Patients taking the antipsychotic drugs olanzapine (sold under the brand name Zyprexa by Eli Lilly and Co.) and clozapine (sold as Clorazil by Novartis AG) have been known to gain so much weight that they are placed at increased risk for obesity-related disorders such as diabetes and cardiovascular disease.
"Their use has been hampered primarily by the fact that for some of them there is this horrible gain, largely due to just eating too much from increased appetite," said Dr. Solomon Snyder, a professor of neuroscience at Johns Hopkins School of Medicine, where the study was based.
"It's a big increase and it occurs with very little doses of the drug," he said.
The results of the study, which involved experimentation on mice, suggest that the antipsychotics interfere with the protein histamine, leading to an increase in AMPK activity. Histamine is an important actor in local immune responses -- including allergy symptoms -- that has long been suspected to play a role in controlling weight.
Snyder expressed hope that the new study's findings could aid in the development of antipsychotic drugs to do not lead to weight gain.
"Unfortunately, Zyprexa, which everybody agrees is the best therapeutic agent, gives the worst weight gain, along with clozapine, the parent drug in the class," he said.
But consumer advocate Mike Adams, Mike Adams, author of "How to Halt Diabetes in 25 Days," instead took the results as a sign of the inherent risks of psychiatric drugs.
"We've known for a long time that antipsychotic drugs cause severe blood sugar imbalances and even increase the risk of diabetes," Adams said
"Now scientists are pinpointing the biochemical mechanism by which these drugs cause massive weight gain, an average of 22 pounds in the first year. That's enough to make anyone depressed -- which, of course, often leads to stronger, more dangerous drugs being prescribed. As a result, antipsychotic drugs actually create their own repeat revenue by keeping patients depressed and overweight."