What kind of drug effect involves the entire body, such as the action of a blood pressure lowering agent?

A systematic effect refers to the impact a drug has on the entire body rather than just a localized area. This term is particularly relevant for medications that are designed to affect multiple organs and systems within the body. For instance, a blood pressure lowering agent works systematically by influencing cardiovascular functions throughout the body, promoting a reduction in blood pressure by acting on various systems such as the heart and blood vessels.

In contrast, a localized effect would only impact a specific area, such as applying a topical cream on the skin that targets localized irritation. Skeletal effect pertains more to actions related to the muscles and bones, and chronic effect usually refers to the long-term consequences of medication use rather than their immediate or broad actions throughout the body. Thus, the systematic effect encompasses the comprehensive influence of certain drugs, making it the correct choice in this question.