Fixed drug eruptions can be seen more frequently with –
**Core Concept**
Fixed drug eruptions (FDEs) are a type of cutaneous adverse reaction that occurs in response to certain medications, leading to localized skin lesions. These eruptions are characterized by well-defined, round or oval-shaped patches that recur at the same site with each subsequent exposure to the offending drug.
**Why the Correct Answer is Right**
The correct answer is **Sulphonomamides**. Sulphonamides, a class of antimicrobials, are known to cause FDEs in a significant number of patients. The pathophysiology of FDEs is thought to involve the release of histamine and other mediators from mast cells, leading to vasodilation and increased permeability of blood vessels. Sulphonamides are metabolized by the liver enzyme N-acetyltransferase 2 (NAT2), and individuals with rapid NAT2 acetylation are more likely to experience FDEs.
**Why Each Wrong Option is Incorrect**
**Option A:** Penicillins are not commonly associated with FDEs. While penicillins can cause various skin reactions, such as urticaria or angioedema, FDEs are relatively rare with this class of antibiotics.
**Option B:** Cephalosporins are a related class of antibiotics, but they are not as commonly linked to FDEs as sulphonamides. Some cephalosporins may cause skin reactions, but FDEs are not a typical adverse effect.
**Option C:** Phenobarbital is a barbiturate used primarily for seizure control and sedation. While barbiturates can cause various adverse effects, FDEs are not a well-documented risk associated with phenobarbital.
**Clinical Pearl / High-Yield Fact**
When evaluating a patient with a skin eruption, it is essential to consider the temporal relationship between the onset of the eruption and the initiation of any new medications, including antibiotics and sulphonamides. A thorough review of the patient's medication history can help identify potential culprits and guide appropriate management.
**Correct Answer:** B. Cephalosporins