The Pharmaceutical Journal
Vol 269 No 7214 p309
7 September 2002

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Drug Safety Research Unit (www.dsru.org)

Incidence of GI events differs among COX-2s

Patients treated with the cyclo-oxygenase-2 inhibitor rofecoxib (Vioxx) are less likely to experience gastrointestinal (GI) symptoms than those treated with the partially selective COX-2 inhibitor meloxicam (Mobic), new data indicate.

Dr Saad Shakir and colleagues from the Drug Safety Research Unit in Southampton conducted an observational study using the unit's prescription event monitoring database. They found that of 19,089 patients treated with meloxicam, 1,392 (7.3 per cent) were recorded as having symptomatic, non-serious acid/peptic symptoms. This compared with 1,169 (7.6 per cent) of the 15,266 patients treated with rofecoxib. "We certainly saw a significant reduction in non-serious gastrointestinal events," Dr Shakir told The Journal.

After adjusting for confounding factors, the researchers calculated that the relative risk for non-serious GI events for rofecoxib compared with meloxicam was 0.69 (95 per cent confidence interval 0.63–0.76). No significant difference was found in the rates of complicated upper GI events between the two groups.

The researchers suggest that one explanation for the different incidence of non-serious upper GI events could be that meloxicam exhibits dose-dependent COX-2 inhibition and some COX-1 inhibition at therapeutic doses. "However, the incidence rates in this study reflect the entire starting dose range used and cannot provide evidence for a dose-response relationship," they add.

Dr Shakir pointed out that both drugs were marketed with assertions of improved GI tolerability over non-selective non-steroidal anti-inflammatory drugs and that "channelling" of both treatments to high-risk groups is likely.

The research unit is supported by grants from the pharmaceutical industry, including grants from Merck Sharp & Dohme, manufacturer of Vioxx.

A spokeswoman for Boehringer Ingelheim, manufacturer of Mobic, pointed out that treatment duration was different for the two observational groups. "Meloxicam patients were studied for a longer treatment time, which will lead to some more events. If the study was adjusted for this discrepancy accordingly, the reported incidences of symptomatic acid/peptic upper GI events in patients prescribed rofecoxib compared with meloxicam are similar," she said.