Adverse Drug Reactions

Adverse drug reactions (ADRs) are the unintended responses or harmful side effects (expected or unexpected) caused by the normal dose of a drug. ADRs are among the top ten causes of all deaths in North America. Many of these ADRs are caused by inherited genetic differences.


A severe ADR known as Stevens Johnson syndrome

Implications for Health Care

The paradox of modern drug development is that initial trials provide evidence about efficacy and preliminary safety for a medication at a standardized dose in a large population, while physicians treat individual patients who often differ in their response to drug therapy, sometimes with devastating results.

The annual cost of ADRs has been estimated to be over $13 billion in Canada. This is likely an underestimation, since 95% of ADRs are not reported to regulators. Even if only the most severe ADRs are considered, there are an estimated 200,000 ADRs each year in Canada resulting in hospital admission and causing tens of thousands of deaths.

The cost of a genetic test to prevent ADRs will be offset by savings in medical care that would have been used to care for the patient after the resulting reaction.

CPNDS Target ADRs CPNDS chooses ADRs for targeted surveillance because of the seriousness and long-term consequences of the ADR and the likelihood that the cause was genetic.

  • Cisplatin-induced hearing loss
  • Anthracycline-induced heart damage/failure
  • Opiate intoxication of breastfed infants
  • Vincristine-induced neurotoxicity
  • Hypersensitivity syndrome (HSS) caused by carbamazepine
  • Warfarin pharmacogenetics in children