Lariam (mefloquine hydrochloride) is a prescription antimalarial medication indicated for the prophylaxis of Plasmodium falciparum and Plasmodium vivax malaria in travelers to areas with known chloroquine-resistant strains. As a long-acting chemoprophylactic agent, it offers robust protection against one of the world’s most dangerous parasitic infections. Its weekly dosing regimen provides convenience for extended travel, though its use requires careful medical supervision due to a distinct side effect profile. This expert review covers the essential pharmacological, clinical, and safety information necessary for informed prescribing and patient counseling.

Features

• Active ingredient: Mefloquine hydrochloride (250 mg tablet equivalent to 228 mg base)
• Formulation: Film-coated tablets for oral administration
• Pharmacological class: 4-Methanolquinoline antimalarial
• Half-life: Approximately 2-4 weeks, allowing for weekly dosing
• Spectrum: Effective against chloroquine-resistant P. falciparum and P. vivax
• Manufacturer: Originally developed by Hoffmann-La Roche; now available as generic

Benefits

• Provides highly effective prophylaxis against multidrug-resistant malaria strains in endemic regions
• Weekly dosing schedule enhances adherence and convenience for long-term travelers compared to daily alternatives
• Established long-term safety profile for durations up to one year of continuous use when tolerated
• Does not require refrigeration, making it suitable for travel to remote areas with limited infrastructure
• Coverage continues for several weeks after discontinuation due to extended half-life
• Well-studied in various populations including military personnel and long-term expatriates

Common use

Lariam is primarily prescribed for malaria prophylaxis in non-immune individuals traveling to areas with chloroquine-resistant malaria transmission, particularly sub-Saharan Africa, Southeast Asia, and the Amazon Basin. It is also used off-label for the treatment of acute uncomplicated malaria when other first-line agents are unavailable or contraindicated. The medication is typically initiated 2-3 weeks before travel to assess tolerance, continued weekly during exposure, and maintained for 4 weeks after leaving the endemic area to cover the parasite’s incubation period.

Dosage and direction

For malaria prophylaxis in adults: 250 mg (one tablet) orally once weekly. Begin 1-2 weeks before travel to assess tolerance, continue weekly during exposure, and maintain for 4 weeks after leaving endemic area.

Pediatric dosing (based on body weight):

• ≤9 kg: 5 mg/kg base (approximately ¼ tablet)
• 10-19 kg: ¼ tablet
• 20-30 kg: ½ tablet
• 31-45 kg: ¾ tablet

• 45 kg: 1 tablet

Administer with food and at least 8 oz of water to minimize gastrointestinal upset. The weekly dose should be taken on the same day each week. If vomiting occurs within 30 minutes of administration, a repeat dose should be taken.

Precautions

Lariam requires careful patient selection and monitoring due to its potential for neuropsychiatric adverse effects. A thorough medical history should assess for pre-existing psychiatric conditions, seizure disorders, or cardiac conduction abnormalities. Baseline ECG is recommended for patients with cardiac history. Patients should be counseled to report immediately any symptoms of depression, anxiety, hallucinations, confusion, or unusual behavior. The medication should be discontinued at the first sign of neurological or psychiatric symptoms. Use with caution in patients with hepatic impairment due to extensive liver metabolism. Periodic liver function tests are advisable during prolonged therapy.

Contraindications

Lariam is contraindicated in patients with known hypersensitivity to mefloquine or related compounds (quinine, quinidine). Absolute contraindications include: history of epilepsy or seizure disorders; active or recent history of depression, generalized anxiety disorder, psychosis, or other major psychiatric disorders; history of blackwater fever; and concomitant use with drugs that prolong QT interval (certain antiarrhythmics, antipsychotics, antidepressants, antibiotics). It is contraindicated in persons with cardiac conduction abnormalities or arrhythmias.

Possible side effects

Common side effects (≥1%):

• Dizziness, vertigo, loss of balance
• Gastrointestinal disturbances (nausea, vomiting, diarrhea)
• Headache, sleep disorders (insomnia, vivid dreams)
• Visual disturbances

Serious side effects requiring immediate medical attention:

• Neuropsychiatric reactions: depression, anxiety, paranoia, hallucinations, suicidal ideation
• Seizures, convulsions
• Cardiac arrhythmias, palpitations
• Severe skin reactions
• Hepatitis, elevated liver enzymes

Post-marketing surveillance has identified rare cases of persistent dizziness and vestibular damage that may continue for months or years after discontinuation.

Drug interaction

Lariam has significant interactions with multiple drug classes:

• QT-prolonging agents: Increased risk of torsades de pointes (antiarrhythmics, macrolides, antipsychotics)
• Anticonvulsants: May reduce seizure threshold and antagonize anticonvulsant effects
• Beta-blockers: Potential for bradycardia and cardiac conduction defects
• Chloroquine: Increased risk of convulsions
• Typhoid vaccine: May reduce antibody response (administer at least 3 days apart)
• Ketoconazole: May increase mefloquine concentrations
• Anticoagulants: Possible potentiation of warfarin effect

Missed dose

If a weekly dose is missed, the patient should take it as soon as remembered, then resume the regular weekly schedule. However, if the next dose is due within 2-3 days, skip the missed dose and continue with the regular schedule. Patients should never double the dose to make up for a missed one. If two consecutive doses are missed, medical consultation is recommended regarding continued prophylaxis.

Overdose

Mefloquine overdose may be fatal and presents with exaggerated adverse effects including severe nausea, vomiting, convulsions, cardiac arrhythmias, and neuropsychiatric symptoms. There is no specific antidote. Management is supportive and symptomatic: gastric lavage if presented early, activated charcoal, cardiac monitoring, and control of seizures with benzodiazepines. ECG monitoring should continue for at least 24 hours due to the drug’s long half-life. Dialysis is not effective due to high protein binding.

Storage

Store at controlled room temperature (15-30°C or 59-86°F) in the original container. Protect from light and moisture. Keep out of reach of children. Do not use after the expiration date printed on the packaging. Tablets should not be removed from blister packaging until immediately before administration.

Disclaimer

This information is for educational purposes only and does not constitute medical advice. Lariam is a prescription medication that requires careful medical supervision. The prescribing physician must evaluate individual risk factors and make treatment decisions based on the latest clinical guidelines. Patients should disclose their complete medical history and current medications to their healthcare provider. Malaria prophylaxis should be part of a comprehensive prevention strategy that includes mosquito avoidance measures.

Reviews

Clinical studies demonstrate Lariam’s efficacy in malaria prophylaxis ranges from 85-95% when taken correctly. However, patient satisfaction varies significantly due to side effect profile. Many travel medicine specialists reserve Lariam for specific circumstances where benefits outweigh risks, particularly for travel to areas with high prevalence of multidrug-resistant malaria. The medication continues to be valuable for certain populations despite the availability of alternative agents, particularly for long-term travelers to highly endemic regions.