Selectivity is defined as

Selectivity is defined as

• A. The ability to interact with multiple targets
• B. A measure of potency
• C. Solely interacting with its intended target
• D. A measure of how well it matches its receptor's three-dimensional shape

Answer: (C)

Selectivity means how preferentially a drug acts at its intended target compared with other possible targets. When a drug is highly selective, it binds and produces its primary effect at the desired receptor with minimal activity elsewhere. That makes the idea of targeting only the intended receptor the best way to define selectivity, even though in reality some off-target interactions can occur at higher doses. The other ideas describe different concepts: interacting with multiple targets would indicate low selectivity or polypharmacology; potency is about the amount of drug needed to produce an effect, not how specifically it targets one receptor; and how well it fits the receptor’s three-dimensional shape relates to affinity or binding fit at a receptor, not across multiple targets.

Selectivity means how preferentially a drug acts at its intended target compared with other possible targets. When a drug is highly selective, it binds and produces its primary effect at the desired receptor with minimal activity elsewhere. That makes the idea of targeting only the intended receptor the best way to define selectivity, even though in reality some off-target interactions can occur at higher doses.

The other ideas describe different concepts: interacting with multiple targets would indicate low selectivity or polypharmacology; potency is about the amount of drug needed to produce an effect, not how specifically it targets one receptor; and how well it fits the receptor’s three-dimensional shape relates to affinity or binding fit at a receptor, not across multiple targets.