Selective adverse reactions to diflunisal

Abstract

Background and objective: Diflunisal is a difluorophenyl derivative of salicylic acid. We report two patients who presented immediate adverse reactions to diflunisal (Dolobid) that consisted of generalized urticaria and chest tightness.

Methods: Diflunisal was conjugated to human serum albumin in order to perform in vivo and in vitro tests (skin prick and intradermal tests, leukocyte histamine release, and RAST). The patients were challenged following a single-blind, placebo-controlled oral procedure with diflunisal and other nonsteroidal antiinflammatory drugs.

Results: Skin tests with diflunisal were negative as were leukocyte histamine release tests and RAST in both patients. They tolerated therapeutic doses of aspirin, salsalate, salicylamide, lysine acetylsalicylate, acetaminophen, dipyrone, and propyfenazone. The oral provocation with diflunisal elicited an immediate response at the cumulative dose of 400 mg in both patients.

Conclusion: These are two exceptional cases of selective adverse reactions to diflunisal with good tolerance to other salicylates and nonsteroidal antiinflammatory drugs. Thus, the inhibition of cyclooxygenase does not seem to be the mechanism involved. The pathogenic mechanism implicated in the reaction remains unclear, both idiosyncratic and immunologic mechanisms could explain our patients' adverse responses.