BACKGROUND AND OBJECTIVE: Non-steroidal anti-inflammatory drugs (NSAIDs) frequently cause pseudoallergic reactions. Recognition of two different prostaglandin synthase iso-enzymes led to the development of the so-called coxibs preferentially inhibiting cyclooxygenase-2. We studied tolerability of valdecoxib preferentially inhibitng cyclooxygenase-2 in patients with a history of intolerance to NSAIDs. PATIENTS AND METHODS: 41 patients (30 female, 11male, age 14-74 years) with a history of intolerance to NSAIDs underwent scratch tests with these drugs and valdecoxib, followed by oral challenge with valdecoxib (maximum single dose: 20 mg; cumulative dose: 35mg) in a double-blind, placebo-controlled manner. RESULTS: The history of intolerance to NSAID comprised urticaria as the leading symptom (n = 26), followed by angioedema (n = 11) and anaphylactoid shock (n = 4). 21 patients reported reactions to only one NSAID, 15 identified 2 different triggering drugs, and 5 patients showed reactions to 3 different NSAIDs. Acetylsalicylic acid (n = 20) and diclofenac (n = 12) were the most frequent causative drugs. Upon oral challenge with valdecoxib, one patient developed generalized urticaria within 30 minutes following the last dose of valdecoxib; symptoms resolved after i. v. injection of 2 mg clemastine and 250 mg prednisolone. All other patients tolerated the oral challenge without adverse effects. CONCLUSION: Our results are in line with previous studies suggesting that preferential cyclooxygenase-2-inhibitors may safely be used by patients with known intolerance to NSAIDs.