Antimalarial Pregnancy: Mefloquine was teratogenic in mice and rats and embryotoxic in rabbits, but large clinical experience with prophylactic use has not revealed an embryotoxic or teratogenic effect and limited data from exposed pregnancies indicate no adverse effects on pregnancy or the health of the foetus/newborn. Pregnant women or women wishing to become pregnant should be discouraged from travelling in endemic areas; prophylactic treatment may be considered regardless of the term of pregnancy but in strict respect of the indications. Curative use in pregnancy is limited to acute uncomplicated malaria when quinine is contraindicated or in P. falciparum resistance to quinine. Unplanned pregnancy during chemoprophylaxis is not an indication for termination. Breast-feeding: mefloquine is secreted into breast milk in small amounts of unknown activity and should be avoided as a precautionary measure. Consult current national and international guidelines.

Mefloquine

Brand names: Lariam

Mefloquine is an antimalarial agent used for the prophylaxis and treatment of malaria, including in areas with chloroquine-resistant Plasmodium falciparum.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Malaria chemoprophylaxis: 250 mg (one tablet) once weekly for adults and children of more than 45 kg bodyweight — the recommended chemoprophylactic dose is approximately 5 mg/kg bodyweight once weekly. Curative treatment: total therapeutic dose 20 to 25 mg/kg — 4 to 5 tablets (>45 to 60 kg) or 6 tablets (>60 kg)

Route: Oral — tablets should be swallowed whole, preferably after a meal, with plenty of liquid

Frequency: Prophylaxis: once weekly, always on the same day. Start 10 days before departure (first intake 10 days before, second intake 3 days before departure), then once a week on a fixed day; continue for 4 weeks after leaving a malarious area (minimum treatment period 6 weeks). Curative treatment: the total therapeutic dose may be split into 2-3 doses (e.g. 3+1, 3+2 or 3+2+1 tablets) taken 6-8 hours apart to limit adverse reactions

Max: Chemoprophylaxis: the maximum recommended duration of administration is 12 months. Curative treatment: there is no specific experience with total dosages of more than 6 tablets in very heavy patients

Tablet strength 250 mg (source product: Lariam 250 mg tablets). CHEMOPROPHYLAXIS DOSE BY WEIGHT (SPC table): adults and children over 45 kg — 1 tablet; 31-45 kg — three-quarters of a tablet; 20-30 kg — half a tablet; 5-19 kg — a quarter of a tablet; all once weekly. CURATIVE TREATMENT TOTAL DOSE BY WEIGHT (SPC table): under 20 kg — a quarter tablet per 2.5-3 kg, or 1 tablet per 10-12 kg (experience in infants under 3 months old or weighing less than 5 kg is limited); 20-30 kg — 2-3 tablets; over 30 to 45 kg — 3-4 tablets; over 45 to 60 kg — 4-5 tablets; over 60 kg — 6 tablets. A second full dose should be given to patients who vomit less than 30 minutes after receiving the drug; if vomiting occurs 30-60 minutes after a dose, an additional half-dose should be given. If a full treatment course does not lead to improvement within 48-72 hours, alternative treatments should be considered. Mefloquine can be given for severe acute malaria after an initial course of intravenous quinine lasting at least 2-3 days, allowing an interval of at least 12 hours after the last quinine dose. Artemisinin combination therapy (ACT) is recommended as the standard of care for P. falciparum malaria and mefloquine is a recommended partner molecule for inclusion in ACT. ELDERLY: no specific adaptation of the usual adult dosage is required. When chemoprophylaxis with mefloquine fails, physicians should carefully evaluate which antimalarial to use for therapy. US labelling cross-check: treatment of mild to moderate malaria in adults — five tablets (1250 mg) as a single oral dose; prophylaxis — one 250 mg tablet once weekly beginning 1 week before arrival in an endemic area and continued for 4 weeks after leaving.

