A 50 years old hypertensive male cardiac patient, who is on anticonvulsant treatment, developed following rash on right hand. Most probable drug responsible for it is-
**Core Concept**
The patient's rash is likely a drug reaction, specifically a type of hypersensitivity reaction, which is a common side effect of certain medications, including anticonvulsants. This reaction is mediated by the immune system and can manifest in various ways, including skin rashes, fever, and other systemic symptoms.
**Why the Correct Answer is Right**
The most probable drug responsible for the rash in this patient is likely phenytoin, an anticonvulsant medication. Phenytoin is known to cause a range of hypersensitivity reactions, including a characteristic exanthematous rash, often referred to as "phenytoin rash." This reaction is thought to be mediated by the immune system's response to the drug, which can lead to the activation of T-cells and the release of pro-inflammatory cytokines. The rash typically appears within 2-8 weeks of starting the medication and can be accompanied by systemic symptoms such as fever and lymphadenopathy.
**Why Each Wrong Option is Incorrect**
**Option A:** Carbamazepine is another anticonvulsant medication, but it is less commonly associated with a characteristic exanthematous rash compared to phenytoin.
**Option B:** Valproate is a third anticonvulsant medication, but it is not typically associated with a hypersensitivity reaction in the form of an exanthematous rash.
**Option C:** The patient's anticonvulsant treatment is not specified, but if it were carbamazepine or valproate, these would be less likely causes of the rash compared to phenytoin.
**Clinical Pearl / High-Yield Fact**
It's essential to recognize the characteristic "phenytoin rash" in patients taking anticonvulsant medications, as it may indicate a hypersensitivity reaction that requires prompt discontinuation of the medication and potentially alternative anticonvulsant therapy.
**Correct Answer: C. Phenytoin**