Lariam (mefloquine hydrochloride) is a prescription antimalarial medication indicated for the prophylaxis of Plasmodium falciparum and Plasmodium vivax malaria in travelers. As a long-acting chemoprophylactic agent, it is particularly suited for extended travel to regions with known chloroquine-resistant malaria strains. Its once-weekly dosing regimen offers significant convenience, making adherence more manageable over prolonged periods in remote or high-risk areas. Healthcare providers must conduct a thorough risk-benefit assessment prior to prescription due to its specific neuropsychiatric profile and contraindications.

Features

• Active ingredient: Mefloquine hydrochloride (250 mg per tablet)
• Formulation: Oral tablet
• Dosing frequency: Once weekly
• Onset of prophylactic effect: 1–3 weeks prior to exposure
• Duration of protection: Continues for 4 weeks after last dose
• Manufacturer: Original developer and licensed under various generics
• FDA-approved since 1989 for malaria prophylaxis

Benefits

• Provides robust, long-lasting protection against chloroquine-resistant malaria strains.
• Weekly dosing enhances traveler compliance compared to daily alternatives.
• Effective in multiple high-risk geographical zones, including parts of Africa, Southeast Asia, and South America.
• Suitable for long-term travel or residency in endemic areas.
• Does not require daily routine disruption, supporting discreet and convenient prophylaxis.
• One of the few options effective for prophylaxis in regions with multidrug-resistant parasites.

Common use

Lariam is primarily prescribed for malaria prophylaxis in non-immune individuals traveling to or residing in areas with a high risk of malaria transmission, particularly where chloroquine resistance has been documented. It is also used off-label for the treatment of acute malaria infections under strict medical supervision. Typical user profiles include military personnel, aid workers, long-term travelers, and expatriates. It is not recommended for short-term travel or casual tourism where lower-risk alternatives may be appropriate.

Dosage and direction

For malaria prophylaxis in adults: one 250 mg tablet once per week. Begin dosing 1–3 weeks before entering the malarious area to establish therapeutic blood levels and assess tolerability. Continue weekly dosing during exposure and for 4 weeks after leaving the endemic area. Take with food and at least 8 oz of water to minimize gastrointestinal upset. If vomiting occurs within 30 minutes of ingestion, a repeat dose should be taken. For pediatric use, dosage is weight-based and must be carefully calculated by a physician.

Precautions

Prior to prescribing, screen patients for personal or family history of psychiatric disorders, seizures, or cardiac arrhythmias. Conduct a baseline neurological and psychiatric evaluation. Avoid use in individuals with active depression, generalized anxiety disorder, psychosis, or other major neuropsychiatric conditions. Use with caution in patients with hepatic impairment. Periodic clinical evaluations are recommended during prolonged use. Patients should be advised not to operate heavy machinery or engage in hazardous activities until their response to the drug is known.

Contraindications

Lariam is contraindicated in patients with known hypersensitivity to mefloquine or related compounds (e.g., quinine, quinidine). It must not be used in individuals with a history of epilepsy or convulsive disorders. Contraindicated in those with active or recent history of depression, anxiety disorders, psychosis, suicidality, or other severe psychiatric disturbances. Not recommended for use in patients with significant cardiac conduction disorders or severe hepatic impairment. Avoid concurrent use with drugs that may alter cardiac conduction.

Possible side effects

Common side effects include dizziness, headache, sleep disturbances (insomnia, vivid dreams), nausea, vomiting, diarrhea, and abdominal pain. Less frequently, patients may experience visual disturbances, tinnitus, rash, or hair loss. Serious side effects require immediate medical attention: seizures, severe dizziness, irregular heartbeat, mood changes (e.g., depression, anxiety, hallucinations), confusion, or signs of hypersensitivity reactions. Neuropsychiatric events may occur during use or after discontinuation.

Drug interaction

Lariam may interact with anticonvulsants (e.g., valproate, carbamazepine), potentially reducing seizure threshold. Concurrent use with other QT-prolonging agents (e.g., antiarrhythmics, certain antibiotics, antipsychotics) may increase risk of arrhythmias. Avoid concomitant administration with chloroquine or quinine due to increased risk of convulsions and cardiotoxicity. Caution is advised with drugs metabolized by CYP3A4. Live typhoid vaccine efficacy may be reduced; administer at least 3 days apart.

Missed dose

If a weekly dose is missed, instruct the patient to take it as soon as possible. If it is near the time for the next dose, skip the missed dose and resume the regular weekly schedule. Do not double the dose. Consistent weekly dosing is critical to maintain prophylactic blood levels. Patients should mark a calendar or set reminders to support adherence.

Overdose

Overdose may exaggerate known adverse effects, including severe nausea, vomiting, dizziness, syncope, and transient CNS stimulation followed by lethargy. Cardiac effects such as bradycardia or QT prolongation may occur. Management is supportive: gastric lavage if recent ingestion, with ECG monitoring and symptomatic treatment. There is no specific antidote. Maintain cardiac and respiratory function and provide appropriate psychiatric support if neuropsychiatric symptoms manifest.

Storage

Store at room temperature (15–30°C or 59–86°F) in a tightly closed container. Protect from light and moisture. Keep out of reach of children and pets. Do not use beyond the expiration date printed on packaging. Do not store in bathrooms or damp areas. Properly dispose of unused medication via drug take-back programs.

Disclaimer

This information is for educational purposes and does not replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before starting, changing, or stopping any medication. Individual response to Lariam may vary. The prescriber is responsible for evaluating patient-specific risks and benefits. Not all side effects or interactions are listed here. In case of emergency, contact poison control or seek immediate medical attention.

Reviews

Clinical studies and post-marketing surveillance indicate that Lariam is effective in preventing malaria in up to 90% of users when taken correctly. However, user experiences vary widely. Some travelers report excellent tolerance and convenience with the weekly regimen, especially during long deployments. Others describe significant neuropsychiatric side effects that limited usability. Medical consensus emphasizes careful patient selection, pre-travel testing where feasible, and ongoing monitoring. Many infectious disease specialists reserve Lariam for specific high-risk scenarios where alternatives are unsuitable.