Delayed reactions to radio-contrast media (RCM) with positive skin tests are rare. We report the study of a series of 15 patients who presented delayed reactions to RCM, with an analysis of the clinical features and the results of standardized drug skin tests. Patch tests were performed with RCM and iodized antiseptics (IAs). If negative, prick tests were performed, followed by intradermal tests (IDTs), then intravenous administration under hospital surveillance. The main clinical features were maculopapular rashes or a macular rubella-like rashes. Patch tests were positive with RCM in 2 of 15 cases and with IAs in 4 of 15 cases. All the prick tests were negative. IDTs were positive at 24 h in 8 of 15 cases. 5 of 12 patients had a non-severe relapse of the rash upon receiving an RCM despite clearly negative skin tests with the readministered RCM. Visipaque cross-reacted with Iopamiron, Iomeron, Telebrix, Omnipaque, Xenetix and Hexabrix. Omnipaque cross-reacted with Hexabrix and Iopamiron. IDTs with delayed readings are of better value than patch tests in such patients. The readministration of RCM with negative IDTs must be performed with progressive amounts under hospital surveillance. Cross-reactions between various classes of RCM are frequent. The responsible epitopes are unknown. Iodine itself could be involved.
The results suggest that topical morphine cannot be an alternative to morphine administered by other routes (subcutaneously or orally) in painful chronic skin ulcers. Stimulation of peripheral morphine receptors by systemic morphine could explain the difference between these results and those of previous studies.
Allergic contact dermatitis caused by acyclovir is rare. We report the 5th case of systemic acyclovir reaction subsequent to acyclovir contact dermatitis, with investigations made to determine an alternative antiviral treatment. A 23-year-old woman, after dermatitis while using Zovirax cream, went on to develop urticaria after oral acyclovir. Patch tests were performed with the components of Zovirax cream (acyclovir, propylene glycol and sodium lauryl sulfate) and with other antiviral drugs. Patch tests were positive to Zovirax cream, acyclovir, valacyclovir and propylene glycol. Patch and prick tests with famciclovir were negative, but its oral administration caused an itchy erythematous dermatitis on the trunk and extremities. Our patient developed a systemic acyclovir reaction subsequent to acyclovir allergic contact dermatitis, with cross-reactions to valacyclovir and famciclovir. Their common chemical structure is the 2-aminopurine nucleus. It is probably this part of the molecule that provokes both contact allergy and systemic reactions. The only antiviral drugs not having this core are foscarnet and cidofovir, and these could therefore be alternatives.
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