In pharmacology, what does a high therapeutic index indicate?

A high therapeutic index indicates a large difference between the effective dose of a drug and its lethal dose, which is an important factor in determining the safety of a medication. This means that there is a wide margin within which the drug can be administered effectively without causing harm. In practical terms, a high therapeutic index suggests that the drug can be used at various doses to achieve the desired therapeutic effect without reaching toxic levels, making it safer for patients.

In contrast, the other options do not accurately represent the implications of a high therapeutic index. While potency involves the amount of drug needed for effect, a high therapeutic index specifically relates to safety rather than potency alone. Describing a drug as unsafe contradicts the meaning of a high therapeutic index, which is centered on safety and effectiveness. Lastly, the idea that a drug has no significant effects at any dose does not apply, as a therapeutic index implies that the drug is effective within a specific range of doses.