Non-steroidal anti-inflammatory drugs (NSAIDs) are one of the main aetiologies of severe anaphylaxis. The prevalence of severe anaphylaxis because of NSAIDs registered by the Allergy Vigilance Network over 2003–2004 (1) was 13%.
A 75-year-old man with a previous history of osteoarthrosis, sporadically treated with various NSAIDs, took aceclofenac (100 mg/day). Clinical symptoms appeared 2 h after the second dose intake. Symptoms included itching in legs without cutaneous lesions, palpebral and labial oedema, and dyspnea. The patient was treated with methylprednisolone and dexchlorpheniramine immediately. After this episode, therapeutic doses of diclofenac as well as other anti-inflammatory, drugs, such as Ibuprofen and Metamizol, were tolerated.
Cutaneous tests with aceclofenac, both prick and intradermal tests (30 mg/ml and 3 g/ml, respectively), were performed. The result was positive for the intradermal test. Five controls were tested, with negative results.
Aceclofenac, [o-(2,6-dichloroanilino)phenylacetate glycolic acid ester, is a NSAIDs of the phenylacetic acid group (2). After its absorption, the drug is hydrolyzed to diclofenac (3), also from the phenylacetic acid group (Fig. 1). Alclofenac and fenclofenac, two NSAIDs with similar chemical structure to aceclofenac, were withdrawn in the late 1970s and 1980s because of the high incidence of rash (4).
The most common hypersensitivity reaction described with aceclofenac is hypersensitivity vasculitis (4). A case of photoallergic contact dermatitis (5) and another one of exudative erythema multiforme (6), both related to aceclofenac, have been reported.
Two of these cases, showed no cross-reaction between aceclofenac and diclofenac, as occurred in the case reported above. It suggests that cross-reactions among phenylacetic-derived NSAIDs are not so frequent.
To our knowledge, this is the first report of an anaphylactic reaction after the intake of aceclofenac. Clinical features and cutaneous test with aceclofenac suggest an immunoglobulin E (IgE)-mediated mechanism.