Answer: Mefloquine is an older generation anti-malarial drug that can produce vivid nightmares, anxiety, and hallucinations.
Mefloquine, also known by the brand name Lariam, is a drug that was developed in the 1960s by the United States Army. It is a prescription-only medication that is effective at decreasing the likelihood that a person contracts malaria when they are exposed to the disease. The drug is a strong prophylaxis against the Plasmodium falciparum protozoan parasite that causes malaria. It was adopted when several strains of malaria were found to be resistant to chloroquine, the previous antimalarial drug. The drug was given to many members of the military who were deployed to areas where malaria was a serious threat.
The dosage that was originally prescribed was originally one 250 mg tablet, once a week. This was preferable than many other antimalarial drugs, which required daily doses (Assessment of Long-Term Health Effects of Antimalarial Drugs When Used for Prophylaxis).
Side effects of mefloquine (Lariam)
Mefloquine or Lariam dosing is sometimes not well tolerated, as the side effects tend to include psychiatric disturbances. The best known side effects of the drug includes visual hallucinations and extremely vivid nightmares (Psychiatric Side Effects of Mefloquine: Applications to Forensic Psychiatry).
Mefloquine is also known to produce anxiety, panic attacks, paranoia, or depression-like symptoms including suicidal ideation. A cohort of patients taking mefloquine reported a higher number of incidents of violence against others, disproportionately higher than among the general public (Prescription Drugs Associated with Reports of Violence Towards Others). Some patients who experience these side effects report that even years after discontinuing use of the drug.
The mood dysregulation and visual hallucinations point to an effect of mefloquine on the serotonin signaling systems in the brain, but the exact mechanism is unknown. Many believe that electrical communication in limbic system brain structures is affected by mefloquine, which explains some of the symptoms including anterograde amnesia.
There is also a suggestion that mefloquine treatment leads to neurotoxicity. The cells of the limbic system may be the most vulnerable to long exposure to the drug (Limbic encephalopathy and central vestibulopathy caused by mefloquine: A case report).
On a molecular level, some evidence points to neuroinflammation, neurotransmitter dysregulation, and disruption of calcium homeostasis as potential mechanisms that may lead to neurotoxicity (Review of the mechanism underlying mefloquine-induced neurotoxicity)
Many of these side effects were so serious that mefloquine was deemed a “drug of last resort.”