What term is used for drugs that work by attaching to the same receptor as the natural substrate and mimicking its effect?

Drugs that attach to the same receptor as the natural substrate and mimic its effects are referred to as agonists. Agonists activate the receptor by binding to it, leading to a biological response that closely resembles the action of the natural substrate. This mimicking effect is crucial in pharmacology as it can enhance or replicate the physiological functions that the natural ligand (substrate) is responsible for in the body.

For example, medications that are agonists can be used to treat conditions by simulating the effect of naturally occurring substances in the body, thereby contributing to therapeutic outcomes. An example is morphine, which acts as an agonist at opioid receptors, producing effects similar to those of endorphins.

In contrast, antagonists block receptors and prevent the natural substrate from exerting its effects, while inhibitors typically decrease the activity of enzymes rather than mimicking receptor activity. Modulators can either enhance or inhibit receptor function but do not strictly mimic the effect of a natural substrate in the same manner as an agonist. This distinction clarifies why the term "agonists" is specifically used for drugs that activate receptors by mimicking natural ligands.