1. What is Therapeutic Index?

Definition: The therapeutic index (TI) is a quantitative measurement of the safety of a drug that compares the dose that causes toxicity to the dose needed for therapeutic effect.

Purpose: It helps healthcare professionals assess the relative safety of medications and determine appropriate dosing ranges.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( TI \) — Therapeutic Index (dimensionless)
• \( TD_{50} \) — Toxic dose for 50% of the population (mg)
• \( ED_{50} \) — Effective dose for 50% of the population (mg)

Explanation: A higher TI indicates a safer drug, as the toxic dose is much higher than the effective dose.

3. Importance of Therapeutic Index

Details: Drugs with a low TI require careful dose monitoring, while those with high TI can be prescribed with less concern about toxicity.

4. Using the Calculator

Tips: Enter the TD₅₀ (toxic dose) and ED₅₀ (effective dose) in the same units (typically mg). Both values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is considered a good therapeutic index?
A: Generally, a TI > 10 is considered safe, while < 3 is considered potentially dangerous.

Q2: How is TD₅₀ determined?
A: Through preclinical and clinical trials observing toxic effects in test populations.

Q3: How is ED₅₀ determined?
A: Through dose-response studies measuring the drug's effectiveness in test populations.

Q4: Can TI be used for all drugs?
A: TI is most useful for drugs with dose-dependent toxicity. It's less meaningful for drugs with idiosyncratic reactions.

Q5: What are limitations of therapeutic index?
A: TI doesn't account for individual variations, drug interactions, or non-dose-dependent adverse effects.