Personal Genetics and Prescription Drugs

By Amy Cowen on May 9, 2012 5:58 AM

A single DNA mutation you don't even know you have may determine whether or not the medication your doctor prescribed will work for you.

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Due to differences in individual genetic makeup, prescription medications may work differently for different people. Online pharmacogenomics databases help document the relationship between genetic mutation and pharmaceuticals.

When you catch a cold, you might reach for an over-the-counter product to help relieve symptoms like nasal congestion, itchy eyes, or a sore throat. If your symptoms are more severe, you may end up at the doctor and go home with a prescription for a stronger medication. According to a U.S. Centers for Disease Control and Prevention study between 2007 and 2008, almost half the U.S. population had taken at least one prescription drug in the month prior to being surveyed. That approximately 48% of the U.S. had "recently" used a prescription medication is an eye-opening statistic. Even keeping in mind that many prescriptions are prescribed to treat a specific, short-term condition, the numbers indicate that there are a lot of pills being counted out and swallowed each day to treat and safeguard against a variety of illnesses and health problems.

No Guarantees

Pharmacies often provide counseling, warnings, and helpful information about various potential side effects of specific medications. Patients who take more than one medication are also alerted when a possible problem exists between medications, and they should not be taken together. Patients are also routinely counseled to be sure and finish the prescribed course of medication, even if they start to feel better before they run out of the medicine. This is particularly true with antibiotics. Taking the complete course of an antibiotic helps reduce the risk of new and drug-resistant forms of bacteria developing. But even if you take only one medication, take it completely, and follow all the directions, the prescription drug you take home from the pharmacy may not work for you the way the pharmaceutical company claims it will or the way your doctor expects.

Pharmaceutical companies develop drugs to treat specific conditions. For example, Atorvastatin is used to help lower cholesterol, and Clopidogrel helps prevent blood clots. Based on extensive testing and research, drugs like these are marketed and prescribed for patients. While generalizations can be drawn about the application and effectiveness of a medication, the reality is that there will likely be exceptions. Maybe you've noticed that when you pick up a medication at the pharmacy that there is typically a sheet containing a list of possible side effects and warning signs. Similarly, when you see a commercial on television for a drug, there is always a bunch of really fast talk at the end (often accompanied by some 'fine print' on the screen) that makes clear that things can go wrong. Sometimes it seems that this laundry list of possible complications includes almost every possible symptom one can imagine. The warnings can be frightening, and it's clear that drug companies can't guarantee that their medication will work for you—or won't cause a problem.

So what's going on? Why are there so many precautions and discussions of side effects? If a pill is supposed to cure problem X, Y, or Z, can't you simply swallow it with a cup of water and let the pill do its work?

Medications and Your Genes

How your body responds to a particular drug may depend on your genes. In other words, something in your DNA may make you more or less responsive to a drug and more or less likely to have an adverse or atypical reaction. Your personal genome contains 20,000 to 25,000 genes, and each of those genes contains hundreds to millions of DNA nucleotides. When you do the math—20,000 genes multiplied by x nucleotides—it is not hard to imagine that there is plenty of room for anomaly or mutation within a single person's genome. It might be easy to think that with all those nucleotides at work, one mutation won't really make a difference. But, in fact, a single change in DNA sequence may affect the way a specific prescription drug will work for you.

Making Connections

The study of the relationship between genetics and the biological interactions stimulated by prescription medications is called pharmacogenomics. In the "Drugs & Genetics: Why Do Some People Respond to Drugs Differently than Others?" project, students can learn more about the connections between certain kinds of mutations called single-nucleotide polymorphisms (SNPs), biological signaling pathways, the cellular proteins with which a drug might interact, and the effectiveness of a drug. In this Project Idea from the Medical Biotechnology interest area, students choose a drug of interest and then use an online pharmacogenomics database to investigate the ways in which genetic mutations interfere, specifically, with the function of that drug.

Project Ideas in Medical Biotechnology are sponsored by support from the Amgen Foundation.