Are your drugs not working? Five ways Pillcheck DNA drug response testing helps

Have you taken a medication that did not seem to work, or that caused side effects other people do not seem to get? Medications are not “one size fits all”. Age, weight, kidney and liver function, other medications and your genes all affect how a drug works in your body. Pharmacogenetic testing, often called PGx, looks at the genes that affect how you break down and respond to medications, so that your prescriber can choose a drug and dose that are more likely to suit you. Here is why medications work differently from person to person, and five ways a Pillcheck test can help.

Why don’t medications work the same for everyone?

Many medications are broken down, or activated, by enzymes in the liver, and the genes for these enzymes vary from person to person. Depending on the versions of a gene you inherited, you may be a poor, intermediate, normal, rapid or ultrarapid metabolizer for a given enzyme. For example:

• Codeine and tramadol must be activated by the CYP2D6 enzyme. Poor metabolizers may get little pain relief, while ultrarapid metabolizers can activate too much, too fast, and have serious side effects.
• The blood thinner clopidogrel, used after a heart attack or stent, must be activated by CYP2C19. In poor and intermediate metabolizers, it may not protect as well, and guidelines recommend an alternative.
• Many antidepressants are broken down by CYP2C19 or CYP2D6. Drug levels can be too high, causing side effects, or too low to work.

These differences are very common. In an analysis of nearly 490,000 people in the UK Biobank, 99.5% carried at least one gene variant that could lead to an atypical response to at least one medication, and about 1 in 4 had already been prescribed such a medication.

Five ways Pillcheck testing helps

1. It covers many commonly prescribed medications

Whether you live with a heart or digestive condition, chronic pain or a mental health condition, or are being treated for cancer, chances are you will need at least one medication affected by your genes. A Pillcheck report covers 355 medications across many treatment areas, which account for over 70% of dispensed prescriptions, so a single test is useful now and in the future. Search the list of medications to see whether the ones you take are included.

2. A pharmacist reviews your results

A genetic result on its own is only part of the picture. A pharmacist trained in pharmacogenetics reviews your results together with your current medications and health history, and prepares written recommendations, such as which medications are likely to work well for you, which may need a different dose, and which are best avoided. You can share these recommendations with your doctor or nurse practitioner, who makes the final prescribing decision.

This approach was evaluated in the ICANPIC study, a Canadian study at two Toronto community pharmacies, where 100 people were tested with Pillcheck. Most were tested because a medication was not working or was causing side effects. Pharmacists identified an average of 1.3 medication problems per person related to the genetic results. Of their recommendations to physicians, 60% were to change the medication, 13% to adjust the dose, 4% to stop a medication and 22% to monitor more closely.

3. It can make your medications safer

The largest study of a multi-gene pharmacogenetic panel, called PREPARE, included 6,944 patients starting a new medication in seven European countries. When prescribing was guided by patients’ genetic results, clinically relevant side effects occurred in 21.5% of patients, compared with 28.6% with standard care, about 30% lower odds of a side effect. The benefit was seen across hospitals, family practices and community pharmacies.

4. It can shorten the trial-and-error process

When a medication does not work, it can take weeks to find out, and switching often means slowly tapering one drug before starting another. This is especially frustrating with antidepressants, which can take several weeks to show their full effect. In a randomized trial in Canadian community pharmacies, people with depression or anxiety whose antidepressant treatment was guided by pharmacogenetic testing improved more over six months than those who received standard treatment. Knowing your results before starting or changing a medication can help your prescriber avoid drugs and doses that are less likely to suit you, so that you have a better chance of feeling well sooner.

5. Your results last a lifetime

Your genes do not change over time, so your Pillcheck results stay accurate and can be used for life, including for medications you may need years from now. As new clinical guidelines and drug labels are published, your report is updated free of charge. You can access your report from your secure account at any time.

What can’t a pharmacogenetic test do?

A pharmacogenetic test does not diagnose disease, and it cannot guarantee that a medication will work. Genes are one of several factors in drug response, along with age, kidney and liver function, other medications, diet, alcohol and how regularly a medication is taken. Results are most useful when a health care professional reviews them together with this information. Do not stop or change a medication on your own based on your results; talk to your prescriber or pharmacist first.

How do I get a Pillcheck test?

Pillcheck uses a simple DNA sample that you collect at home and send to the laboratory (see how to collect your sample). Your results and the pharmacist’s recommendations are available in your secure account, and you can share them with your health care providers.

Pillcheck testing is performed in CAP- and COLA-accredited clinical genetic laboratories located in Canada. Pillcheck reports on 24 genes, increasing coverage with new guidelines and drug labels (see the genes tab), and covers 355 medications, which account for over 70% of dispensed prescriptions. The Pillcheck test panel ensures high accuracy for people of non-European and admixed ancestries. Your results last a lifetime, and report updates are free of charge.

Summary

• Genes affect how your body breaks down and responds to many medications. Almost everyone carries at least one relevant variant.
• A Pillcheck report covers 355 medications, which account for over 70% of dispensed prescriptions.
• A pharmacist reviews your results with your medications and prepares recommendations for your prescriber.
• In the PREPARE study, genetically guided prescribing reduced clinically relevant side effects by about 30%.
• Testing can help your prescriber avoid medications and doses that are less likely to work for you.
• Your results last a lifetime and are updated as new guidelines are published.

Frequently asked questions

Will a genetic test tell me which medication will work?

No test can guarantee that a medication will work. Pharmacogenetic results show how your body is likely to break down or respond to specific medications, which helps your prescriber avoid those that are less likely to suit you and choose a better starting dose.

Should I stop my medication if my results show a gene-drug interaction?

No. Do not stop or change any medication on your own. Share your results with your prescriber or pharmacist, who can decide whether a change is needed.

Is a pharmacogenetic test the same as an ancestry DNA test?

No. Ancestry tests are designed to trace family history. A clinical pharmacogenetic test like Pillcheck is performed in an accredited clinical laboratory, focuses on genes that affect medications, and comes with recommendations based on clinical guidelines.

Do I need to test again if I start a new medication?

No. Your genes do not change, so the same results can be used for new medications throughout your life.

References

McInnes G, Lavertu A, Sangkuhl K, et al. Pharmacogenetics at scale: an analysis of the UK Biobank. Clin Pharmacol Ther. 2021;109(6):1528-1537.

Papastergiou J, Tolios P, Li W, Li J. The Innovative Canadian Pharmacogenomic Screening Initiative in Community Pharmacy (ICANPIC) study. J Am Pharm Assoc. 2017;57(5):624-629.

Swen JJ, van der Wouden CH, Manson LE, et al. A 12-gene pharmacogenetic panel to prevent adverse drug reactions: an open-label, multicentre, controlled, cluster-randomised crossover implementation study. Lancet. 2023;401(10374):347-356.

Papastergiou J, Quilty LC, Li W, et al. Pharmacogenomics guided versus standard antidepressant treatment in a community pharmacy setting: a randomized controlled trial. Clin Transl Sci. 2021;14(4):1359-1368.

Crews KR, Monte AA, Huddart R, et al. Clinical Pharmacogenetics Implementation Consortium Guideline for CYP2D6, OPRM1, and COMT Genotypes and Select Opioid Therapy. Clin Pharmacol Ther. 2021;110(4):888-896.

Lee CR, Luzum JA, Sangkuhl K, et al. Clinical Pharmacogenetics Implementation Consortium Guideline for CYP2C19 Genotype and Clopidogrel Therapy: 2022 Update. Clin Pharmacol Ther. 2022;112(5):959-967.