Neurologic and psychiatric
In 2013, the U.S. Food and Drug Administration (FDA) added a boxed warning to the prescription label of mefloquine regarding the potential for neuropsychiatric side effects that may persist even after discontinuing administration of the medication. In 2013 the FDA stated "Neurologic side effects can occur at any time during drug use, and can last for months to years after the drug is stopped or can be permanent." Neurologic effects include dizziness, loss of balance, seizures, and tinnitus. Psychiatric effects include nightmares, visual hallucinations, auditory hallucinations, anxiety, depression, unusual behavior, and suicidal ideations. Central nervous system events requiring hospitalization occur in about one in 10,000 people taking mefloquine for malaria prevention, with milder events (e.g., dizziness, headache, insomnia, and vivid dreams) in up to 25%. When some measure of subjective severity is applied to the rating of adverse events, about 11–17% of travelers are incapacitated to some degree. Cardiac
Mefloquine may cause abnormalities with heart rhythms that are visible on electrocardiograms. Combining mefloquine with other drugs that cause similar effects, such as quinine or quinidine, can increase these effects. Combining mefloquine with halofantrine can cause significant increases in QTc intervals. : 10

Contraindications
Mefloquine is contraindicated in those with a previous history of seizures or a recent history of psychiatric disorders. Pregnancy and breastfeeding
Available data suggests that mefloquine is safe and effective for use by pregnant women during all trimesters of pregnancy, and it is widely used for this indication.
Plasma concentrations of the (–)-enantiomer are significantly higher than those for the (+)-enantiomer, and the pharmacokinetics between the two enantiomers are significantly different. The (+)-enantiomer has a shorter half-life than the (–)-enantiomer. History
Mefloquine was formulated at Walter Reed Army Institute of Research (WRAIR) in the 1970s shortly after the end of the Vietnam war. Mefloquine was number 142,490 of a total of 250,000 antimalarial compounds screened during the study.Mefloquine was the first Public-Private Venture (PPV) between the US Department of Defense and a pharmaceutical company. WRAIR transferred all its phase I and phase II clinical trial data to Hoffman-LaRoche and Smith Kline. FDA approval as a treatment for malaria was swift. Most notably, phase III safety and tolerability trials were skipped.The drug was first approved in Switzerland in 1984 by Hoffmann-LaRoche, who brought it to market with the name Lariam.However, mefloquine was not approved by the FDA for prophylactic use until 1989. This approval was based primarily on compliance, while safety and tolerability were overlooked.