antiepileptic drugs

1. Phenytoin

• Mechanism of Action (MoA): Blocks voltage-gated sodium channels (specifically at high frequency of firing). Also possesses anti-arrhythmic properties.

• Side Effects:

• Gingival hyperplasia (gum hypertrophy, most common in children)

• Hirsutism

• Fetal malformations (e.g., cleft palate / teratogenicity)

• Skin rash

• Inhibition of insulin release (aggravates diabetes)

• Extra Notes & High-Yield Exam Points:

• Uses: Effective for all types of seizures except absence and myoclonic seizures. Also used for trigeminal neuralgia and cardiac arrhythmias (ventricular/supraventricular).

• Drug Interactions: It is a liver enzyme inducer (decreases efficacy of oral contraceptives and other antiepileptics). Carbamazepine enhances its metabolism, while Valproate displaces it from plasma proteins (increasing its effect).

2. Carbamazepine

• Mechanism of Action (MoA): Blocks sodium channels (similar to phenytoin).

• Side Effects:

• Drowsiness, nausea, vomiting, skin rash

• Aplastic anemia and hepatic dysfunction (requires routine blood counts and liver function tests)

• Extra Notes & High-Yield Exam Points:

• Uses: First-line for partial and generalized tonic-clonic seizures. Also used for trigeminal neuralgia and manic depression (bipolar disorder).

• Enzyme effect: Enhances the metabolism of phenytoin.

3. Valproic Acid (Valproate)

• Mechanism of Action (MoA): Inhibits sodium channels and enhances GABA synthesis / inhibits its degradation.

• Side Effects:

• Changes in appetite, skin rash, and alopecia (hair loss)

• Fulminant hepatitis (rare but potentially fatal, especially in children below 2 years of age)

• Extra Notes & High-Yield Exam Points:

• Broad Spectrum: Highly versatile; used for all types of seizures (including absence and myoclonic). Also used for manic depression.

• Displacement interaction: Can displace phenytoin from plasma protein binding sites, increasing free phenytoin levels.

4. Ethosuximide

• Mechanism of Action (MoA): Inhibits T-type calcium channels.

• Side Effects:

• GIT reactions: Nausea and vomiting

• CNS effects: Drowsiness, euphoria, headache, and Parkinsonian-like syndrome

• Skin reactions

• Extra Notes & High-Yield Exam Points:

• Drug of Choice (DOC): Specifically indicated and most important for absence seizures (petit mal).

5. Diazepam (Benzodiazepines group)

• Mechanism of Action (MoA): Enhances GABA binding to receptors, increasing the frequency of chloride channel opening.

• Side Effects:

• Sedation

• Tolerance with chronic use and physical dependence (addiction)

• Withdrawal: Sudden cessation can precipitate grand mal seizures.

• Extra Notes & High-Yield Exam Points:

• Status Epilepticus: First-line therapy (given I.V. slowly over 2 minutes) for status epilepticus.

6. Phenobarbital (Barbiturate group)

• Mechanism of Action (MoA): Enhances GABA-mediated inhibition by increasing the duration of chloride channel opening.

• Side Effects:

• Marked sedation / CNS depression

• Tolerance, dependence, and addiction

• Withdrawal seizures upon abrupt discontinuation

• Extra Notes & High-Yield Exam Points:

• Used as a step in status epilepticus management if diazepam/phenytoin fail (often third-line).

7. Felbamate (New Generation)

• Mechanism of Action (MoA): Blocks both calcium and sodium channels.

• Side Effects:

• Aplastic anemia and hepatic failure

• Extra Notes & High-Yield Exam Points:

• Indications: Broad-spectrum anticonvulsant restricted strictly to drug-resistant cases and Lennox-Gastaut syndrome (characterized by multiple seizure types, mental retardation, and drug resistance)⭐️⭐️⭐️⭐️

8. Topiramate (New Generation)

• Mechanism of Action (MoA): Blocks calcium and sodium channels, and increases chloride channel opening at GABA receptors.

• Side Effects:

• CNS disturbances: Dizziness, ataxia, nervousness

• Teratogenic (strictly avoided during pregnancy)

• Extra Notes & High-Yield Exam Points:

• Indications: Used for treatment-resistant epilepsy and Lennox-Gastaut syndrome.

High yield points

1. A staticus minutes and was given diazepam, phenytoin, and phenobarbital respectively. Which one of the following drugs is given finally?

A. Thiopental

B. Felbamate

C. Valproic acid

Answer: A

2. A patient has Lennox Gastaut syndrome. Which drug is recommended in his condition?

A. Felbamate

B. Ethosuximide

C. Valproic acid

D. Carbamazepine

Answer: A

3. A patient came to the ER due to grand mal seizure lasting more than 10 minutes. Which drug is the first line of treatment in this case?

A. Phenytoin

B. Phenobarbital

C. Valproic acid

D. Diazepam

Answer: D

4. Which one of the following is the mechanism of action of benzodiazepines?

A. Enhance Gaba binding and opening of chloride channel

B. Increase Na influx

C. Increase Ca influx

D. Enhance Gaba binding and closure of chloride channel

Answer: A

5. A patient has Lennox Gestaut syndrome. Which drug is recommended in his condition?

A. Felbamate

B. Ethosuximide

C. Valproic acid

D. Carbamazepine

Answer: A

New antiepileptic drugs [Felbamate, Topiramate] are used in treating Lennox-Gestaut syndrome

6. A patient had a seizure which lasted for more than 10 minutes. What’s the first line of treatment?

A. Phenytoin

B. Thiopental

C. Diazepam

D. Felbamate

Answer: C