Idiosyncrasy to Pyrazolone Drugs

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Abstract
Studies carried out in 68 patients with idiosyncratic reactions to noramidopyrine and/or aminophenazone led to distinction of 2 different groups. In the 1st group: noramidopyrine, aminophenazone, phenylbutazone, and sulfinpyrazone and several other inhibitors of cyclooxygenase, including aspirin, precipitated bronchoconstriction; skin tests with pyrazolone drugs were virtually negative; all patients had chronic asthma. In the 2nd group: noramidopyrine and aminophenazone induced anaphylactic shock and/or urticaria; skin tests with these drugs were highly positive; phenylbutazone, sulfinpyrazone and several other cyclooxygenase inhibitors, including aspirin, could be taken with impunity; chronic bronchial asthma was present in only 1/4 of the patients. Pathogenic mechanisms responsible for the idiosyncratic reactions probably involve inhibition of cyclooxygenase in the 1st group, and allergic reactions in the 2nd group. Distinction of these 2 groups is of clinical importance since in individual patients it gives insight into the safe administration of pyrazolone and aspirin-like drugs.