or longer.
Gastrointestinal Effects
Nausea, vomiting, diarrhea, and abdominal pain are common — especially in the first few doses. Usually manageable by taking mefloquine with food. Severe GI symptoms that persist are a reason to contact your physician.
Neurological Effects
Dizziness, headache, tinnitus (ringing in the ears), and balance problems. Rarely: seizures. If you experience loss of balance, ringing in the ears, or seizure activity, stop the drug and seek immediate medical attention.
Cardiovascular Effects
Mefloquine can cause changes in heart rhythm (QT interval prolongation). It should be used with extreme caution in travelers with heart conditions, arrhythmias, or those taking other medications that affect heart rhythm. Discuss with your cardiologist if relevant.
Visual Disturbances
Some users report blurred vision or visual changes. Avoid activities requiring fine visual coordination or precise balance (such as scuba diving or operating heavy machinery) until you know how mefloquine affects you personally.
Stop and Seek Care If:
You develop anxiety, depression, restlessness, confusion, hallucinations, suicidal thoughts, seizures, or loss of balance. Do not wait to return home. These are warning signs of serious neuropsychiatric toxicity. Tell your doctor you are taking mefloquine.
Before prescribing mefloquine, your travel medicine physician should screen for a personal or family history of psychiatric illness (depression, anxiety disorders, schizophrenia, bipolar disorder), seizure disorders, cardiac arrhythmias, and hypersensitivity to quinoline antimalarials. These conditions are contraindications or relative contraindications to mefloquine use. Be honest and complete with your medical history — do not minimize past mental health episodes.
Who Should NOT Take Mefloquine
Psychiatric History
Anyone with a current or past history of depression, anxiety disorders, schizophrenia, bipolar disorder, psychosis, or any other serious psychiatric condition. This is an absolute contraindication.
Seizure Disorders
Anyone with a history of epilepsy or seizures. Mefloquine lowers the seizure threshold and can trigger seizures in susceptible individuals. An alternative antimalarial must be used.
Cardiac Conduction Disorders
Anyone with a known cardiac arrhythmia or conduction abnormality (including QT prolongation, heart block, or those on antiarrhythmic drugs). Mefloquine can worsen these conditions.
Hypersensitivity
Anyone with a known allergy or hypersensitivity to mefloquine, quinine, quinidine, or related compounds. Cross-reactivity within the quinoline class is documented.
Certain Occupations
Not recommended for pilots, divers, or individuals in precision-critical occupations due to the risk of dizziness, balance disturbance, and visual effects that could impair performance and safety.
First Trimester Pregnancy
Generally avoided in the first trimester of pregnancy. May be considered in second and third trimesters if travel to high-risk areas is unavoidable and no safer alternative is appropriate — discuss thoroughly with your OB-GYN and travel medicine physician.
Mefloquine vs Other Antimalarials
Three prescription antimalarials are recommended by the CDC for travel to chloroquine-resistant malaria regions including sub-Saharan Africa, Southeast Asia, and South America. Your travel medicine physician will help select the most appropriate option.
Atovaquone/Proguanil (Malarone)
Dosing: Daily. Start 1–2 days before, continue 7 days after.
Advantages: Well-tolerated, minimal side effects, short post-travel course, suitable for most travelers.
Disadvantages: More expensive. Must be taken daily.
Dosing: Daily. Start 1–2 days before, continue 28 days after.
Advantages: Inexpensive, widely available, also covers other infections.
Disadvantages: Sun sensitivity, GI upset, not for pregnant women or children under 8.
Mefloquine (Lariam) — This Article
Dosing: Weekly. Start 2–3 weeks before, continue 4 weeks after.
Advantages: Once weekly, convenient for long trips, inexpensive.
Disadvantages: FDA black box warning, neuropsychiatric risk, many contraindications.
Drug Interactions
Antiarrhythmics & Beta Blockers
Mefloquine combined with antiarrhythmic drugs (amiodarone, flecainide) or beta blockers may increase risk of dangerous heart rhythm abnormalities. Avoid concurrent use unless specifically cleared by a cardiologist.
Psychiatric Medications
Concurrent use with antidepressants, antipsychotics, or other CNS-active drugs may potentiate neuropsychiatric side effects. This combination should generally be avoided. Discuss all mental health medications with your physician.
Anticonvulsants
Mefloquine may reduce the effectiveness of anticonvulsant medications (valproic acid, carbamazepine, phenytoin) by lowering their blood levels. This is a contraindication — individuals on anticonvulsants should use a different antimalarial.
