The U.S. Food and Drug Administration (FDA) advisory panel ruled that the black box warning on Pfizer anti-smoking drug Chantix must remain. The recommendation stated that removing it might mislead consumers that Chantix no longer increases the risk of suicidal thoughts.

Chantix is manufactured by Pfizer. Doctors recommend using it along with behavior therapy and counselling to help people quit their smoking habits. The drug was associated with confusion, anxiety, hallucinations, depression and suicidal thoughts or self-inflicted pain. As a result, the FDA required Pfizer to include a warning label regarding these dangerous side effects in 2009.

Pfizer has since attempted to remove the black box warning and launched clinical trials to show the drug does not lead to suicidal thoughts. The company's study involved 8,000 smokers who underwent four treatments: Chantix, placebo, nicotine replacement therapies and Wellbutrin. In the early part of the study, none of the participants showed an increased risk of suicidal thoughts. The study results will be released in 2015.

"Currently available evidence do not support the existence of a causal relationship" between varenicline and serious neuropsychiatric events, Pfizer executive Dr. Christopher Wohlberg, told the committee, according to MedPage Today.

The FDA staff suggested the company finish the study first before asking it to approve the removal of the black box warning, according to the Wall Street Journal.

"We are not inclined to remove the boxed warning at this time because of the concern that such action could be interpreted as confirming 'no association' between [Chantix] use and neuropsychiatric risk, which is not supported by currently available observational data," the FDA wrote.

On Thursday, a majority of the FDA advisory panel followed the recommendation and voted in favor of keeping the black box warning to remind consumers of the side effects; only one panel member agreed with Pfizer.