[Delayed allergic reaction to amlodipine with a positive lymphocyte transformation test].

Background: Amlodipine is one of the third generation dihydropyridine calcium channel blockers used for hypertension. Mild, moderate and severe reactions have been reported with calcium channel blockers. Cross-reactivity among these drugs has not been established.

Clinical Report: We have presented the case of a patient who developed a delayed pruritic, and erythematous maculopapular skin exanthema after the intake of amlodipine. A positive lymphocyte transformation test (LTT) confirmed the implication of amlodipine in the reaction and showed positivity to another calcium channel blocker, nifedipine, demonstrating cross reactivity.

Conclusion: This is the first reported case of hypersensitivity to amlodipine in which the involvement of the drug is confirmed by a positive TTL. TTL could become a good diagnostic alternative for patients who experience late reactions to amlodipine and possibly cross-reactivity with nifedipine.