Comprehensive Nursing Pharmacology Q 281
Safety of a drug is determined by the degree between:
A. Therapeutic and toxic doses.
B. Potency and efficacy.
C. Subtherapeutic and toxic levels.
D. Side and adverse effects.
Correct Answer: A. Therapeutic and toxic doses.
Safety is determined by the degree between therapeutic and toxic doses. The Therapeutic Index ( TI ) is used to compare the therapeutically effective dose to the toxic dose of a pharmaceutical agent. The TI is a statement of relative safety of a drug. It is the ratio of the dose that produces toxicity to the dose needed to produce the desired therapeutic response.
Option B: Potency and efficacy are not related to safety. Potency denotes the amount of drug needed to produce a given effect. Efficacy is the maximal effect that a drug produces irrespective of concentration (dose) Potency: We generally refer to potency as the amount of drug dose that produces a quantal effect in 50% of the population.
Option C: Subtherapeutic levels are not part of safety determinations because if a drug is subtherapeutic it does not exert any desired effect. Toxicity can be measured by the effect the substance has on an organism, a tissue, or a cell. We know that individuals will respond differently to the same dose of a substance because of a number of factors including their gender, age, and body weight. Therefore a population-level measure of toxicity is often used.
Option D: Side effects are expected, and adverse effects are often the result of toxicity. A side effect is an undesirable physical symptom caused by taking a drug or undergoing medical treatment or therapy. Side effects can range from relatively minor symptoms—such as drowsiness or an upset stomach—to serious effects such as liver damage, and sometimes even life-threatening or potentially fatal effects.