Pharmacogenomics, personalized medicine, and precision dosing: these aren’t just buzzwords anymore.
 
Once a futuristic idea, genetic lab testing is finally here. It is responsive, dynamic, and made easy to use by intelligent software with medication-tracking capabilities.
 
Personalized DNA profiles can be made available to pharmacists, thanks to the GenoScribe pharmacogenetic lab service and comprehensive medication risk management software offered by New Jersey-based Emgenex.
 
I spoke with the company’s vice president of sales, Jaimee Martocci, about how pharmacists can use genetic testing and offer their expertise.
 
Pharmacists are the most-trained health care providers in the study of pharmacokinetics and pharmacology, which includes absorption, distribution, metabolism, and excretion (ADME).
 
Until now, pharmacists’ expertise in ADME has somewhat been kept as pharmacy’s dirty little secret. For some reason, pharmacists have never advertised this knowledge or been able to monetize this important service.
 
Emgenex is changing that, as pharmacists will be able to use GenoScribe to help guide their prescribing practices in a more focused way. Using GenoScribe, “pharmacists can offer specific medication regimen recommendations based on the patient's ability to respond to certain drugs,” Martocci said.
 
Here are a couple of real-life examples of how pharmacists can intervene and help patients avoid common adverse drug events through genetic testing:
 
Patient A  
A 58-year-old male has his first myocardial infarction. He gets a stent placed, the cardiologist puts him on clopidogrel (Plavix), and he goes home thinking the medication will prevent another episode.
 
If that patient is a poor metabolizer of cytochrome P450 2C19 (CYP2C19), however, then he may not respond fully to the platelet inhibiting effects of clopidogrel, and he will therefore be at higher risk for another heart attack or stroke.
 
Pharmacists know that clopidogrel requires activation by CYP2C19 because it is a prodrug. A prodrug is developed in order to improve absorption in the body, distribution into the various tissues, metabolism by CYP enzymes, and excretion from the body. Genetic testing can help identify patients who are unable to convert prodrugs into their active therapeutic forms.
 
A simple genetic test is all that is needed to determine if the patient’s liver produces enough enzyme to activate clopidogrel to its full anti-clotting potential. If the pharmacist is able to check the new prescription from the cardiologist against the patient’s DNA profile, then he or she would be able to recommend the use of an alternate therapeutic option such as prasugrel (Effient) or ticagrelor (Brilinta).
 
What are a patient’s odds of being a poor metabolizer of CYP2C19?
 
The variant allele CYP2C19*2 is a gene variant that renders the CYP2C19 much less effective at its job. It is estimated that at least 1 copy of the CYP2C19*2 variant allele is present in 25% of white, 30% of black, and 40% to 50% of Asian patients.1
 
If that isn’t alarming enough, then let's look at another possible case. An estimated 22 million to 25 million women take selective serotonin reuptake inhibitor (SSRIs) in the United States, and CYP2C19 is one of the major metabolic pathways for citalopram, sertraline, fluoxetine, venlafaxine, and moclobemide.2
 
Patient B  
A 40-year-old female is experiencing moderate anxiety and depression. Her primary care physician (PCP) starts her on citalopram 20 mg for 2 weeks, and then increases the dose to 40 mg thereafter.
 
The patient fills the prescription and begins taking the medication. After 4 weeks of use, the patient begins feeling worse and worse.
 
She is having dizzy spells and some heart palpitations. When she returns to the PCP, she is told that she’s having spells of tachycardia with QT prolongation.
 
The PCP calls the pharmacy and asks if the pharmacist has ever heard of citalopram causing this problem. The pharmacist informs the prescriber that the patient may be a poor metabolizer of CYP2C19 and she would require at least a 50% dose reduction in citalopram.
 
Genetic testing not only helps avoid “trial and error” prescribing, but it can also guide therapy when the stakes are even higher. Breast, colon, and non-small cell lung cancers can be combatted more effectively and efficiently.
 
According to the literature, “physicians who are early adopters of safe and effective medical technologies enjoy improved clinical performance, greater patient satisfaction and lower liability risk.”3  
 
Pharmacists can help ease the transition from “defensive medicine” to proactive medicine by helping physicians become early adopters of this new pharmacogenomics testing technology.
 
Point-of-care DNA testing can be easily added to a pharmacy’s spectrum of clinical service offerings. When pharmacists can combine medication therapy management with the power of personalized genetic testing, they can provide excellent patient care.
 
If you want more information on how you can add DNA testing to your pharmacy or as part of your independent consulting services, contact Dr. Thielemier at blairthielemier@btpharmacyconsulting.com to find out how you can begin offering pharmacogenomics testing services!
 
References
1. Scott SA, et al. PharmGKB summary: very important pharmacogene information for cytochrome P450, family 2, subfamily C, polypeptide 19. Pharmacogenet Genomics. 2012;22(2):159–165.
2. Antidepressant Use in Persons Aged 12 and Over: United States, 2005–2008. US Centers for Disease Control and Prevention. http://www.cdc.gov/nchs/data/databriefs/ db76.pdf.
3. Kessler D. Do doctors practice defensive medicine? Quart. J. Economics. 1996;111(2):353–390.