Drug-Gene Testing: Can These Tests Help Determine the Best Medications for Patients?

A drug-gene interaction refers to how someone’s genes affect the way that they will react to a certain medication—will the medication work? Will it produce negative side effects? Many patients respond differently to the same medication. This creates a challenge for both doctors and pharmacists. 

Pharmacogenetics, also called pharmacogenomics, is the study of how a person’s genes can affect the way that their body responds to medications. Pharmacogenetics can help doctors and pharmacists create a medication regimen that meets the specific needs of each patient.  

How Do Someone’s Genes Affect How Their Body Responds to Medicine?

There are thousands of genes in the body. Genes carry information that tells the body how to make proteins that determine our traits, like eye color, blood type, and even how the body reacts to medications. Different people have different versions of the same genes. Each variation of a gene carries instructions to make a different type of protein, and therefore create different traits. This is why some people have blue eyes, while others have brown or green eyes. 

Genetic variations also determine how a person’s body processes medications. For example, the CYP2D6 gene produces an enzyme (a type of protein) called the CYP2D6 enzyme that processes painkillers in the liver. People who have a genetic variation of the CYP2D6 gene that makes the body produce a higher amount than normal of the CYP2D6 enzyme can process painkillers more quickly than those who make less. If a prescription painkiller is processed too fast by the body, it can potentially cause an overdose. Pharmacogenetics can help doctors understand what dose of painkillers works best for certain patients. For example, a doctor may prescribe a lower dose of painkiller for a patient who produces a lot of the CYP2D6 enzyme.

In the case of antidepressants, approximately one-third of patients do not find relief from depressive symptoms even after trying multiple antidepressants—this is referred to as treatment-resistant depression. More than half of all patients who take antidepressants report experiencing side effects, like dry mouth, headache, and decreased sex drive. Scientists are currently using pharmacogenetics to understand why some people do not respond to certain antidepressants and why some people experience side effects, while others don’t. 

Understanding Drug-Gene Interactions Helps Doctors and Pharmacists Provide Personalized Medication Regimens

The ultimate goal of medication therapy is to safely and effectively treat a patient with the correct medication, at the right dose, and at the right intervals, with the least amount of side effects. Doctors consider many factors when creating medication regiments, like age and medical history. Now, doctors can consider genetics. 

Should Everyone Get Drug-Gene Testing?

In some cases, drug-gene testing can be very valuable. When a drug-gene interaction is well established, drug-gene testing can help protect someone from life-threatening side effects. But not all drug-gene interactions are life-threatening, and genetic variations aren’t the only factor that affects how the body processes medications.

Many factors influence how a persons’ body processes medications, like diet, age, gender, and whether or not the individual is a smoker. Although drug-gene testing can be very informative in certain situations, placing too much attention on drug-gene interaction can, in some cases, cause more harm than good. For example, some patients report feeling anxious or scared about taking certain medications after receiving results from a drug-gene test, even when they know that the medication is necessary for treating their condition. 

Where Can I Get Drug-Gene Testing?

Your doctor may recommend drug-gene testing if he/she is prescribing you a medication with a known drug-gene interaction, for example, medication for heart disease or irritable bowel syndrome. Some companies advertise at-home drug-gene testing kits, but patients should not make any changes to their medications before talking with their doctor.