Ethosuximide

• Ethosuximide is effective in treating absence seizures by reducing abnormal brain activity.
• It blocks T-type calcium channels in neurons, stabilizing electrical activity.

Chemical Formula:

• C₇H₁₁NO₂

Mechanism of Action:

• Selectively inhibits T-type calcium channels
• Suppresses thalamic burst firing → prevents spike-wave discharges

Therapeutic Uses:

• First-line agent for absence seizures

Side Effects:

• GI upset (nausea, vomiting)
• Drowsiness
• Hiccups
• Rare: SJS, blood dyscrasias

SAR of Succinimides (Ethosuximide):

1. Succinimide ring (pyrrolidine-2,5-dione):

   • Essential for activity.
   • Substitution at position 3 with an ethyl group increases potency.

2. Alkyl side chain (ethyl group):

   • Improves lipophilicity and CNS penetration.

3. No aromatic ring:

   • Differs from other AEDs; contributes to selectivity for absence seizures.

4. Ring substitutions:

   • Minimal modification tolerated without loss of activity.

Synthesis of Ethosuximide:

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