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Adverse drug reactions, or ADRs, are harmful side effects of medications. Studies have shown anywhere from five to thirty percent of patients experience some form of adverse drug reaction. Common manifestations of ADRs include rashes, hives, itching, fever, swelling, and shortness of breath. While many ADRs are merely annoyances, some can be much more serious. Adverse drug reactions are responsible for 6% of hospital admissions, and cause more than 100,000 deaths per year.

Naturally, the ability to predict and avoid adverse drug reactions is one of the biggest advantages pharmacogenomics offers. Such knowledge could save lives, as well as sparing both patients and doctors much time, money, and trouble. Even in cases where the side effects of a medicine must be accepted for the sake of the patient’s overall health, knowing what side effects to expect before beginning a treatment offers a great advantage.

ADRs can be caused by either the immune system or various nonimmune sources. Nonimmune drug reactions include pseudoallergic reactions, drug intolerances, overdoses, and interactions between multiple drugs. But the majority of ADRs stem from the immune system, and are caused by an interaction between compounds in a given drug and major histocompatibility (MHC) molecules, in the patient, resulting in an allergic reaction. It’s these immune responses that pharmacogenomics is working to predict.

Today, there are genetic tests, that can determine how patients will respond to certain drugs. Markers for ADRs can be found even in small blood or saliva samples, so some tests are even simple enough to be done at home, using a testing kit. These tests are especially helpful to patients with chronic conditions who have experienced ADRs in the past, or who are having trouble finding a drug that works for them.

Currently, the biggest successes in pharmacogenomics have been made by those studying the effects that genetics have on heart medications, pain relief medications, and antidepressants. I’ve talked more in depth on pharmacogenomics’s findings on chronic pain and depression in previous entries on this blog.

Even though we’ve known about genes for a long time, we’ve only just begun to understand the complexities of our genetics. But our growing awareness of how genes affect our responses to drugs has already significantly improved the quality of medical care doctors can provide, and in the case of ADR prediction, helped patients avoid some seriously dangerous reactions to drugs.