Fixed drug eruption (FDE) is characterised by recurrence at the same site on re-exposure. The causative drug most classically associated with FDE is:

• A Trimethoprim-sulfamethoxazole (cotrimoxazole) ✓
• B Amoxicillin
• C Metformin
• D Atenolol

Explanation

Trimethoprim-sulfamethoxazole (cotrimoxazole/co-trimoxazole) is the single most common cause of fixed drug eruption in India and globally. NSAIDs (particularly phenylbutazone, oxicams), tetracyclines, metronidazole, and dapsone are also frequent culprits. The FDE mechanism involves resident CD8+ effector memory T cells in the dermis that are activated by drug presentation, releasing IFN-gamma and causing epidermal cell death and post-inflammatory hyperpigmentation at the same site. Amoxicillin more commonly causes maculopapular exanthem or urticaria.

Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.