What is the Mellanby Effect associated with?

The Mellanby Effect refers to the phenomenon where the effects of a drug, particularly alcohol, vary with the concentration of the drug in the bloodstream at different times. Specifically, it describes how the degree of intoxication can change based on whether a person is ascending to or descending from the peak blood alcohol concentration. This means that the same blood alcohol level can lead to different effects depending on whether the individual has just commenced drinking or is coming down from that peak.

In this context, the correct choice pertains to the sensitivity of the body to a drug, which directly correlates with the levels of that drug in the bloodstream. Intoxicating effects differ based on the current blood level, even if that level is statistically the same. As for the other options, they relate to different pharmacological principles or factors affecting drug action but do not specifically define the Mellanby Effect itself.