In healthcare, patient safety is paramount. Yet, despite advancements in medicine, adverse drug reactions (ADRs) continue to be a major concern, affecting patients globally. In Canada alone, there are an estimated 200,000 ADRs annually that result in hospital admissions and cause tens of thousands of deaths. These reactions underscore the need for safer, more personalized approaches to prescribing medications. One such approach is pharmacogenetics (PGx), a field that examines how an individual’s genetic makeup influences their response to medications.

By utilizing pharmacogenetic testing before starting any medication, healthcare providers can better predict how a patient might metabolize a drug, thus enhancing health outcomes. In this article, we discuss how this proactive approach offers a pathway to personalized treatment plans that not only improve efficacy but also minimize the risk of harmful side effects to improve patient safety.

The Scope of Adverse Drug Reactions

ADRs are a growing public health issue. According to the World Health Organization (WHO), ADRs are the most common cause of hospital admission and the fourth or sixth leading cause of deaths worldwide. In Canada, each year, adverse drug reactions are responsible for  killing between 10,000 to 22,000 Canadians, and costing the Canadian healthcare system between $13.7 and $17.7 billion (Adverse Drug Reaction (ADR) Canada). These figures highlight the need for innovative strategies like pharmacogenetics to enhance drug safety.

A common cause of ADRs is variability in how individuals metabolize medications. For example, some people are "poor metabolizers," meaning they process certain drugs more slowly, leading to a buildup of the drug in their system, which increases the risk of toxicity. On the other hand, "ultra-rapid metabolizers" process medications too quickly, rendering standard doses ineffective.

How Pharmacogenetics Enhances Patient Safety

Pharmacogenetic testing identifies genetic variations that influence how a patient metabolizes drugs, enabling healthcare providers to prescribe the right medication at the right dose from the outset. This personalized approach dramatically reduces the trial-and-error period often associated with finding the correct medication, which is a frequent cause of ADRs. 

Pharmacogenetics for Pain Management Medications 

A key example is the role of pharmacogenetics in opioid prescriptions. Opioids are commonly prescribed for pain management, but their efficacy and risk of addiction vary among individuals due to genetic differences. For instance, genetic variants in the CYP2D6 enzyme affect how patients metabolize opioids like codeine. Research shows that 5%-10% of Caucasians are poor metabolizers of codeine, meaning they receive little to no pain relief from the drug, while 1%-2% are ultra-rapid metabolizers, putting them at increased risk of opioid toxicity(Dean, 2012). By identifying these genetic variations before prescribing opioids, doctors can tailor treatment to minimize harm and maximize effectiveness.

Pharmacogenetics in Mental Health Medications

Beyond pain management, pharmacogenetics is crucial in mental health treatment. Many patients experience ADRs or poor efficacy when starting antidepressants, partly because genetic factors influence how these drugs are metabolized. Studies show that up to 55%-60% of patients with depression do not recover fully on an antidepressant medication (Al-Harbi KS). Genetic testing can reveal variations in enzymes like CYP2C19 and CYP2D6, which metabolize common antidepressants such as selective serotonin reuptake inhibitors (SSRIs). With this information, clinicians can adjust dosages or select alternative medications, reducing the risk of adverse reactions and improving treatment outcomes.

Reducing Medication Errors

Pharmacogenetic testing not only prevents ADRs but also reduces medication errors. According to a report by the Institute of Medicine, medication errors are responsible for at least 1.5 million preventable adverse drug events in the United States each year. Many of these errors result from the failure to consider individual differences in drug metabolism. By utilizing pharmacogenetic data, healthcare providers can better predict drug responses, thus reducing the likelihood of both under- and overdosing.

Encouraging Proactive Testing

The benefits of pharmacogenetic testing are clear, and yet, many patients and healthcare providers are not fully aware of its potential. Incorporating PGx testing into routine healthcare, especially before starting new medications, could help improve patient safety. A study published in The Pharmacogenomics Journal found that patients who underwent pharmacogenetic testing experienced fewer ADRs and higher satisfaction with their treatment plans.

Pharmacogenetics not only empowers healthcare providers to make informed decisions but also offers patients greater peace of mind. Knowing that their medications are tailored to their genetic profile can reduce anxiety and improve adherence to treatment, further supporting positive health outcomes.

A Call to Action: Improve Patient Safety

With hundreds of thousands of ADRs occurring each year, it is clear that more must be done to protect patients. Pharmacogenetic testing offers a powerful tool in the quest for personalized medicine, allowing healthcare providers to prescribe medications that are both safe and effective. Before starting any new medication, patients should consider undergoing a PGx test to ensure that their treatment is as safe as possible.

By embracing pharmacogenetics, we can move towards a future where drug treatments are tailored to the individual, reducing the risk of harm and improving the overall quality of healthcare.

References:

1. Canadian Pharmacogenomics Network for Drug Safety. (n.d.). About ADRs. Retrieved from https://cpnds.ubc.ca/about/#:~:text=Even%20if%20only%20the%20most,tens%20of%20thousands%20of%20deaths.
2. World Health Organization. (n.d.). Adverse Drug Reactions. Retrieved from https://www.who.int/news-room/fact-sheets/detail/patient-safety.
3. van Driest, Sara L., and Joshua C. Denny. "Pharmacogenetics for personalized medicine: translating science into practice." Human Genetics 139.6-7 (2020): 757-772.
4. Dunnenberger, Heather M., et al. "Implementation of a multidisciplinary pharmacogenomics clinic in a community health system." American Journal of Health-System Pharmacy 73.23 (2016): 1956-1966.
5. Adverse Drug Reaction (ADR) Canada. "Each Year, There Are an Estimated 200,000 Serious ADRs in Canada." ADR Canada. https://adrcanada.org/#:~:text=Each%20year%2C%20there%20are%20an,between%20%2413.7%20and%20%2417.7%20billion.
6. Dean, Laura. "Codeine Therapy and CYP2D6 Genotype." Medical Genetics Summaries, September 20, 2012. Updated March 8, 2016. National Center for Biotechnology Information (NCBI), U.S. National Library of Medicine. https://www.ncbi.nlm.nih.gov/books/NBK100662/.
7. Al-Harbi KS. Treatment-resistant depression: therapeutic trends, challenges, and future directions. Patient Prefer Adherence. 2012;6:369-88. doi: 10.2147/PPA.S29716. Epub 2012 May 1. PMID: 22654508; PMCID: PMC3363299.