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Anesthesia · single question

What happens when a local anesthetic solution is buffered (e.g., with sodium bicarbonate)?

  1. The pH of the solution increases
  2. Onset of pulpal anesthesia is delayed
  3. The anesthetic becomes more ionized and less lipid-soluble
  4. Duration of action is shortened
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Correct answer: A. The pH of the solution increases

  • A. Correct – buffering raises pH toward physiologic, increasing the un-ionized (lipid-soluble) fraction → FASTER onset and less injection sting.
  • B. Incorrect – buffering speeds onset, it does not delay it.
  • C. Incorrect. Buffering raises pH, which increases the proportion of the un-ionized (lipid-soluble) base, speeding nerve penetration — the opposite of this statement.
  • D. Incorrect – duration is essentially unchanged; the main benefit is faster, more comfortable onset.

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