We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.
Medicine

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

What Is the Therapeutic Ratio?

Mary McMahon
By
Updated: May 17, 2024
Views: 3,889
Share

The therapeutic ratio expresses the relationship between a medication’s effectiveness and its toxicity. It is also called the therapeutic index. Researchers determine this value in clinical trials and other studies by determining the dosage at which the medication becomes toxic, and dividing by the effective dosage. These studies rely on doses that perform that way in at least 50% of the study population. The higher the therapeutic ratio, the more of a medication a patient would need to take to develop toxic symptoms.

Care providers want to treat disease in patients while limiting side effects. The therapeutic ratio provides important information about how a medication performs in most patients, which a doctor can use to decide on the best course of treatment for a given patient. This can be especially important in the case of drugs with a Narrow Therapeutic Index (NTI), where the difference between a beneficial and toxic dose can be very slight.

A common example comes up in radiation therapy. This treatment is used for cancers and certain other conditions. The radiologist wants to kill the cancer cells and stop their growth, but must consider damage to the neighboring tissue in the process. Blasting a tumor with a very high dose of radiation could be dangerous for the patient. Instead, the radiologist considers the effective dose for the cancer, based on the type of tumor and location in the body, and takes care to avoid entering the danger zone where neighboring tissue would be destroyed.

Some toxicity may be considered an acceptable outcome with treatment because it may be necessary to resolve the problem. In radiation, for instance, it is impossible to treat a cancer without damaging some neighboring cells. Using the therapeutic ratio, care providers can determine the probability of toxicity in a patient’s case and weigh it against the benefits. In NTI drugs, it is also very important to calculate dosing correctly and warn patients. Taking two pills instead of one by accident, for example, could have serious consequences.

Lethality studies are not performed in human populations, for ethical reasons; killing patients in a clinical trial to find out how much medication constitutes a fatal dose would be frowned upon. Instead, researchers rely on toxicity reported in such studies, including side effects and serious complications. These can vary considerably depending on metabolism and other factors, which is why some patients experience serious complications at seemingly safe dosages, while others can overdose without long-term ill effects. The therapeutic ratio reflects the median range.

Share
WiseGeek is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Mary McMahon
By Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a WiseGeek researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Editors' Picks

Discussion Comments
Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a...

Learn more
Share
https://www.wisegeek.net/what-is-the-therapeutic-ratio.htm
Copy this link
WiseGeek, in your inbox

Our latest articles, guides, and more, delivered daily.

WiseGeek, in your inbox

Our latest articles, guides, and more, delivered daily.