1. What is Therapeutic Index?

Definition: The Therapeutic Index (TI) is a quantitative measurement of the safety of a drug that compares the toxic dose to the effective dose.

Purpose: It helps healthcare professionals assess the relative safety of medications and make informed dosing decisions.

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 there's a wider margin between effective and toxic doses.

3. Importance of Therapeutic Index

Details: Drugs with low TI require careful monitoring (e.g., digoxin, warfarin), while high TI drugs (e.g., penicillin) are generally safer.

4. Using the Calculator

Tips: Enter the TD₅₀ (toxic dose) and ED₅₀ (effective dose) in mg. Both values must be > 0 (ED₅₀ 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 indicates a narrow therapeutic window requiring close monitoring.

Q2: How is TD₅₀ determined?
A: TD₅₀ is typically established through animal studies and clinical trials, measuring the dose that causes toxicity in 50% of subjects.

Q3: What factors can affect therapeutic index?
A: Age, weight, genetics, drug interactions, and organ function can all influence a drug's effective and toxic doses.

Q4: Is therapeutic index the same as therapeutic window?
A: No, therapeutic window refers to the range between minimum effective concentration and maximum safe concentration in plasma.

Q5: Why is this important for nurses?
A: Understanding TI helps nurses monitor for adverse effects, recognize high-risk medications, and educate patients about their medications.