An antagonist is a substance that inhibits or interferes with the physiological action of another. When it comes to pharmacology, an antagonist is a type of drug that hinders or blocks the actions of a receptor.
- Activates receptor: This option is incorrect because drugs that activate receptors are typically called "agonists" rather than "antagonists."
- Blocks receptor response: This is the correct answer. An antagonist binds to receptors without activating them, effectively blocking or dampening the receptor's response to an agonist. This prevents the endogenous neurotransmitter or hormone from exerting its effect.
- Increases absorption: This is incorrect. Increasing absorption is not related to the primary function of an antagonist, but rather involves the pharmacokinetic properties of a drug.
- Stimulates metabolism: This is incorrect because antagonists do not typically act by stimulating metabolism; they primarily act by blocking receptors.
Thus, an antagonist drug "blocks receptor response," which makes it the correct option.