The antimalarial compound mefloquine (also known by its former brand name) Lariam is a mainstay of malaria prophylaxis. First developed in the 1970's by the US Military, to whom malaria has historically inflicted a countless amount of suffering, it has risen to such wide use that it is one of the drugs included on the WHO's Essential Medication List.
The advantage of mefloquine, in an era of malaria-drug resistance, was that it could be used as a preventative prophylactic in many malarious regions of the world (with parts of, for example Vietnam and Laos excepted).
All medications have side effects, however one of mefloquine's is becoming so notorious that it was used as a plot device on ABC's Revenge (Lariam is not a character's name, though it would be a good one). The side effect in questions are neuropsychiatric in nature and include hallucinations and bizarre behavior. Milder side effects such as vivid dreams occur in 25% of those taking the medication. In the show mefloquine was employed as a surreptitious means of causing a character to appear mentally ill.
These side effects are very real and have even had ramifications in the military's trial of Staff Sergeant Robert Barnes, convicted of killing 17 unarmed Afghanis. Barnes had no rationale to offer for his behavior and he had been on mefloquine in the past.
While I believe it not likely that a medication can induce someone to commit such an act. Psychiatric disturbances induced by the drug, in the presence of severe underlying neurologic or psychiatric disorders, may exacerbate homicidal or paranoid thoughts to extreme levels.
In today's legal environment, it will not be surprising when mefloquine use is cited as a mitigating factor in a legal proceeding. Fortunately, there are, in most cases, alternatives that can be used and the military has moved away from using mefloquine as its first line antimalarial. Additionally, more general usage has fallen off steeply since the FDA issued a black box warning regarding these side effects, which in some cases are permanent.
But, the importance of antimalarial prophylaxis can not be understated. Malaria is a killer and in 2011 the US reached a 40 year high of malaria importations when nearly 2,000 cases were reported. In 2012, approximately 1600 imported cases occurred with 6 deaths; ominously only 6% (!!) of individuals reported adherence to a recommended anti-malarial regimen.
Though mefloquine has serious side effects, the role of other anti-malarials is very important and non-compliance is a sure way to contract this dread disease.