New Zealand scientists said Wednesday that Pfizer’s painkiller Celebrex is no safer than other drugs like Vioxx in the COX-2 inhibitor class that have been pulled from the market, adding to questions about the drug’s future.

Unlike other COX-2 inhibitors, like Pfizer’s Bextra and Merck’s Vioxx, Celebrex remains on the market with the U.S. Food and Drug Administration’s strongest possible safety warning label.

The new study is published in the March issue of the Journal of the Royal Society of Medicine. It is a type of mathematical review called a meta-analysis that brings together data from lots of different studies, often with conflicting conclusions, to provide an overall answer to a scientific problem.

In the case of Celebrex, a trial called CLASS (Celecoxib Long-term Arthritis Safety Study) has reported that the drug does not cause an increase in major cardiovascular problems, including heart attack. But another trial called the Colorectal Adenoma Prevention Trial reported a 2.3- and 3.4-fold increased risk of cardio problems in people who took daily doses of the drug of 400mg and 800 mg.

“This systematic review and meta-analyses provide evidence of an increased risk of myocardial infarction [heart attack] associated with the use of celecoxib [Celebrex’s scientific name], consistent with a class effect of COX-2 inhibitors,” said the paper. “This finding would suggest that the preferential risk/benefit assessment afforded celecoxib over other COX-2 inhibitors by the FDA may not be supported by the currently available evidence."

Pfizer did not respond to calls requesting immediate comment on the study. Wall Street ignored the finding, with Pfizer shares rising $0.07 to $26.26 on Wednesday.

The company has previously maintained that it disagrees with the FDA over the need for Bextra to be pulled from the market and Celebrex’ black box label, although it complied with the agency’s requests (see Pfizer Yanks Bextra off Market).

The new analysis’ findings could have legal importance because Pfizer has a date in an Alabama court next June. An American woman is suing the company because she believes Celebrex caused a stroke she suffered in 2005.

Merck is embroiled in several thousand similar trails related to its COX-2 inhibitor, Vioxx (see A Merck-y View of Vioxx Cases).

The new analysis by researchers at the Wellington School of Medicine and Health Sciences in Wellington, New Zealand, looked first at many studies comparing Celebrex’ cardio risks with those of placebo. It also looked at studies comparing its side-effects with those with a class of common painkillers also linked to heart attacks and strokes (see New Warning on Painkillers).

They found that Celebrex was associated with a 2.26-fold increased risk of heart attack when compared to placebo, and a 1.88-fold increase when compared with other painkillers.