Drugs used to bind to receptors, inhibiting its natural function and blocking a message are called

We need to identify the type of drugs that bind to receptors, inhibit their natural function, and block a message.

Drugs interact with receptors in different ways, including agonists, antagonists, allosteric modulators, and lead compounds. Agonists bind to receptors and mimic the natural messenger, activating the receptor and producing a biological response. Antagonists bind to receptors and block the natural messenger from binding, thereby inhibiting the receptor's natural function without activating it. Allosteric modulators bind at a site different from the active site, modifying the receptor's response. Lead compounds are chemical compounds that show potential therapeutic activity and serve as starting points for drug development.

The question describes drugs that "bind to receptors, inhibiting its natural function and blocking a message." This is the exact definition of antagonists.

Hence, the correct answer is Option A.