Question

How adrenaline prolong duration of a local anesthetics?

• A. Increasing the permeability
• B. Local vasoconstriction
• C. Changing the pH
• D. Inhibition of its metabolism

Hint:

Adrenaline = Vasoconstrictor = Less blood flow = Longer numbing.

Answer 1

The Correct Option is B

Step 1: Concept
Local anesthetics are often combined with vasoconstrictors to enhance their clinical efficacy.

Step 2: Meaning
Duration of action depends on how long the anesthetic remains in contact with the nerve fibers before being carried away by the blood.

Step 3: Analysis
Adrenaline (epinephrine) acts on alpha-adrenergic receptors to cause narrowing of the blood vessels (vasoconstriction) at the injection site. This reduced blood flow slows down the systemic absorption of the anesthetic.

Step 4: Conclusion
By keeping the drug localized for a longer period through vasoconstriction, adrenaline successfully prolongs the duration of anesthesia.

Final Answer: (B)