Pharmacology for NEET-PG
Antiepileptic Drugs for NEET-PG
Antiepileptic pharmacology matches seizure type to the preferred drug and each agent to its mechanism and toxicity, and it is a consistently tested NEET-PG area. The most common question asks for the drug of choice in a named seizure type or clinical setting such as pregnancy, so the seizure-drug map is the essential deliverable. The topic covers sodium channel blockers, calcium channel effects in absence seizures, GABA enhancers, and newer broad-spectrum agents. Examiners emphasise valproate teratogenicity, the enzyme-inducing profile of carbamazepine and phenytoin, the zero-order kinetics of phenytoin, and the specific rashes linked to lamotrigine and carbamazepine. Status epilepticus management and eclampsia prophylaxis with magnesium are recurring high-yield points. The topic also links to obstetrics through folate and pregnancy planning and to dermatology through severe cutaneous reactions. Common traps include giving carbamazepine or phenytoin in absence seizures where they can worsen attacks, forgetting phenytoin saturation kinetics that cause disproportionate toxicity, and overlooking the HLA associations that predict carbamazepine hypersensitivity.
MedNext Academy | 3 min read
Antiepileptic Drugs for NEET-PG
Antiepileptic pharmacology matches seizure type to the preferred drug and each agent to its mechanism and toxicity, and it is a consistently tested NEET-PG area. The most common question asks for the drug of choice in a named seizure type or clinical setting such as pregnancy, so the seizure-drug map is the essential deliverable. The topic covers sodium channel blockers, calcium channel effects in absence seizures, GABA enhancers, and newer broad-spectrum agents. Examiners emphasise valproate teratogenicity, the enzyme-inducing profile of carbamazepine and phenytoin, the zero-order kinetics of phenytoin, and the specific rashes linked to lamotrigine and carbamazepine. Status epilepticus management and eclampsia prophylaxis with magnesium are recurring high-yield points. The topic also links to obstetrics through folate and pregnancy planning and to dermatology through severe cutaneous reactions. Common traps include giving carbamazepine or phenytoin in absence seizures where they can worsen attacks, forgetting phenytoin saturation kinetics that cause disproportionate toxicity, and overlooking the HLA associations that predict carbamazepine hypersensitivity.
Antiepileptic pharmacology matches seizure type to the preferred drug and each agent to its mechanism and toxicity, and it is a consistently tested NEET-PG area. The most common question asks for the drug of choice in a named seizure type or clinical setting such as pregnancy, so the seizure-drug map is the essential deliverable. The topic covers sodium channel blockers, calcium channel effects in absence seizures, GABA enhancers, and newer broad-spectrum agents. Examiners emphasise valproate teratogenicity, the enzyme-inducing profile of carbamazepine and phenytoin, the zero-order kinetics of phenytoin, and the specific rashes linked to lamotrigine and carbamazepine. Status epilepticus management and eclampsia prophylaxis with magnesium are recurring high-yield points. The topic also links to obstetrics through folate and pregnancy planning and to dermatology through severe cutaneous reactions. Common traps include giving carbamazepine or phenytoin in absence seizures where they can worsen attacks, forgetting phenytoin saturation kinetics that cause disproportionate toxicity, and overlooking the HLA associations that predict carbamazepine hypersensitivity.
Key points
- **Absence seizures:** Ethosuximide, which blocks T-type calcium channels, is first-line; valproate covers coexisting generalised seizures.
- **Focal and generalised tonic-clonic seizures:** Carbamazepine, lamotrigine, and levetiracetam are common first-line options; valproate is broad-spectrum but teratogenic.
- **Phenytoin kinetics:** Shows zero-order saturation kinetics, so small dose increases can cause disproportionate toxicity such as nystagmus and ataxia.
- **Valproate:** Broad-spectrum but hepatotoxic and highly teratogenic, causing neural tube defects; avoided in women of childbearing potential where possible.
- **Carbamazepine:** Enzyme inducer that can cause hyponatraemia, agranulocytosis, and severe skin reactions linked to HLA-B*15:02 in certain populations.
- **Lamotrigine:** Requires slow titration to reduce the risk of Stevens-Johnson syndrome; valproate raises its levels.
- **Levetiracetam:** Broad-spectrum with few interactions and renal clearance; behavioural and mood effects are the main adverse effects.
- **Status epilepticus:** Intravenous lorazepam first, then fosphenytoin, valproate, or levetiracetam; refractory cases need anaesthetic agents.
- **Eclampsia:** Magnesium sulphate is the drug of choice for seizure prophylaxis and treatment, not standard antiepileptics.
- **Enzyme induction:** Phenytoin, carbamazepine, and phenobarbital induce hepatic enzymes and can lower oral contraceptive efficacy.
- **Phenytoin adverse effects:** Gingival hyperplasia, hirsutism, coarse facies, megaloblastic anaemia, and cerebellar signs at toxic levels.
Frequently Asked Questions
What is the drug of choice for absence seizures?
Ethosuximide for pure absence seizures. When absence coexists with generalised tonic-clonic seizures, valproate is preferred because it covers both.
Why is valproate avoided in women of childbearing age?
Valproate carries a high risk of neural tube defects and neurodevelopmental harm. Safer alternatives such as lamotrigine or levetiracetam are preferred where seizure control allows.
Why does phenytoin cause sudden toxicity?
Phenytoin follows zero-order kinetics near therapeutic levels, so its metabolism saturates. A small dose rise can push levels sharply up, producing nystagmus, ataxia, and slurred speech.
What is used for status epilepticus first?
A benzodiazepine, usually intravenous lorazepam, is first-line. If seizures continue, load with fosphenytoin, valproate, or levetiracetam.
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