Almost four decades after inventing a potent anti-malarial drug, the U.S. Army has pushed it to the back of its medicine cabinet.

The dramatic about-face follows years of complaints and concerns that mefloquine caused psychiatric and physical side effects even as it was used around the globe as a front-line defense against the mosquito-borne disease that kills about 800,000 people a year.

“Mefloquine is a zombie drug. It’s dangerous, and it should have been killed off years ago,” said Dr. Remington Nevin, an epidemiologist and Army major who has published research that he said showed the drug can be potentially toxic to the brain. He believes the drop in prescriptions is a tacit acknowledgement of the drug’s serious problems.

Over the past three years, the Army slashed by almost 75 percent the amount of mefloquine it prescribes, even as it sent thousands more soldiers to malaria-prone Afghanistan.

The decrease in doses followed orders from military and Pentagon leaders. In 2009, the Army’s surgeon general ordered the branch to limit its use to specific circumstances.