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Local Anesthetics — Pharmacology

General & Dental Pharmacology • NEET MDS Study Guide • AI-Generated Notes

⭐ High-Yield Facts for Exam

  • Mechanism = Na⁺ channel blockade.
  • Esters → pseudocholinesterase (plasma).
  • Amides → liver.
  • pKa determines onset (lower = faster).
  • Lipid solubility = potency; protein binding = duration.

Local Anesthetics — Pharmacology

Mechanism

LAs block voltage-gated sodium channels on the internal side, preventing depolarisation and nerve conduction.

Classes & Metabolism

  • Esters (procaine, benzocaine) — metabolised by plasma pseudocholinesterase; higher allergy potential (PABA).
  • Amides (lidocaine, articaine, bupivacaine) — metabolised in the liver (articaine also by plasma esterases).

Key Physicochemical Links

  • pKa → onset (lower pKa = more unionised drug = faster onset).
  • Lipid solubility → potency; protein binding → duration.

Exam Tips ⭐

Esters = pseudocholinesterase; amides = liver; lower pKa = faster onset; mechanism = Na⁺ channel block.

📝 Practice MCQs — Local Anesthetics — Pharmacology

Q1. Amide local anesthetics are primarily metabolised in the:
A. Plasma
B. Liver
C. Kidney
D. Lungs
Show Answer
✅ Answer: B
Amides are metabolised hepatically (articaine also by plasma esterases).
Q2. Local anesthetics act by blocking:
A. Potassium channels
B. Sodium channels
C. Calcium channels
D. GABA receptors
Show Answer
✅ Answer: B
LAs block voltage-gated Na⁺ channels.
Q3. A lower pKa of a local anesthetic results in:
A. Slower onset
B. Faster onset
C. Longer duration
D. Higher potency
Show Answer
✅ Answer: B
Lower pKa means more unionised drug → faster onset.
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