Study found 2% rate: second sulfonamide reaction less common

OB/GYN News, May 15, 2004 by Timothy F. Kirn

SAN FRANCISCO -- Common drugs such as thiazide diuretics, glyburide, and celecoxib can be used safely by most patients who previously had a reaction to sulfonamide antibiotics, Dr. Matt Morgan said at the annual meeting of the American Academy of Allergy, Asthma, and Immunology.

In a study that he presented, only 2% of patients who were reported to have had an allergic-type reaction to an antimicrobial sulfonamide such as trimethoprim-sulfamethoxazole had a reaction to another sulfa drug that was not an antimicrobial.

This is the second study in recent months to report a low rate of such subsequent reactions and to challenge the idea that sulfonamide drugs are absolutely contraindicated for patients who have had an allergic reaction to a sulfonamide antimicrobial. In the prior study. 10% of patients who had an allergic reaction to a sulfonamide antimicrobial had a subsequent reaction to the related drugs; patients who had a previous reaction to penicillin had an even higher risk of a reaction to a nonantimicrobial sulfonamide (N. Engl. J. Med. 349[17]:1628-35, 2003).

Dr. Morgan and his colleagues reviewed 8 years of prescription records from the Parkland Health and Hospital System, Dallas. They identified 247 nonantimicrobial sulfonamide drug prescriptions written for patients identified by the pharmacy as having had an antimicrobial sulfonamide reaction. Each patient received one to three of these drugs: a sulfonylurea, a thiazide, loop diuretic, a carbonic anhydrase inhibitor, a triptan, celecoxib, amprenavir, or dapsone (a sulfone).

Among the 247 prescriptions, 4 led to adverse reactions, none of which was serious or life threatening. A different drug was involved in each case: glyburide, sumatriptan, furosemide, and celecoxib. Overall, 80% of the prescriptions were refilled, providing further evidence that they were well tolerated. "Some of the patients had their prescriptions filled 8, 9, or 10 times," said Dr. Morgan of the University of Texas, Dallas.

The study suggests that prescribing a sulfonamide drug to a patient who reports an allergy is safe, but one should consider how serious the reaction was. The risk is probably too great if the patient reports a prior Stevens-Johnson syndrome incident, based on evidence that such patients are more likely to have cross-reactivity. "In individual patients you have the luxury of asking them about their reaction and what is was like," he added.

Estimates are that 75% of all cutaneous allergic drug reactions are associated with antibiotics of one kind or another, and that reactions occur with 3% of all courses of sulfonamide antimicrobials. In one study, the drugs most commonly associated with a reported reaction were amoxicillin (54.1 per 1,000 patients exposed) and trimethoprim-sulfamethoxazole (33.8 per 1,000) (JAMA 256[24]:3358-63, 1986).

BY TIMOTHY F. KIRN

Sacramento Bureau