Which anesthetic has the widest duration variability based on injection technique?

Which anesthetic has the widest duration variability based on injection technique?

• A. Prilocaine
• B. Lidocaine
• C. Bupivacaine
• D. Mepivacine

Answer: (A)

Duration of a local anesthetic depends on how quickly the drug is removed from the site, which in turn is driven by tissue blood flow and diffusion. The injection technique matters because it changes local perfusion and the effect of vasoconstrictors, producing different durations of action for the same drug. Prilocaine is particularly variable because its intrinsic vasodilatory effect is relatively low compared with some others, so adding or omitting a vasoconstrictor causes large swings in how long the block lasts. In highly vascular areas or without a vasoconstrictor, prilocaine is cleared quickly, yielding a shorter duration. When a vasoconstrictor is used or when diffusion into less vascular tissue occurs, its duration can extend substantially. This combination makes its duration far more variable across injection techniques than the other commonly used anesthetics, which tend to have more consistent durations across techniques.

Duration of a local anesthetic depends on how quickly the drug is removed from the site, which in turn is driven by tissue blood flow and diffusion. The injection technique matters because it changes local perfusion and the effect of vasoconstrictors, producing different durations of action for the same drug.

Prilocaine is particularly variable because its intrinsic vasodilatory effect is relatively low compared with some others, so adding or omitting a vasoconstrictor causes large swings in how long the block lasts. In highly vascular areas or without a vasoconstrictor, prilocaine is cleared quickly, yielding a shorter duration. When a vasoconstrictor is used or when diffusion into less vascular tissue occurs, its duration can extend substantially. This combination makes its duration far more variable across injection techniques than the other commonly used anesthetics, which tend to have more consistent durations across techniques.