The drug, approved in almost 90 countries around the world and used by some seven million Americans, is particularly sought after at New Year's when many smokers typically make resolutions to end their nicotine addiction.
A federal judge in the southern US state of Alabama is reviewing the raft of lawsuits against Pfizer from former patients and relatives of those who used to take Chantix.
Lead attorney Ernest Cory accused Pfizer of negligence in bringing the drug to the US market in 2006, citing complaints from users of "neuropsychological problems" including "suicide, attempted suicide, seizure and blackouts."
Over 100 suicides
Cory said that well over 100 Chantix users had actually committed suicide and estimated that 1,000 more cases would be filed against Pfizer.
"In 60% of the lawsuits that are filed now by individuals or their estate either an attempted suicide or a completed suicide occurs," he said.
Victoria Davis, a spokeswoman from the pharmaceutical giant, rejected any claims of wrongdoing.
"Pfizer acted responsibly and appropriately at all times in connection with the development, approval, and marketing of Chantix," she said.
"There is no reliable scientific evidence that Chantix causes the neuropsychiatric events alleged in these lawsuits. Chantix is an effective treatment option for many smokers who want to quit, and we intend to defend this important medication."
Cory suggested it was unlikely that judge Inge Johnson, who is reviewing the centralised cases, would decide that there could be one single trial covering all the suits.
If Chantix is found to be dangerous it could be withdrawn from the US market, where sales have suffered since alleged links to depression and suicide mushroomed last year.
(Sapa, January 2011)