In responding to Walter Maksymowych's letter about a recent CMAJ editorial1 and an article about leflunomide2 in the Canadian Adverse Reaction Newsletter (CARN), we would like to emphasize that every drug has benefits and risks. As its name implies, the CARN discusses mainly the risks associated with drugs rather than their benefits. Its purpose is to raise awareness of potential safety issues detected through the review of case reports submitted to Health Canada and to remind health care professionals of ways to minimize the risks. Publication of articles in the CARN is preceded by a comprehensive consultative process with scientific staff within Health Canada, the Regional Adverse Reaction Centres, members of the department's Expert Advisory Committee on Pharmacovigilance and the editor of CMAJ.
The leflunomide article2 summarized safety information from various sources (e.g., the Arava product monograph, the Australian Adverse Drug Reaction Bulletin and documents on leflunomide from the European Medicines Evaluation Agency), rather than drawing conclusions based solely on the adverse reaction data presented in the article. The data in the CARN represent observational results from the Canadian Adverse Drug Reaction Monitoring Program database. Prominent caveats in the newsletter advise readers that adverse reactions to health products are considered suspicions, because a definite causal association is often impossible to determine. Spontaneous reports of adverse reactions cannot be used to estimate the frequency of such events, because adverse reactions remain underreported, and patient exposure is unknown.
Health Canada continues to enhance its postmarketing surveillance and assessment program for health products; the spontaneous adverse reaction reporting system represents only one aspect of many activities in this area. Comprehensive risk-benefit evaluations include information from postmarketing surveillance on a global scale, which takes into account exposure to the drug in question and the results of epidemiologic research and clinical trials to determine whether a drug's benefits continue to outweigh its risks. Despite the limitations of spontaneous reporting systems and in the absence of complete evidence, it is well recognized that adverse reaction reports are but one of the factors that may contribute to a signal of potential problems. Drug safety is a shared responsibility, and health care professionals need to be made aware of all drug safety issues to enable informed therapeutic decision-making with their patients.
Ann Sztuke-Fournier Marielle McMorran Editors Canadian Adverse Reaction Newsletter Marketed Health Products Directorate Health Canada Ottawa, Ont.