In the mefloquine arm, 5% of the users reported severe events requiring medical attention, vs 1.2% in the atovaquone-proguanil arm.In August 2009, Roche stopped marketing Lariam in the United States.Retired soldier Johnny Mercer, who was later appointed Minister for Veterans Affairs by Boris Johnson, told in 2015 that he had received "a letter about once or twice a week" about ill-effects from the drug. In July 2016, Roche took this brand off the market in Ireland. Military
In 2006, the Australian military deemed mefloquine "a third-line drug" alternative, and over the five years from 2011 only 25 soldiers had been prescribed the drug, and only in cases of their intolerance for other alternatives. Between 2001 and 2012, 16,000 Canadian soldiers sent to Afghanistan were given the drug as a preventative measure. In 2013, the US Army banned mefloquine from use by its special forces such as the Green Berets. In autumn 2016, the UK military followed suit with their Australian peers after a parliamentary inquiry into the matter revealed that it can cause permanent side effects and brain damage.In early December 2016, the German defence ministry removed mefloquine from the list of medications it would provide to its soldiers.In autumn 2016, Canadian Surgeon General Brigadier General Hugh Colin MacKay told a parliamentary committee that faulty science supported the assertion that the drug has indelible noxious side effects. An expert from Health Canada named Barbara Raymond told the same committee that the evidence she had read failed to support the conclusion of indelible side effects.
It is typically taken for one to two weeks before entering an area with malaria. Doxycycline and atovaquone/proguanil provide protection within one to two days and may be better tolerated. If a person becomes ill with malaria despite prophylaxis with mefloquine, the use of halofantrine and quinine for treatment may be ineffective. : 4

Malaria treatment
Mefloquine is used as a treatment for chloroquine-sensitive or resistant Plasmodium falciparum malaria, and is deemed a reasonable alternative for uncomplicated chloroquine-resistant Plasmodium vivax malaria. It is one of several drugs recommended by the United States Centers for Disease Control and Prevention. It is not recommended for severe malaria infections, particularly infections from P. falciparum, which should be treated with intravenous antimalarials. Mefloquine does not eliminate parasites in the liver phase of the disease, and people with P. vivax malaria should be treated with a second drug that is effective for the liver phase, such as primaquine. : 4

Resistance to mefloquine
Resistance to mefloquine is common around the west border in Cambodia and other parts of Southeast Asia. The mechanism of resistance is by increase in Pfmdr1 copy number. Adverse effects
Common side effects include vomiting, diarrhea, headaches, and a rash. Severe side effects requiring hospitalization are rare, but include mental health problems such as depression, hallucinations, anxiety and neurological side effects such as poor balance, seizures, and ringing in the ears. Mefloquine is therefore not recommended in people with a history of psychiatric disorders or epilepsy.