Identification of sulfonamide-like adverse drug reactions to celecoxib in the World Health Organization database.

BACKGROUND: The selective COX-2 inhibitor celecoxib has a sulfonamide structure and is contraindicated for patients with known sulfa allergy. However, there is currently no standard available for the identification of sulfonamide-related adverse drug reactions (ADRs) and the occurrence of such ADRs with celecoxib has not been established. THE AIMS OF THIS STUDY WERE: (1) to identify the typical pattern of sulfonamide ADRs from literature and verify this pattern in the World Health Organization (WHO) ADR database; and (2) to examine whether these sulfonamide ADRs occur more frequently with celecoxib than with the non-sulfonamide, COX-2 inhibitor rofecoxib.
METHODS: A sulfonamide ADR pattern was derived from the most extensive textbook source of ADRs and applied to the WHO database for the three groups of sulfonamide drugs: short- and intermediate-acting sulfonamides, and sulfasalazine. ADRs reported three or more times for each of these groups were included in a 'sulfonamide template' comprising 19 ADRs relating to the skin, the blood, the liver, and anaphylaxis. This template was then applied to celecoxib and rofecoxib.
RESULTS: Overall, the relative reporting rate of a sulfonamide-type ADR with celecoxib was 80% higher than with rofecoxib, whether this was based on total number of reports (RR 1.8, 95% Cl 1.6-1.9) or restricted to reports that listed coxibs as the sole suspected drugs (RR 1.8, 95% Cl 1.6-1.9). There were numerically more ADRs for celecoxib than for rofecoxib in 15 of the 19 terms. Within the ADRs in the sulfonamide template, relative reporting rate of fatal reactions was 80% higher with celecoxib (RR 1.8, 95% Cl 0.9-4.0). Even though serious sulfonamide reactions are rare, their clinical impact on patient safety warrants close monitoring as more data becomes available. Physicians should be aware of possible sulfonamide allergy when prescribing celecoxib.