Cross-Reactivity in Fixed Drug Eruptions to Tetracyclines

A study1in 1988 documented that tetracycline was the most common cause of fixed drug eruption in Singapore. It is known that patients with such a reaction to tetracycline will cross-react to related drugs.2-4Our study evaluates the degree of cross-sensitivity to doxycycline and minocycline. Subjects and Methods. Sixteen patients clinically confirmed to have developed a fixed drug eruption to tetracycline (as tetracycline hydrochloride) either from history or by challenging with tetracycline were included in the study. Challenge to doxycycline and minocycline was done at least 6 weeks after the last episode of fixed drug eruption in the following order: (1) minocycline hydrochloride, 50 mg; (2) minocycline hydrochloride, 100 mg; and (3) doxycycline hydrochloride, 100 mg. Reaction to any of the drugs is expected to occur within 24 hours. Minocycline hydrochloride (50 mg) was given on day 1. If no reaction occurred, 100 mg was given on