An agent with a Blood: Gas partition coefficient of 12.0 is characterized how?

The Blood: Gas partition coefficient is a crucial factor in understanding the pharmacokinetics of inhaled anesthetics. A coefficient of 12.0 indicates a high solubility of the agent in blood relative to the gas phase. This means that the agent will preferentially dissolve into the blood rather than remain in the gas form.

Agents with a high Blood: Gas partition coefficient are characterized by their slow onset of action because they take longer to saturate the blood before sufficient amounts can reach the brain to exert their anesthetic effect. This slow build-up results in a longer time to achieve the desired level of anesthesia, which is generally not desirable.

Furthermore, a high Blood: Gas partition coefficient typically correlates with lower potency in terms of minimum alveolar concentration (MAC). In other words, while the agent is present in higher concentrations in the blood, it may not effectively lead to a potent anesthetic state within the target tissues quickly, as it takes time to equilibrate.

Given all these considerations, an agent with a Blood: Gas partition coefficient of 12.0 is indeed characterized as lacking potency and building up slowly in the body, supporting the chosen answer.