Fixed drug eruptions can be seen more frequently with
**Core Concept**
Fixed drug eruptions are a type of cutaneous adverse drug reaction characterized by the appearance of well-defined, round or oval patches of skin that recur at the same site after re-exposure to the offending drug. These lesions are often accompanied by burning, itching, or other dermatological symptoms.
**Why the Correct Answer is Right**
The correct answer is related to the pathophysiology of fixed drug eruptions, which involves the activation of immune cells, such as T lymphocytes and macrophages, in response to the culprit drug. These immune cells release various chemical mediators, including histamine, bradykinin, and leukotrienes, which cause blood vessels to dilate and lead to increased permeability, resulting in the characteristic skin lesions. Some drugs, particularly those that are metabolized by the liver enzyme CYP1A2, are more likely to cause fixed drug eruptions due to their ability to induce this immune response.
**Why Each Wrong Option is Incorrect**
**Option A:**
This option is incorrect because while certain antibiotics can cause drug eruptions, they are not the most common culprits of fixed drug eruptions. Other classes of drugs, such as nonsteroidal anti-inflammatory drugs (NSAIDs) and anticonvulsants, are more frequently associated with this condition.
**Option B:**
This option is incorrect because while phenytoin is an anticonvulsant that can cause various skin eruptions, it is not the most commonly implicated drug in fixed drug eruptions. Other anticonvulsants, such as carbamazepine, are more frequently associated with this condition.
**Option C:**
This option is incorrect because while NSAIDs can cause various skin reactions, including urticaria and angioedema, they are not the most common cause of fixed drug eruptions. Other classes of drugs, such as anticonvulsants and antibiotics, are more frequently associated with this condition.
**Clinical Pearl / High-Yield Fact**
A classic exam trap is to confuse fixed drug eruptions with other types of skin reactions, such as contact dermatitis or urticaria. To avoid this, remember that fixed drug eruptions are characterized by the appearance of well-defined, round or oval patches of skin that recur at the same site after re-exposure to the offending drug.
**Correct Answer:** C.