CHICAGO — ON Oct. 16, 2002, at 4 p.m., I walked out of my apartment in Secunderabad, India, leaving the door wide open, the lights on and my laptop humming. I don’t remember doing this. I know I did it because the building’s night watchman saw me leave. I woke up the next day in a train station four miles away, with no idea who I was or why I was in India. A policeman found me, and I ended up strapped down, hallucinating in a mental hospital for three days.

The cause of this incident was drugs. And these drugs had been recommended to me by the Centers for Disease Control and Prevention.

I had been prescribed mefloquine hydrochloride, brand name Lariam, to protect myself from malaria while I was in India on a Fulbright fellowship.

Since Lariam was approved in 1989, it has been clear that a small number of people who take it develop psychiatric symptoms like amnesia, hallucinations, aggression and paranoia, or neurological problems like the loss of balance, dizziness or ringing in the ears. F. Hoffmann LaRoche, the pharmaceutical company that marketed the drug, said only about 1 in 10,000 people were estimated to experience the worst side effects. But in 2001, a randomized double-blind study done in the Netherlands was published, showing that 67 percent of people who took the drug experienced one or more adverse effects, and 6 percent had side effects so severe they required medical attention.