Mefloquine is a chiral quinoline methanol.
Mefloquine is active against asexual forms of the four species of Plasmodium that infect humans.
It has some activity against the sexual forms (gametocytes) of P. vivax, malariae and ovale.
It is ineffective against gametocytes of P. falciparum and exoerythrocytic liver forms of Plasmodium species
Membrane-bound mefloquine may inhibit merozoite invasion and interact with proteins involved with parasite membrane lipid trafficking and nutrient uptake.
Mefloquine binds to haem, forming a complex that may also be toxic to the parasite.
Mefloquine-resistant field isolates of P. falciparum do have increased amounts of the pfmdr 1 gene and over-express the gene product suggesting that pgh-1 may be involved in mefloquine resistance.
Mefloquine is poorly water-soluble but relatively highly bio-available. The terminal elimination t½ is 14 to 28 days. Plasma protein binding is >98%.
While mefloquine is safe in pregnancy, there remain concerns over its use in the first trimester but this may be overstated.
Doses ranging from 125 to 250 mg every 1 to 2 weeks have shown a protective efficacy against both falciparum and vivax malaria (>95%).
For non-immune patients receiving mefloquine as sole treatment for falciparum malaria, the usual adult curative treatment dose is 15-25 mg/kg body weight and in children 15 to 30 mg/kg.
The most serious adverse effect of mefloquine treatment is neuropsychiatric toxicity and the symptoms can range from mild to life-threatening.
Serious reactions similar to those seen after treatment courses occur during prophylaxis at between 1 in 10,000 and 1 in 20,000 courses in large-scale studies.