How Our Genes Influence the Way We Respond to Medications

People can take the same medication at the same dose and have very different experiences. One person may improve quickly, another may develop side effects, and someone else may notice very little benefit.

One reason is that our genes are different.

Genes are like instructions that help guide how our bodies work. Some of these instructions affect how medications are:

• absorbed,
• processed,
• carried through the body,
• broken down,
• and used by the brain and other organs. Because these instructions vary from person to person, the same medication may not behave exactly the same way in everyone.

For example, one person may break down a medication very quickly. The medication may leave their body before it has enough time to work properly. Another person may break down the same medication more slowly, causing higher levels to remain in the body and increasing the chance of side effects.

Genes can also influence how sensitive we are to a medication once it reaches its target.

Medications often work by interacting with specific parts of the body or brain. Genetic differences can affect how these targets function. This means that even when two people have similar amounts of a medication in their bodies, one may respond very well while the other may respond poorly.

A simple way to think about it is:

1. Your genes
2. Influence how your body handles a medication

and

1. Influence how your body responds to that medication
2. The same medication can work differently for different people

This is one of the reasons prescribing medication can sometimes involve trial and error.

Pharmacogenomic testing, or PGx testing, looks at genetic differences that may affect medication response. The information can help healthcare professionals better understand whether a medication may be processed normally, whether a different dose may be worth considering, or whether another medication may be a better fit.

PGx testing cannot guarantee that a medication will work, because many other factors also influence treatment. But it can provide another piece of information to help make medication choices more personalized to the individual.