Tuesday's report by the Canadian Institute of Health Information (CIHI) suggested more than 26,000 people aged 65 and older experienced an adverse effect of a drug that was given at the correct dose in 2010-2011.
Since 2006, the rate of hospital stays related to adverse events remained relatively stable as a proportion of all hospital stays for seniors, the report's authors said.
Blood thinners, often used to prevent heart attack and stroke, were the class of drugs most commonly associated with reactions like bleeding, at 12.6 per cent. Most of the bleeds were among people taking warfarin, a drug that needs to be closely monitored with blood tests to adjust the dose immediately if too high or too low.
Next were chemotherapy drugs, 12.1 per cent, and opioid painkillers at 7.4 per cent. Low white blood cell count from chemotherapy drugs and constipation from opioids were the most likely reasons for hospital stays based on drug classes.
"In some cases, other drugs can be given or diet changes can be recommended to avoid or reduce the risk of constipation, for example," said Jordan Hunt, CIHI's manager of pharmaceuticals in Ottawa. "But it's really starting at that low dose and working your way up to find the balance between pain relief and side-effects."
Michael Gaucher, the institute's director of pharmaceuticals and health workforce information services, said while it's often appropriate for people to be using these medications, seniors, their caregivers and health professionals should manage the risks.
To minimize the risk, seniors should regularly review medications, including those taken without a prescription, with their doctor and pharmacist and let them know about any changes, geriatricians recommend.
The report's authors suggest the electronic drug information systems rolling out in provinces could also help provide more complete information on patients' medications.
Costs $35.7M a year
In the study, it was common to change the dose of blood thinners and opioids after a hospital stay related to adverse drug reactions (ADRs).
Last year, researchers at the Institute of for Clinical Evaluative Sciences estimated that emergency department visits and hospital admissions due to adverse drug reactions among seniors in Canada cost an estimated $35.7 million. More than 80 per cent of those costs were related to hospital care.
A patient's age and sex, other illnesses, number of drugs, number of pharmacies visited, number of prescribers and hospitalizations are known to increase the risk of adverse drug reactions.
Over the same study period, one in 1,000 Canadian non-seniors had an ADR-related hospitalization.
The report's authors said the hospital data they looked back on likely underestimated the prevalence since data could be missing or inaccurately recorded. The drug-claims data used in the analysis came from a national database on prescription drug use based on linkable data from Alberta, Manitoba and P.E.I.
The study looked back at emergency visits and hospital admissions, and data could be missing or inaccurate, the authors said.Source: CIHI