Many drugs are known to metabolize poorly in people with certain genetic variations. Specifically, more than 250 of the most commonly prescribed medications that are used to treat a variety of conditions, are recognized by the FDA as being susceptible to genetic-driven impacts.  And, we know that nearly 90% of the population has at least one genetic variation that may affect their response to medications.
When you take a drug or are exposed to an environmental toxin, enzymes in your body get to work to break down that drug so it can be excreted.
Your specific genetic makeup determines how these enzymes work to break down drugs.
Differences in how enzymes break down drugs can mean that people need different doses of a particular drug to achieve the same effect, or that some drugs might not be as effective for them. Many of these gene variations are very common in the general population and can affect decisions about the right drug or right drug dose.
Thousands of medications are affected by genetics — not all drugs provide the same results, and by understanding genetics, we can better understand what medication may work before you take it. Over 250 of the most commonly prescribed medications are so susceptible to these genetic-driven impacts that the FDA has issued a warning/guidance on their medication labels.
Tamoxifen is a medication for the treatment of breast cancer or for people at a high risk of developing breast cancer.