Pharmacodynamics (sometimes described as what a drug does to the body) is the study of the biochemical, physiologic, and molecular effects of drugs on the body and involves receptor binding Drug–Receptor Interactions Receptors are macromolecules involved in chemical signaling between and within cells; they may be located on the cell surface membrane or within the cytoplasm (see table Some Types of Physiologic... read more (including receptor sensitivity), postreceptor effects, and chemical interactions Chemical Interactions Some drugs produce effects without altering cellular function and without binding to a receptor. For example, most antacids decrease gastric acidity through simple chemical reactions; antacids... read more . Pharmacodynamics, with pharmacokinetics Overview of Pharmacokinetics Pharmacokinetics, sometimes described as what the body does to a drug, refers to the movement of drug into, through, and out of the body—the time course of its absorption, bioavailability, distribution... read more (what the body does to a drug, or the fate of a drug within the body), helps explain the relationship between the dose and response Dose-Response Relationships Regardless of how a drug effect occurs—through binding or chemical interaction—the concentration of the drug at the site of action controls the effect. However, response to concentration may... read more , ie, the drug's effects. The pharmacologic response depends on the drug binding to its target. The concentration of the drug at the receptor site influences the drug’s effect.
A drug’s pharmacodynamics can be affected by physiologic changes due to
A disorder or disease
Disorders that affect pharmacodynamic responses include genetic mutations, thyrotoxicosis, malnutrition, myasthenia gravis, Parkinson disease, and some forms of insulin-resistant diabetes mellitus. These disorders can change receptor binding, alter the level of binding proteins, or decrease receptor sensitivity.
Aging tends to affect pharmacodynamic responses through alterations in receptor binding or in postreceptor response sensitivity (see table Effect of Aging on Drug Response Effect of Aging on Drug Response ).
Pharmacodynamic drug–drug interactions result in competition for receptor binding sites or alter postreceptor response.