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Overview of Response to Drugs

By

Shalini S. Lynch

, PharmD, University of California San Francisco School of Pharmacy

Last full review/revision Aug 2019| Content last modified Jan 2020
CLICK HERE FOR THE PROFESSONAL VERSION
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Everyone responds to drugs differently. The way a person responds to a drug is affected by many factors, including

Because so many factors affect drug response, doctors must choose a drug appropriate for each person and must adjust the dose carefully. This process is more complex if the person takes other drugs and has other diseases, because drug-drug and drug-disease interactions are possible.

A standard or average dose is determined for every new drug. But the concept of an average dose can be like "one size fits all" in clothing: It may fit a range of people well enough, but it may fit almost no one perfectly. For some drugs, however, the dose does not have to be adjusted, because the same dose works well in virtually everyone.

Effects of age on drug response

Infants and older people particularly have problems with drug response. Their liver and kidneys function less effectively, so drugs that are broken down by the liver or excreted by the kidneys tend to accumulate, thus potentially causing problems.

Older people typically have more disorders than children and younger adults and thus usually take more drugs (see Aging and Drugs Aging and Drugs read more ). The more drugs people take, the more likely they are to have problems caused by one drug interfering with another drug or disease. With aging, people also may have more difficulty following complicated instructions for taking drugs, such as to take the drug at very specific times or to avoid certain foods.

Many Factors Affect Drug Response

Many Factors Affect Drug Response
NOTE: This is the Consumer Version. DOCTORS: CLICK HERE FOR THE PROFESSONAL VERSION
CLICK HERE FOR THE PROFESSONAL VERSION
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