Essential Facts about Genetic Testing for Pain Management
The human genome mapping project paved the way to a lab of possibilities. Knowing the genetic code has helped scientist unlock many mysteries about diseases and treatments. One mystery that has always been baffling is when a drug will work for one person but not for another. Sound familiar? Some of you may have been through a cycle of medication trials searching for the one drug that works for you. Instead of feeling like a patient, you might have felt like a lab rat. All those trials and errors left you scratching your ear while wondering whether or not your doctor really knew what he or she was doing. The fact of the matter is that doctors really didn’t know how to predict drug effectiveness or toxicity because everyone is different. But that was then and this is now. Now, doctors do have a test available that helps assess drug responsiveness. Your genes can be a map that serves as a guide for doctors.
_What is Pharmacogenetic Testing (PGT)? _ A simple saliva test is now available that can evaluate your ability to metabolize or process drugs. These drugs like hydrocodone, oxycodone, diazepam, methadone and paroxetine utilize the P450 or UGT systems for metabolism. As a drug gets metabolized, it is broken down into harmless pieces and eventually cleared from your body. The activity of your clearance system is based on your genetic code. Once tested, this knowledge about your drug metabolizing system can guide doctors for the rest of your life.
_What is the purpose of PGT? _ Doctors would like to be able to anticipate how you are going to respond to a drug instead of relying on a trial and error process. By knowing the specific way you break-down drugs, a doctor can tailor your treatment according to your metabolism and immediately find the right drug for you. Not only will this information help doctors predict which drug will best treat your pain, a doctor will also be able to predict your effective dose and potential for toxicity. This knowledge has the potential to save time, money and lives.
_What if someone is an ultra-rapid metabolizer? _ You know who you are. How many times do you need to tell the doctor that the medicine doesn’t work or you need double the dose for it to relieve your pain? Now you don’t have to argue until you’re demonized, you can be tested with PGT to determine once and for all if you really are an ultra-rapid metabolizer.
_What if someone is a poor metabolizer? _ You know who you are. As soon as you take certain medicines you get deathly ill even at very low doses. Instead of going through one medication trial after another only to get sick every time, now your doctor can determine once and for all if you really are a poor metabolizer.
_Are there exceptions? _ Yes, some poor metabolizers will find out that drugs like codeine or tramadol don’t work. And some ultra-rapid metabolizers will find out that drugs like codeine and tramadol make them sick. These drugs are special exceptions because they are "ProDrugs" that have actively potent by-products (metabolites) from being broken-down instead of being broken down into benign waste products immediately. The point is that genetic testing can make this all very clear to your doctor.
_When should you get tested? _
- If you have an unexpected urine drug test results like no parent drug present or unusual levels of a metabolite.
- If you cannot seem to find a drug that works for you
- If you get sick with many types of opioid, benzodiazepine, or antidepressants
_The Bottom Line: _
Pharmacogenetic testing is now available in your doctor’s tool box. Drug responses don’t have to be a mystery any longer now that treatments can be tailored to custom fit you and your genetic code.
Christina Lasich, M.D., wrote about chronic pain and osteoarthritis for HealthCentral. She is physiatrist in Grass Valley, California. She specializes in pain management and spine rehabilitation.