Adverse drug reactions (ADRs) are a public health problem that is partly preventable with sufficient information and appropriate action. ADRs lead to visits to physicians’ offices and emergency departments, admissions to hospital, problems while in hospital and, in some cases, death. It is estimated that approximately 50% of serious ADRs, those resulting in hospital admission, are preventable.[1,2] Prevention can be achieved by careful drug administration, that is, dosing appropriately, monitoring adequately, attending to allergies, and avoiding drug interactions and contraindications. In rare cases, prevention is attained by removing drugs with an unacceptable balance of benefit versus risk from the market.

Preventing ADRs thus requires adequate information on drug toxicity, which comes from both premarketing and postmarketing data. Premarketing clinical trials, restricted to a relatively small number of “ideal” patients for a limited time, were unable to predict the need for safety warnings in 10% of drugs recently marketed in the US, with 3% of drugs ultimately withdrawn from the market after approval.[3] Postmarking surveillance, or pharmacovigilance, is therefore necessary. Formal postmarketing studies including cohort studies should be performed, but enormous resources would be required to study every medication on the market. Case reports are the most practical and cost-efficient method of postmarketing surveillance, covering all marketed drugs in real-life situations in millions of people over long periods of time. Case reports are effective, providing the basis for many drug safety advisories from Health Canada or industry, such as those describing pure red cell aplasia in patients taking epoetin alfa (Eprex) (www.hc-sc.gc.ca/hpb-dgps/therapeut/zfiles/english/advisory/industry/eprex2_e.html [9]), with recommendations to reduce its likelihood, or withdrawal of kava due to hepatotoxicity (www.hc-sc.gc.ca/english/protection/warnings/2002/2002_56e.htm [10]).

In British Columbia, over 600 reports are sent annually to the BC Regional ADR Centre, the local centre for pharmacovigilance set up by Health Canada. These reports, of which nearly two-thirds describe serious reactions and one-sixth involve reactions that are both serious and unexpected, have added to Canadian drug safety information, safety advisories, and drug withdrawals. Since Canada participates in the international monitoring program of the World Health Organization, reports from British Columbia have contributed to the WHO database of almost 3 million reports used to detect early safety signals.[4]

New initiatives to enhance our drug safety system include the creation of the Marketed Health Products Directorate of Health Canada, with $7 million in new funding for postmarketing surveillance in the 2002–03 fiscal year.5 Health Canada is negotiating with the FDA to create a combined US - Canada database, to aid in the fast detection of drug safety problems.[5] And a free listserv provided by Health Canada enables you to receive new drug safety advisories by e-mail as soon as they are available. Subscribe at: www.hc-sc.gc.ca/hpb-dgps/therapeut/htmleng/adr.html [11].

The Health Canada reporting program is completely confidential. It takes only 2 minutes to fill out a report form—there is a copy in every CPS and on the Health Canada website (www.hc-sc.gc.ca/hpb-dgps/therapeut/zfiles/english/forms/adverse_e.pdf [12])—and fax it to your local ADR centre at 1 866 678-6789 (toll free). Alternatively, use e-mail (adr@dpic.bc.ca [13]) or the toll free telephone number (1 866 234-2345). It is not necessary to report all reactions. Think of the acronym SUN, and report reactions if they are Serious, or Unexpected, or involve a New drug (on the market for 5 years or less). An estimated 90% of ADRs are never reported;[5] we can do better.

For vaccines, there is a separate form, which can be obtained from your local medical health officer. Alternately, the report of a vaccine associated adverse event can be made to your local public health department by telephone.

—Barbara Cadario, BSc, BScPhm, MSc
Program Coordinator, BC Regional ADR Centre
BC Drug and Poison Information Centre

References

1. Winterstein AG, Sauer BC, Hepler CD, et al. Preventable drug-related hospital admissions. Ann Pharmacother 2002;36:1238-1248.PubMed Abstract [14]
2. McDonnell PJ, Jacobs MR. Hospital admissions resulting from preventable adverse drug reactions. Ann Pharmacother 2002;36:1331-1336.PubMed Abstract [15]
3. Lasser KE, Allen PD, Woolhandler SJ, et al. Timing of new black box warnings and withdrawals for prescription medications. JAMA 2002;287:2215-2220.PubMed Abstract [16]
4. The Uppsala Monitoring Centre. The importance of pharmacovigilance. United Kingdom: World Health Organization, 2002:9.Full Text [17]
5. Response to the recommendations to Health Canada of the Coroner’s Jury Investigation into the death of Vanessa Young. http://www.hc-sc.gc.ca/english/protection/vanessa_young/index.html  [18](27 August 2002; retrieved 6 January 2003).