What are Adverse Drug Reactions and how can they be prevented?

An adverse drug reaction (ADR) is a noxious unintended consequence of taking a normal dosage of a drug,[1] usually prescribed to an individual by a medical professional, that was properly administered and which was supposed to be beneficial for the patient towards curing a disease or sickness. A sick patient, anyone ranging from a child with the common cold visiting their pediatrician to an adult patient with a severe form of cancer in the intensive care unit, may be given a medication to take which they nor the administrator of the medication is aware that they are allergic to and their body will respond negatively to that drug. A 2013 Canadian Institute of Health Information report stated that between 2010 and 2011 more than 27,000 Canadians aged 65 and older suffered from an ADR.[2] The consequences of an ADR may include damage to the proper functioning of a patient’s body internally and/or externally, prolonged hospitalization, significant disability/incapacity, life-threatening injuries, congenital anomaly and even death.[3]

Costs associated with ADRs significantly add to health care expenditures in an era where health care spending already eats up roughly 50% of the annual budget in some provinces. In a 2011 study which examined 1,000 patients admitted to the emergency department at Vancouver General Hospital, 122 or 12.2% were in the department due to an adverse drug event. Of these patients, 48 were present because of an ADR (one type of adverse drug event defined as an unintended response that occurred despite use of an appropriate drug dosage). After adjustment, patients with adverse drug events had a higher risk of spending additional days in the hospital per month (6.3% versus 3.4%) and higher rate of outpatient health care encounters (1.73 versus 1.22), and the adjusted median monthly cost of care was 1.90 times higher (Can $325 versus $96).[4] It was estimated that the added cost could be as much as $49 million annually.[5] These financial costs are in addition to the physical and psychological costs endured by ADR patients. Furthermore, the number of deaths resulting from ADRs is staggering. In Canada, they cause 10,000 to 22,000 deaths and cost the Canadian healthcare system over $13 billion per year.[6] In the United States, another developed country, 26,500 children die from ADRs each year.[7]

Advances in Genomics

Until just recently, there was little, if not anything, that could be set in place to prevent ADRs and thus Canadian governments have not taken direct action on preventing ADRs. However, recent scientific advancements in the past decade have produced concrete evidence to demonstrate that ADRs can be prevented by making use of genomics.

Every individual is made up of various genes, which are inherited from their parents and determine the traits they will develop, from whether they will have curly or straight hair, to how they will respond to certain medications. When some genetic variants in a cluster of immunity genes combine with certain medications, they can produce a negative reaction, an ADR.[8] Scientists in several jurisdictions, including Asia, Europe and the USA have identified destructive drug-gene combinations.[9]

Today, technology has developed to the point that a simple test can be conducted which extracts DNA and sequences it to determine which genes and which gene variants an individual possesses. This information can help us in preventing ADRs and this evidence is the basis of our policy for supporting publicly funded genetic screening.


[1] World Health Organization, International Drug Monitoring: The Role of National Centres, Report of WHO Meeting  (World Health Organization Technical Report Series) (Geneva, Switzerland: WHO, 1971), 9.

[2] Canadian Institute for Health Information, “Adverse Drug Reaction–Related Hospitalizations Among Seniors, 2006 to 2011,” March 2013, accessed August 18, 2016 from https://secure.cihi.ca/free_products/Hospitalizations%20for%20ADRENweb.pdf

[3] World Health Organization, The Conceptual Framework for the International Classification for Patient Safety Version 1.1 (Final Technical Report) (Geneva, Switzerland: WHO, 2009), 104.

[4] Corinne M. Hohl et al., “Outcomes of emergency department patients presenting with adverse drug events,” Annals of Emergency Medicine 58, 3 (2011): 270.

[5] “Adverse drug events costly to health care system: Vancouver Coastal Health-UBC research,” University of British Columbia press release, February 25, 2011, accessed August 9, 2016 from http://news. ubc.ca/2011/02/25/adversedrug-events-costly-to-health-care-system-vancouver-coastal-health-ubc-research/

[6] “Genotype-Specific Approaches to Therapy in Childhood: The Canadian Pharmacogenomics Network for Drug Safety,” Genome British Columbia, accessed August 9, 2016 from http://www.genomebc.ca/researchprograms/projects/health/completed/genotype-specific-approaches-to-therapy-in-childhood-the-canadia/

[7] “Genotype-Specific Approaches to Therapy in Childhood (GATC),” Genome Canada, accessed August 9, 2016, http://www.genomecanada.ca/en/genotypespecificapproachestherapychildhoodgatc

[8] Ed Yong, “When a Genetic ID Card Is the Difference Between Life and Death,” The Atlantic, October 5, 2015, accessed August 9, 2016, http://www.theatlantic.com/science/archive/2015/10/southeastasiageneticdisorderstevensjohnsonsyndrome/408736/

[9] Ibid.

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