Topical provocation of fixed drug eruption

Area of Science:

• Dermatology
• Pharmacology
• Allergy and Immunology

Background:

• Fixed drug eruption (FDE) diagnosis traditionally relies on systemic provocation, which carries risks.
• Developing safer diagnostic methods for FDE is crucial for patient management.

Purpose of the Study:

• To evaluate the efficacy of topical drug provocation for diagnosing fixed drug eruptions (FDE).
• To compare different vehicles and concentrations for topical FDE testing.
• To investigate cross-reactivity among phenazone derivatives in FDE patients.

Main Methods:

• 24 patients with established FDE were tested with suspected drugs (1-10% concentrations) in petrolatum, ethanol, or DMSO.
• Testing was performed on both previous FDE lesion sites and clinically normal skin.
• Cross-reactivity testing with phenazone derivatives was conducted on three patients.

Main Results:

• Local FDE provocation occurred in 18 of 24 patients, exclusively on previous lesion sites.
• Vehicle choice impacted results; DMSO enhanced sensitivity for certain drugs (sulfamethoxazole, trimethoprim).
• Topical phenazone triggered FDE in all three tested patients, indicating cross-reactivity.

Conclusions:

• Topical drug provocation is a viable diagnostic tool for FDE.
• Testing on previous FDE sites increases diagnostic accuracy.
• Optimizing vehicle penetration can enhance the sensitivity of topical FDE testing.