Typhoid Vaccine (Oral)
Mefloquine may reduce the effectiveness of the oral typhoid vaccine (Vivotif). Complete the full oral typhoid vaccine series at least 3 days before starting mefloquine. The injectable typhoid vaccine is not affected.
Quinine & Quinidine
Do not take mefloquine together with quinine or quinidine (used to treat malaria or leg cramps). The combination significantly increases the risk of seizures and cardiac arrhythmias. If treating breakthrough malaria, wait at least 12 hours after quinine before starting mefloquine.
Alcohol
Avoid alcohol while taking mefloquine. Alcohol can worsen CNS side effects including dizziness, confusion, and impaired coordination, and may amplify the neuropsychiatric effects of the drug. This is especially important during the first few weeks of treatment.
Special Populations
Pregnancy
Mefloquine is generally avoided in the first trimester due to limited safety data. It may be used in the second and third trimesters when the risk of malaria is considered to outweigh the potential risks of the drug. Pregnant travelers should avoid high-risk malaria destinations when possible. Consult both your OB-GYN and a travel medicine physician.
Children
Mefloquine is approved for children weighing more than 5 kg (11 lbs). Dosing is weight-based. The tablet can be crushed and mixed with food. Neuropsychiatric side effects have been reported in children. Malarone is often preferred for children due to better tolerability and simpler dosing.
Older Adults
Older travelers may be more susceptible to dizziness and balance disturbances caused by mefloquine, increasing fall risk. Cardiovascular screening is particularly important in this population. Discuss carefully with your physician whether mefloquine is appropriate given your full health profile.
Breastfeeding
Mefloquine is excreted in small amounts in breast milk. The CDC considers it compatible with breastfeeding when the benefits outweigh the risks. However, infants should be monitored for side effects. Discuss with your physician and pediatrician before use while breastfeeding.
Liver Disease
Mefloquine is metabolized by the liver. Travelers with significant liver disease should use mefloquine with caution or avoid it entirely, as impaired metabolism can lead to drug accumulation and increased side effect risk. Malarone and doxycycline should be discussed as alternatives.
Long-Term Travelers
For expatriates and long-term travelers (months to years), mefloquine's weekly schedule can be convenient. However, prolonged use has been associated with cumulative neuropsychiatric risk. Schedule periodic check-ins with a physician if using mefloquine for extended periods. Annual review is recommended.
Getting a Mefloquine Prescription in the US
Travel Medicine Clinic
The preferred source for all antimalarial prescriptions. Board-certified travel medicine physicians perform pre-travel risk assessments, screen for contraindications, and provide destination-specific advice. Find a clinic at istm.org or via the CDC's travel clinic directory.
Primary Care Physician
Your PCP can prescribe mefloquine but may have less experience with travel-specific risk stratification. Bring a list of your destinations, planned activities, and trip duration. Ask specifically about the FDA black box warning and whether mefloquine is right for you.
Cost & Insurance
Generic mefloquine is significantly less expensive than brand-name Lariam. Cost is approximately $10–$30 per month for the generic. Many US insurance plans do not cover antimalarials for travel — check with your insurer. A travel medicine consultation may require a copay or out-of-pocket payment.
If You Develop Fever During or After Travel
No antimalarial is 100% effective. If you develop a fever of 38°C (100.4°F) or higher while in a malaria-endemic area or within one year of returning, seek emergency medical care immediately. Tell the treating physician you are taking mefloquine and provide your full travel history. Malaria can be fatal within 24–48 hours if untreated.
If you develop malaria while taking mefloquine prophylaxis, do not use mefloquine to treat the infection — use a different drug class. The treating physician must be informed that mefloquine was being used prophylactically, as this affects the choice of treatment regimen and the required interval between drugs.
Mefloquine Pre-Travel Checklist
- See a travel medicine physician at least 6–8 weeks before departure
- Disclose full psychiatric history — any history of depression, anxiety, or psychosis is a contraindication
- Disclose seizure history, cardiac conditions, and all current medications
- Confirm mefloquine is appropriate for your destination — check CDC destination pages
- Start mefloquine 2–3 weeks before departure — not the day before
- Take first dose on a weekend to monitor for side effects before returning to work
- Always take with food and a full glass of water
- Complete full oral typhoid vaccine series at least 3 days before starting mefloquine
- Avoid alcohol while taking mefloquine
- Know the warning signs: anxiety, depression, vivid dreams, confusion, hallucinations — stop and seek care if these occur
- Continue for 4 full weeks after leaving the malaria-endemic area
- Seek emergency care for any fever ≥38°C during or within one year after travel
- Purchase travel health insurance with medical evacuation coverage
- Also use physical mosquito protection: DEET ≥30%, long sleeves after dusk, permethrin-treated nets
