What term best describes the ratio between the toxic and therapeutic effects of a drug?

The term that best describes the ratio between the toxic and therapeutic effects of a drug is known as the therapeutic index. This measure is crucial when assessing the safety and efficacy of medications. The therapeutic index provides a quantitative way to evaluate how much of a drug is needed to produce the desired therapeutic effect compared to the dosage that might cause adverse effects or toxicity. A high therapeutic index indicates that a drug has a wide margin of safety, meaning there is a substantial difference between the effective dose and the toxic dose. This distinction is vital for clinicians in prescribing medications, as it helps them determine appropriate dosages while minimizing the risk of harmful side effects.

The other options refer to different concepts. The effective dose pertains to the amount of a drug required to achieve a certain level of effect in a specified percentage of the population, while the safety profile encompasses a broader view of the risks and benefits associated with a drug, including side effects and contraindications, rather than strictly the ratio of toxic to therapeutic dosages. Potency index is not a commonly used term in pharmacology and does not directly relate to the comparison of toxic and therapeutic effects like the therapeutic index does.