Prescribing prevalence and trends of medications with pharmacogenetic implications: a study based on primary care data in Manitoba, Canada

To characterize prescribing prevalence and temporal trends of medications with pharmacogenetic (PGx) implications in Manitoba primary care and identify frequently implicated pharmacogenes. We conducted a retrospective, repeated annual analysis of electronic medical record data from the Manitoba Primary Care Research Network (MaPCReN) between 2017 and 2021. Prescribing patterns and unadjusted relative risks (RRs) according to demographic characteristics were assessed. Among 223,630 eligible patients, 42.4% received ≥ 1 medication with PGx implications. Greater exposure was observed among adults aged ≥ 65 years (RR 1.75, 95% CI 1.74–1.77), females (RR 1.24, 95% CI 1.23–1.26), and rural residents (RR 1.23, 95% CI 1.22–1.25) (all p < 0.0001). The aggregate prescribing prevalence of the 10 most common medications with clinically actionable PGx recommendations decreased by 8.0% from 2017 to 2021 (p < 0.001). Pantoprazole (+55.4%) and sertraline (+30.0%) increased, whereas codeine (−33.2%), citalopram (−26.5%), and omeprazole (−20.6%) declined. Frequently implicated pharmacogenes included CYP2D6, CYP2C19, CYP2B6, SLCO1B1, and ABCG2. Medications with PGx implications were commonly prescribed within MaPCReN. These patterns may inform future studies evaluating PGx testing in Manitoba primary care. People can respond differently to the same medication because of differences in their genes. These genetic differences can affect how well a medication works, whether it causes side effects, and what dose may be best for each person. This study examined how often patients receiving primary care were prescribed medications known to be affected by genetic differences in a Manitoba primary care cohort from 2017 to 2021. The goal was to understand whether genetic testing could be helpful in primary care in Manitoba. We found that several commonly used medications may be influenced by genes. This included atorvastatin and rosuvastatin (for cholesterol), amitriptyline, citalopram, sertraline, and venlafaxine (for mental health conditions), codeine (for pain), metoprolol (for heart conditions), and omeprazole and pantoprazole (for acid reflux), which were commonly prescribed and can be influenced by genetics. The key genes involved for these medications are CYP2D6, CYP2C19, CYP2B6, SLCO1B1, and ABCG2. Of 223,630 patients who visited a primary care provider, 42.4% were prescribed at least one medication whose response may be affected by genetic variation. Females and adults aged 19 to 65 were more commonly prescribed these medications. Over time, prescriptions for some medications, such as escitalopram, sertraline, and pantoprazole, increased. These findings show that many patients in the Manitoba primary care cohort were prescribed medications that may be affected by genetic differences. These findings identify a potential opportunity to evaluate how genetic testing could be incorporated into Manitoba primary care to support more personalized medication decisions.