Background: The core motive of pharmacovigilance is the detection and prevention of adverse drug reactions (ADRs), to improve the risk-benefit balance of the drug. However, the causality assessment of ADRs remains a major challenge among clinicians, and none of the available tools of causality assessment used for assessing ADRs have been universally accepted. Objective: To provide an up-to-date overview of the different causality assessment tools. Methods: We conducted electronic searches in MEDLINE, EMBASE, and the Cochrane database. The eligibility of each tool was screened by three reviewers. Each eligible tool was then scrutinized for its domains (the reported specific set of questions/areas used for calculating the likelihood of cause-and-effect relation of an ADR) to discover the most comprehensive tool. Finally, we subjectively assessed the tool's ease-of-use in a Canadian, Indian, Hungarian, and Brazilian clinical context. Results: Twenty-one eligible causality assessment tools were retrieved. Naranjo's tool and De Boer's tool appeared the most comprehensive among all the tools, covering 10 domains each. Regarding "ease-of-use" in a clinical setting, we judged that many tools were hard to implement in a clinical context because of their complexity and/or lengthiness. Naranjo's tool, Jones's tool, Danan and Benichou's tool, and Hsu and Stoll's tool appeared to be the easiest to implement into various clinical contexts. Conclusion: Among the many tools identified, 1981 Naranjo's scale remains the most comprehensive and easy to use for performing causality assessment of ADRs. Upcoming analysis should compare the performance of each ADR tool in clinical settings.

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Background Patients with chronic or acute/postoperative pain frequently use opioids. However, opioids may cause considerable adverse reactions (ARs), such as respiratory depression, which could be lethal. Unfortunately, only 5% of drug-related ARs (including those to opioids) are reported to health authorities. Therefore, little is known regarding the occurrence of opioid-related ARs at the population level. Objective The aim of this study was to investigate how the rates of reported opioid-related ARs have changed in Canada since 1965. Methods Our retrospective study examined trends of reported opioid-related ARs occurring in hospitalized and outpatients. Data on opioid-related ARs and mortality between 1965 and 2019 were obtained from the Canada Vigilance and Statistics Canada databases. Descriptive and Joinpoint regression analyses were performed. Results Oxycodone and normethadone were the most and least involved opioid agents, respectively, among the 18,407 reported ARs. The highest rate of reported opioid ARs (3.8 per 100,000 person-years) was recorded in 2012, whereas the lowest was recorded in 1965 (0.1 per 100,000 person-years).

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