Marines with Ground Combat Element, Security Cooperation Task Force Africa Partnership Station 2011 take doxycycline in accordance with a weekly dosage of mefloquine to prevent the spread of malaria.

LOS ANGELES — Federal drug officials have issued a strong new warning about a controversial anti-malaria medication once routinely given to U.S. troops, some of whom say it damaged them permanently.

The Food and Drug Administration ordered manufacturers of mefloquine hydrochloride to give the medicine a black box label, the agency's strongest warning, reserved for drugs with significant risks of serious side effects. The FDA said that some neurological and psychiatric side effects can last for months or years after a patient stops taking the drug.

The medication was approved by the FDA in 1989 under the brand name Larium and quickly became a leading drug for preventing and treating malaria — among travelers and the military.

While other drugs must be taken daily, one tablet a week of mefloquine offers protection against the sometimes-deadly mosquito-borne parasite, including against strains that are resistant to other medications.

But the drug has long carried warnings tying it to dizziness, seizures, insomnia, anxiety, depression and strange dreams. One clinical trial found that 29% of travelers who took mefloquine experienced at least one of those side effects. There is also evidence suggesting a link to violent behavior, including suicide.

Amid growing concerns, the drug fell out of favor over the last decade. Roche, its original manufacturer, stopped selling Larium in the U.S. in 2008. The generic versions still on the market accounted for 226,000 of the 5.4 million U.S. prescriptions for anti-malaria drugs last year, according to IMS Health, which tracks drug trends.

The Pentagon, which used the drug widely in Somalia and during the early years of the wars in Iraq and Afghanistan, offered little explanation when it began scaling back its reliance on mefloquine and eventually recommended that the drug be used only as a third choice. Military officials continued to dismiss the claims of veterans who insisted that the side effects could be long-lasting.

The new FDA warning provided those veterans a sense of validation.

"I almost fell out of my chair when [the news] was forwarded to me," said Greg Alderete, a retired Army lieutenant colonel who blames his chronic balance and memory problems on the drug, which he took while serving in Somalia in 1993.

Alderete said that in 2008 he started to suspect mefloquine after connecting with other veterans of Somalia who were experiencing similar symptoms.

He eventually helped launch a Facebook group, Veterans Against Larium, which now has more than 1,100 members. He said most served in Somalia, but the group has also attracted veterans from other wars.

Alderete acknowledged that his depression, anger and anxiety could be the result of post-traumatic stress disorder, with which he was diagnosed. But his chronic dizziness and nausea and an inability to remember words are less easily explained.

"There was a big gray zone," he said. "I'm not sure where mefloquine begins and PTSD ends."

Doctors from the U.S. Department of Veterans Affairs have insisted that his problems are not related to the drug, he said.

The FDA strengthened its warning this week based on a new review of medical literature and reports of patients suffering from dizziness, loss of balance, tinnitus and vertigo, according to a statement from the agency.

The symptoms often started after the first dose or two but continued for months or years. In some cases, the damage was deemed permanent. Usually, the neurological symptoms were accompanied by psychiatric ones, including anxiety, confusion, paranoia and depression, which were also long-lasting.

Dr. Remington Nevin, an epidemiologist who served in the Army and has been a leading critic of the drug, estimated that hundreds of thousands of U.S. troops have taken it.

"Now the military needs to take responsibility to clean up the toxic mess it's created," he said.

The controversy surrounding mefloquine has led to speculation by veterans and others that it may have played a role in the March 11, 2012, killing of 16 Afghan civilians by Army Staff Sgt. Robert Bales.

His lawyer, John Henry Browne, said the new FDA warning of long-term side effects could play a role in sentencing proceedings, which are scheduled to begin Aug. 19.

Bales had taken mefloquine while serving in Iraq, but it remains unclear whether he was taking the drug in Afghanistan, Browne said.

He said he is requesting the reports that served as the basis of the FDA warning.

alan.zarembo@latimes.com

