Which ultrashort-acting barbiturate produces 5 to 10 minutes of anesthesia and may be used in sight hounds due to rapid redistribution and metabolism?

• A. Thiopental
• B. Methohexital
• C. Etomidate
• D. Propofol

Answer: (B)

Ultrashort-acting barbiturates produce a brief lapse of anesthesia because they rapidly enter the brain and are then quickly cleared as they redistribute to and are metabolized by other tissues. Methohexital is particularly fast in this regard, being cleared very quickly by hepatic metabolism and extrahepatic pathways and exiting the brain promptly as it redistributes. This combination yields a short anesthetic window of roughly 5 to 10 minutes, which is ideal for very brief procedures. In sight hounds, this rapid clearance helps ensure a quick return to consciousness with minimal residual sedation, making methohexital a preferred choice for induction when a short duration is desired.

Thiopental also acts quickly, but its recovery can be more prolonged due to deeper tissue storage and slower redistribution in some dogs, leading to a longer tail of sedation. Etomidate and propofol are not barbiturates, so they don’t fit the category described here, even though they can be used for induction with their own distinct pharmacokinetic profiles.