Pharmacogenomics is the term doctors use to discuss how a person’s DNA affects drug metabolism. Prior to the understanding of DNA, doctors knew that certain races could have different responses to drugs. An example is a common blood thinner called Plavix. Doctors stopped prescribing this medication to Asians or Pacific Islanders because 50% of them had a poor response to the medication. Now we know the exact gene that is behind this response, and often a specialist will order the genetic test if the medication is important.
Most insurance companies and doctors are slow to adopt scientific knowledge that pharmacogenomics provide. Instead, they rely on side effects or allergic reactions before changing a medication. In adults over 65, more than 40% take five or more medications per day and 71% are on a statin medication. Statins inhibit an enzyme in the liver to be effective. There are common gene variants that are responsible for statin breakdown. For example, a single gene variant, SLCO1B1*5, prevents a liver transporter to take up the statin and therefore the liver has less chance to metabolize it or break it down. Therefore patients with this variant develop high levels of the statins in the blood, which often lead to muscle breakdown, and most definitely severe mitochondrial dysfunction. The other well-known gene variant is the CYP3A4*22 gene, which is responsible for metabolizing statins in the liver. A person with this gene variant in less able to covert the statin to an inactive metabolite causing higher statin levels in the blood which can lead to severe muscle breakdown and kidney injury.
Pharmacogenomic testing can mitigate risk by aiding a clinician to pick a compatible drug that is best tolerated by the patient. Medicine based on an individual’s genomics is referred to as Precision Medicine. In 2015, only 25% of doctors had any formal training in genetics. Genetics education requires a firm understanding of biochemistry and molecular biology. As we move into the future of genetics and precision medicine, doctors are hit with all sorts of barriers to learning and adopting the necessary new practices. One study found that many doctors have minimal science training and most insurance reimbursements will only pay for the typical 15-minute visit. Thus, most doctors report they feel ill prepared to integrate genomics into their practice.
The most amazing component of pharmacogenomics is its ability to push medicine away from a reactive approach or the one size fits the entire population approach, towards a personalized proactive precision approach. But how long will it take conventional medicine to own their limitations? For now, in my world of Precision Medicine, we change lives ‘One GENE at A TIME’.
