Pfizer’s Chantix is once again in the center of attention but not in a good way, following the results of a study by the Veterans Administration, which involves about 33,000 veterans taking the anti-smoking drug.

All the veterans enrolling in the Chantix study were suffering from post traumatic stress disorder and had been recruited for a behavioral study with the drug, each of them being paid $30 a month.

The study was aimed at determining whether it is easier to stop smoking when smoking cessation treatment is combined with PTSD therapy, or whether the two therapies are more effective if they are provided separately, a statement posted on the VA’s Web site says.

According to the study’s results, of the 143 veterans with post traumatic stress disorder who took Chantix, 3 veterans or about 2 percent of the participants experienced thoughts of suicide. On the other hand, of the roughly 800 veterans in the study who did not take Chantix, 35 had suicidal thoughts or about 4.4 percent.

Following these results, the Veterans Affairs Department decided to send letters to all the participants in the study taking Chantix, warning them about possible side effects including thoughts of suicide, VA Secretary James Peake told reporters in a conference call Thursday, the Associated Press reported.

The letters also urged anyone experiencing side effects or worried about continuing to use the drug, to consult with their doctor. “Our first responsibility is to our veterans,” Peake said, according to ABC News. However, he added that they would not end the study although they would not hesitate to do it if needed. Some representatives in the Congress have already asked the cessation of this project.

“Chantix is an FDA-approved drug and we're trying to find the best way to support smoking cessation,” Peake said, adding there is no evidence suggesting the study should be ended.

Deputy White House Press Secretary Tony Fratto welcomed the VA’s decision saying the VA is doing whatever they can for the safety of their veterans.

No later than last month another report by the Institute for Safe Medication Practices, a non profit watchdog group, linked Chantix to 224 cases of potential heart-rhythm disturbances, 372 reports of possible movement disorders and 544 reports of likely glycemic problems, including diabetes. Also, there were 173 serious injuries, some resulting from traffic accidents where drivers on Chatix treatment were dizzy, mentally confused or became unconscious.

These findings prompted the Federal Aviation Administration and the Federal Motor Carrier Safety Administration to ban Chantix’ use by their pilots, air controllers and truckers.

Pfizer defended the drug at the time saying the label already contains safety warnings, which were added no further than February this year, when the FDA warned about the risk of mood and behavior changes for the second time. The warning also said Chantix could impair patient’s ability to drive or use heavy equipment.

“There are few things that provide greater health benefits than quitting smoking. When considering the use of Chantix for their patients, health care providers should discuss the risks of smoking, the health benefits of quitting smoking, and the product’s efficacy and safety profile,” a statement released by Pfizer’s representative Francisco Gebauer read at the time.