07/14/2008- Pfizer's smoking-cessation drug Chantix could be the latest drug to land in the crosshairs of U.S. plaintiffs' attorneys, two new lawsuits suggest.

The medication induced manic, violent psychosis requiring his hospitalization in August 2007, a man claims in the lawsuit filed in U.S. District Court for the Eastern District of Pennsylvania.

Plaintiff Brian Kline claims New York City-based Pfizer "negligently concealed, oppressed or omitted" warnings about side effects, which have "caused serious injury and death."

The drug, known by the generic name varenicline, received an "accelerated" review by the U.S. Food and Drug Administration, the lawsuit says.

In a statement, Pfizer said it has acted "responsibly, appropriately and in the best interests of patient safety" in researching and marketing Chantix.

A second lawsuit filed in Indianapolis claims that Chantix led David Collins of Gas City, Ind., to commit suicide in January after using the medication as prescribed.

Linda Collins, the victim's widow, filed the suit Tuesday in U.S. District Court in Indianapolis.

The lawsuit claims that Pfizer failed to warn patients about the potential dangers if the drug, which acts by targeting the same drug receptors that nicotine does.

The Indiana lawsuit alleges that Pfizer purposely excluded people with a history of mental illness when it tested Chantix during clinical trials.

The lawsuit also alleges the active ingredient in Chantix was derived from cytosine, which has long been linked to suicide.

"I run a clinic, and two out of three (smokers) I see have psychiatric or mood problems," Dr. Daniel Seidman, director of Smoking Cessation Services at Columbia University Medical Center, was quoted as saying in the lawsuit.