A young male, Farhan suffers from a seizure disorder which is characterized by tonic rigidity of limbs followed in 20-30 sec by tremors progressing to massive jerking of the body. This clonic phase lasts for 1–3 min. The anti–seizure drug of choice for this patient is :

**Core Concept**
Farhan's seizure disorder, characterized by tonic rigidity followed by clonic jerking, is indicative of a generalized tonic-clonic seizure (GTC). This type of seizure involves both hemispheres of the brain and is often associated with an imbalance of excitatory and inhibitory neurotransmitters.

**Why the Correct Answer is Right**
The anti-seizure drug of choice for generalized tonic-clonic seizures is **Phenytoin** (Option C). Phenytoin works by blocking voltage-gated sodium channels in the neuronal membrane, which stabilizes the threshold against hyperexcitability caused by excessive stimulation. This action is particularly effective in reducing the occurrence of GTC seizures. Additionally, Phenytoin has a rapid onset of action and is effective in both acute and chronic management of seizures.

**Why Each Wrong Option is Incorrect**
**Option A:** Carbamazepine is primarily used for partial seizures and trigeminal neuralgia, and is not the first-line treatment for generalized tonic-clonic seizures.
**Option B:** Valproate is a broad-spectrum antiepileptic drug, but it is not the preferred choice for GTC seizures due to its side effect profile and potential for hepatotoxicity.
**Option D:** Lorazepam is a benzodiazepine used as an acute treatment for seizures, but it is not a first-line medication for long-term management of GTC seizures.

**Clinical Pearl / High-Yield Fact**
Phenytoin is a classic example of a "dose-dependent" medication, meaning that its efficacy and toxicity are closely related to plasma concentrations. Therefore, monitoring of serum levels is crucial to avoid toxicity and ensure optimal seizure control.

**Correct Answer: C. Phenytoin**

✓ Correct Answer: D. Valproic acid