What does pharmacodynamics study?

Pharmacodynamics is the branch of pharmacology that specifically examines the actions or effects of a drug on the body. This includes how the drug works at the molecular, cellular, and systemic levels, detailing the relationship between drug concentration and its physiological effects. Understanding pharmacodynamics helps in determining the therapeutic effects of drugs, their side effects, and the mechanisms of action, which is essential for developing effective treatment protocols and ensuring patient safety.

In contrast to this concept, other options focus on different aspects of pharmacology. For instance, the effectiveness of herbal treatments pertains more to a specific category of substances rather than the broad principles of pharmacodynamics. Drug interactions with the environment would deal with external factors affecting drug efficacy but does not encompass the direct effects of the drug on the patient's body. Finally, methods of drug delivery refer to how drugs are administered to the body rather than their physiological effects once inside. Hence, option B accurately captures the essence of what pharmacodynamics studies.