The evolution of human immunodeficiency virus in America ranges from the 1990 death of teenager Ryan White to the continuing legacy of basketball star "Magic" Johnson, beneficiary of modern antiretroviral therapy.

Whereas White died early after developing AIDS, Johnson and others have in the ensuing years benefited from the tremendous success of drugs suppressing replication of HIV in the body. Within two years, half the population with HIV in the United States would be older than 50, federal health officials say.

However, some people have been using the antiretroviral Efavirenz for a recreational high, given the drug's psychoactive properties — a practice that could encourage drug-resistant strains of HIV, said John A. Schetz, a neuropharmacologist at the University of North Texas Health Science Center in Fort Worth, Texas.

Schetz said anecdotal reports from South Africa describe users crushing the pills into a powder to smoke for its psychoactive effects. Though no studies on recreational use of the drug have been conducted, the researcher said studies have shown neuropsychiatric side effects in patients taking the drug as prescribed, in addition to sudden adverse psychiatric episodes in patients with no history of mental illness.

One qualification, however: A study suggests the latter psychiatric episodes, as opposed to milder experiences of side effects, occurred only in patients with a genetic variant of the enzyme used to metabolize the drug — causing higher levels of the drug to linger in the body. The highly efficacious drug, in standard dosage, carries the risk of a host of side effects including depression, anxiety, sleep disturbances and night terrors, impaired concentration, aggression, hallucinations, paranoia, psychosis, and delusions.

Speaking at the Experimental Biology 2013 in Boston, Schetz said he investigated the molecular profiling of the receptor pharmacology of the drug, which led to identification of interactions with multiple sites of action for other known drugs of abuse. He and his colleagues achieved a "pre-clinical" understanding of the drug's psychoactivity, which may help to explain the side effects and recreational use.

The psychopharmacology work might now draw interest from other researchers to study the mechanisms of HIV medications in an effort to learn more about side effects and the potential for abuse, while also improving quality of life for patients.

More than 1 in 270 Americans lives with HIV with a new infection occurring every 9.5 minutes, experts say. Aside from the human cost, the U.S. economy loses at least $36 billion per year from HIV and AIDS.