Which term is defined as the dose determined to be safe for use and achieve the desired effect; determined by dividing the lethal dose by the effective dose?

Which term is defined as the dose determined to be safe for use and achieve the desired effect; determined by dividing the lethal dose by the effective dose?

• A. Therapeutic index
• B. Potency
• C. Half-life
• D. Threshold dose

Answer: (A)

The idea being tested is the safety margin of a drug, captured by the therapeutic index. The therapeutic index is the ratio of the dose that can be lethal to subjects (LD50) to the dose that produces the desired effect (ED50). This shows how much separation there is between effective and toxic doses. A larger therapeutic index means a wider safety margin, so the drug can be used with less risk of toxicity at therapeutic doses. The definition described—dividing the lethal dose by the effective dose—fits this concept precisely. Potency refers to how much of a drug is needed to achieve an effect, not how safe that effect is. Half-life concerns how long the drug remains in the body, influencing duration of action. Threshold dose is the minimum amount needed to produce any detectable effect, not the safety margin.

The idea being tested is the safety margin of a drug, captured by the therapeutic index. The therapeutic index is the ratio of the dose that can be lethal to subjects (LD50) to the dose that produces the desired effect (ED50). This shows how much separation there is between effective and toxic doses. A larger therapeutic index means a wider safety margin, so the drug can be used with less risk of toxicity at therapeutic doses. The definition described—dividing the lethal dose by the effective dose—fits this concept precisely.

Potency refers to how much of a drug is needed to achieve an effect, not how safe that effect is. Half-life concerns how long the drug remains in the body, influencing duration of action. Threshold dose is the minimum amount needed to produce any detectable effect, not the safety margin.