Paediatric dose

Dose: 5 mg/kg

Route: Oral — swallowed whole, preferably after a meal, with plenty of liquid

Frequency: Once weekly (chemoprophylaxis), always on the same day

Max: 1 tablet (250 mg) once weekly — the dose for children and adults of more than 45 kg bodyweight

SPC §4.2 verbatim: 'The recommended chemoprophylactic dose of mefloquine is approximately 5 mg/kg bodyweight once weekly.' Weight-band table for children and adults weighing less than 45 kg: 5-19 kg — a quarter tablet; 20-30 kg — half a tablet; 31-45 kg — three-quarters of a tablet; once weekly. CURATIVE TREATMENT (separate regimen): recommended total therapeutic dose 20 to 25 mg/kg — under 20 kg a quarter tablet per 2.5-3 kg or 1 tablet per 10-12 kg; 20-30 kg 2-3 tablets; over 30 to 45 kg 3-4 tablets; the total dose may be split into 2-3 doses 6-8 hours apart. Experience with mefloquine in infants less than 3 months old or weighing less than 5 kg is limited. US labelling adds that the paediatric dose should not exceed the adult dose, that experience below 20 kg is limited, and that safety and effectiveness for treatment below 6 months of age have not been established. Verify against a children's formulary before use.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Paediatric weight-based calculator

Patient weight (kg)

Verify in a children's formulary

Contraindications

Known hypersensitivity to mefloquine or related compounds (e.g. quinine, quinidine) or to any excipient
Chemoprophylaxis in patients with active depression, a history of depression, generalised anxiety disorder, psychosis, suicide attempts, suicidal ideation and self-endangering behaviour, schizophrenia or other psychiatric disorders, or with a history of convulsions of any origin
Concomitant halofantrine — must not be used during mefloquine chemoprophylaxis or treatment, or within 15 weeks after the last dose of mefloquine (risk of potentially fatal QTc prolongation)
History of Blackwater fever
Severe hepatic impairment (prophylactic use in patients with severe impairment of liver function should be regarded for the time being as a contraindication)

Side effects

Psychiatric — abnormal dreams and insomnia (very common); depression and anxiety (common); suicide, attempted suicide, suicidal ideation and self-endangering behaviour, psychotic disorder, paranoia, panic attacks, confusional state, hallucinations, aggression, agitation, mood swings (not known)
Nervous system — dizziness and headache (common); encephalopathy, convulsions, amnesia (sometimes lasting more than 3 months), syncope, memory impairment, balance and gait disturbance, peripheral neuropathy, somnolence (not known)
Gastrointestinal — nausea and vomiting are among the most common reactions to chemoprophylaxis; decreased appetite
Eye and ear — visual impairment and vertigo (common); cataract, retinal disorders and optic neuropathy, tinnitus, partial deafness, vestibular disorders (not known)
Blood and immune — agranulocytosis, aplastic anaemia, leukopenia, leukocytosis, thrombocytopenia; hypersensitivity ranging from mild cutaneous events to anaphylaxis (not known)

Interactions

Halofantrine — must not be used during or within 15 weeks after mefloquine; risk of potentially fatal QTc prolongation
Ketoconazole — increased mefloquine plasma concentrations and elimination half-life; risk of QTc prolongation if taken during or within 15 weeks after mefloquine
Other related antimalarials (quinine, quinidine, chloroquine) — may produce electrocardiographic abnormalities and increase the risk of convulsions; if used in the initial treatment of severe malaria, allow an interval of at least 12 hours after the last quinine dose before mefloquine
Anticonvulsants — concomitant administration in patients with epilepsy; mefloquine may increase the risk of convulsions and should be used only for curative treatment in such patients
Beta-blockers — one report of cardiopulmonary arrest, with full recovery, in a patient taking propranolol (US labelling)

Clinical monograph

How it works

It is a blood schizonticide active against the erythrocytic stages of malaria parasites; its precise mechanism is not fully defined but is thought to involve interference with the parasite's haem detoxification within the food vacuole.

Prescribing in practice

Neuropsychiatric adverse effects, including abnormal dreams, anxiety, depression and rarely psychosis, are recognised, and it is contraindicated in those with a history of certain psychiatric conditions or seizures, with MHRA advice highlighting these risks.
When used for prophylaxis it should be started before travel so tolerability can be assessed and continued for the recommended period after leaving the malarious area.
It can affect cardiac conduction and should be used cautiously with other agents that influence the QT interval or in relevant cardiac conditions.

Monitoring

Review for neuropsychiatric symptoms during prophylaxis and treatment, and reassess if such effects emerge.

Counselling the patient

Stop the medicine and seek advice if you develop anxiety, depression, restlessness or confusion.
Begin prophylaxis before you travel and continue it for the full period after you return.
Take it with food and water on the same day each week as directed for prevention.

Evidence & guidelines

MHRA guidance details the neuropsychiatric risk profile of mefloquine and the importance of contraindications and patient counselling.

Reference: MHRA Drug Safety Update; UK malaria guidelines; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Pathways