Drug allergies may be more frequent in systemic lupus erythematosus than in rheumatoid arthritis.

OBJECTIVE

To measure the frequency of drug allergies in patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), and register the causal drug, the type, and severity of the reaction.

MATERIAL AND METHODS

Direct interview and chart review in patients with RA and SLE were conducted. We registered demographic data, drug allergies, the causal drug, how causality was assessed, and the type and severity of the allergic reaction. We include as drug allergies only those cases in which the result of exposure and re-exposure was known or in which a physician evaluating the original event established the causality link with the suspected drug. Differences between groups were assessed by chi test.

RESULTS

Two hundred ninety-three RA and 58 patients with SLE were included. Fifty-three of the patients with RA (18%) and 20 of the patients with SLE (34.3%, P = 0.049) reported drug allergies. Most of them presented skin rash as their clinical expression of allergy (73%); anaphylaxis was reported in 4 cases (5%). Allergy to sulfa drugs is found more frequently in SLE (P = 0.0079). No differences were found when comparing the frequency of other drug allergies, such as penicillin and metamizole.

DISCUSSION

Drug allergies are more frequent in SLE than in RA. Sulfa drugs are still the most frequent cause of drug allergies in SLE. Allergies because of drugs forbidden in the United States but easily available in specific ethnic groups are frequent in patients with SLE and RA. Their specific consumption must be intentionally assessed in cases of suspected drug allergies.