Pharmacogenetics: Genetic Testing for Personalized Medical Treatment
The more we learn about genetics, the better able we are to impact a myriad of health conditions through personalized medical treatment. The unique tailoring of customized therapies to a person’s own genetic profile enables improved outcomes with a reduced need for trial and error. If we can know in advance how a particular medication will work for each individual, we can alter the treatment or dosage prescribed to meet the patient’s needs. This is no longer the science fiction depicted in movies and television, but a reality that is beginning to play out in medical centers and hospitals across the country – and with the potential for improved levels of care for children.
This new field – pharmacogenetics – is the study of how a person’s genes affect the response to various medications. DNA will show how each individual metabolizes drugs to provide a custom-tailored approach to treating a condition. Knowing how a drug will be absorbed and metabolized can eliminate the lengthy time it takes to find the right treatment for each person.
One of the best aspects of this testing is that it does not require a needle to draw blood. A quick swap of the inside of the cheek is all that is needed to make this determination. This is especially useful for children who often have a fear of needles. Since the liver plays a role in the metabolization of many medications, being able to avoid adverse liver reactions is one more positive aspect associated with this testing.
Pharmacogenetics looks at genes for variances in proteins that affect medication responses. This can include liver enzymes responsible for converting drugs into their active or inactive forms. A small difference in a genetic sequence can impact how a medication performs or whether there will be adverse reactions. The liver enzyme CYP2D6 is a prime example for this scenario as it acts on one-fourth of all prescription medications. Most people have two copies of each gene, but some have hundreds or thousands of copies of CYP2D6. This can result in the rapid metabolization of a drug. For example, CYP2D6 converts the painkiller codeine into morphine, and a person with extra copies will convert codeine to morphine at such a rapid rate that even a standard dose can result in an overdose of medication.
Potential Areas for Pharmacogenetics
Pharmacogenetics is currently in use for children with leukemia for better dosage control. Adults taking Plavix to prevent blood clots after heart attacks are beneficiaries of these genetic test results since discovering that roughly 30 percent of adults receiving this medication cannot fully convert it in their bodies rendering it a less effective option for the prevention of strokes and heart attacks in the future.
Treatment for ADHD in children is often hit or miss. What works for one child will not bring the same results for another. Side effects such as drowsiness, weakness in the legs, mood swings, stomach pain, loss of appetite, and delayed growth could be avoided if pharmacogenetics can help predict a better choice of medication at the start of treatment.
One mother, who asked not to be named for her son’s privacy, reported a positive experience with genetic testing. Her son, who has both autism and major depression disorder with anxiety, had experienced terrible side effects when taking Paxil. After swabbing each side of the mouth, the results came in within a week.
Her son’s doctor explained that there would be three categories regarding potential medications:
- First category – a group of medications that match the gene type or chemistry
- Second category – drugs that could be effective without too many bad side effects
- Third category – medications that should not be used because of gene interaction (as it turned out, Paxil fell into this category for her son)
Two weeks into the new medication (Wellbutrin – a category one drug for her son) and there have been no bad side effects, he is sleeping well, and there have been no changes in appetite.
Some of these medications can be addictive, as well. Because drug dosages are not always researched for children in medical studies, doctors are at the mercy of limited knowledge during diagnostic stages. This is where genetic testing can eliminate the trial and error and provide a quick determination of what medication will work the best for the child.
One area where personalized medicine based on genetic testing is helpful is depression. Patients who are either considering the use of antidepressants or have not seen the desired results from previous treatment for this condition now have the opportunity to discover – through a simple cheek swab – what medication will work the best and which ones should be avoided based on the potential for adverse reactions or lack of benefits.
Other current uses for pharmacogenetics are HIV, breast cancer, and colon cancer, with bloodthinning, mental health, autism, and asthma studies also underway. In regards to autism, current research has shown promising results and significant progress towards the pharmacogenomics of autism, with additional validation needed by further studies. An upcoming study in conjunction with Sanofi will evaluate the use of Lixisenatide (a medication that may improve glucose control in adults with type 2 diabetes) in acute coronary syndrome. Another hope is that pharmacogenetics will help improve future laboratory drug research and development.
At this time, more than 150 medications have pharmacogenetics information on their labels from the FDA. This provides genetic-specific dosing and other factors that can help doctors find the best medication for each person.
How Do You Metabolize Medications?
Most people are unaware that roughly 2 million hospitalizations resulting from adverse reactions to medications occur each year. Just imagine how much of this could be avoided by treatments that are custom tailored to each person’s genetic make-up. The genes we carry in our bodies do more than determine body shape, blood type, hair color, eye color, and other characteristics – they also regulate how the body will process medications. For example, take a look at the following categories of how people metabolize medications:
Ultrarapid Metabolizer (UM) – people in this category process medication at a very quick pace, often metabolizing it before its therapeutic effects can have an impact on the body. Drug treatments are often seen as ineffective with little to no relief as an outcome.
Extensive Metabolizer (EM) – the people in this group often see the best results because they absorb the medication effectively with little to no side effects. They experience relief from their symptoms – often at the fastest possible rate.
Intermediate Metabolizer (IM) – this individual metabolizes medication at a slower than normal rate. There is a higher chance of mild toxicity and side effects for these people. Outcomes from treatment here is hit or miss, with the potential for some symptom relief, although not as much as desired in most cases.
Poor Metabolizer (PM) – this is the category that you do not want to be in as the body process medication at a very slow rate. This means the bloodstream contains higher quantities of the medicine for longer periods, increasing the risk of side effects and even life-threatening conditions.
Why Is Pharmacogenetics Use Not Widespread?
You would think that something that could predict how a person will handle a medication would be widespread in use, but that is not the case. Because this is a newer method of testing, many doctors do not yet know it exists. Since most insurers do not yet cover genetic testing for the purpose of determining medications, doctors rarely prescribe the process. Instead, patients are often guinea pigs waiting and watching through trial and error after one medication after another fails to yield positive results.
Doctors and insurance companies tend to wait until all of the verdicts are in before approving and embracing new technology. At this time, the experts still disagree on the benefits of pharmacogenetics. While it has worked wonders for some people – zeroing in on treatments that will be both safe and effective, it has had the opposite effect for other individuals. For some people, medications have been recommended that have already been tried with bad reactions. The science is not yet perfect enough in all areas. There are also no genetic markers at this time for autism and ADHD, making it impossible to get complete readings for potential treatments for everyone with these conditions.
Does that mean you should forgo looking for options for genetic testing for drug therapy? The only person who can make that decision is you – with the help of a knowledgeable doctor in the field of pharmacogenetic testing. Clearly, if your child is currently receiving treatment that works – without any side effects – you may not want to pursue this avenue since there is a strong chance you will have to pay out of pocket for the test if it is not covered by your insurance company. However, if you are not happy with the current treatment your child is receiving, genetic testing may be the best option at this time.