Therapeutic index

Therapeutic Index

The Therapeutic Index (pronounced: thuh-ruh-pyoo-tik in-deks), also known as Therapeutic Ratio, is a comparison of the amount of a therapeutic agent that causes the therapeutic effect to the amount that causes toxicity. The therapeutic index is used to assess the safety of a drug.

Etymology

The term "Therapeutic Index" is derived from the Greek word "therapeia" meaning healing and the Latin word "index" meaning pointer or indicator.

Definition

The Therapeutic Index is defined as the ratio of the toxic dose to the therapeutic dose of a drug, which is used to measure the relative safety of the drug for a particular treatment. It is a measure of the drug's safety margin, and is calculated as the lethal or toxic dose (TD50) divided by the effective dose (ED50).

Calculation

The Therapeutic Index is calculated using the formula:

Therapeutic Index = TD50 / ED50

Where:

• TD50 (Toxic Dose) is the dose of a drug that is toxic to 50% of the population.
• ED50 (Effective Dose) is the dose of a drug that is therapeutically effective in 50% of the population.

Related Terms

• Pharmacodynamics
• Pharmacokinetics
• Toxicology
• Drug Safety
• Drug Efficacy

See Also

• Drug Discovery
• Clinical Trials
• Pharmaceutical Industry

References

• Goodman & Gilman's The Pharmacological Basis of Therapeutics, 12th Edition.
• Rang & Dale's Pharmacology, 8th Edition.

External links

• Medical encyclopedia article on Therapeutic index
• Wikipedia's article - Therapeutic index

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