What formula is used to calculate the therapeutic index of a drug?

The therapeutic index is a crucial measure in pharmacology that assesses the safety and efficacy of a drug. It is calculated using the formula TD50 divided by ED50.

In this context, TD50 refers to the dose of a drug that is toxic to 50% of the population, while ED50 represents the effective dose for 50% of the population, showing that it produces the desired therapeutic effect. The therapeutic index provides insight into how safely a drug can be administered; a higher therapeutic index indicates a greater margin of safety because it implies that a significantly larger dose is required to elicit toxic effects compared to the dose needed for effectiveness.

Thus, using TD50 divided by ED50 allows healthcare professionals to assess the safety profile of a medication, determining how far apart the doses for therapeutic effect and toxic effect are, which is essential for safe prescribing and monitoring.