Myth: If a drug makes it to market, it's safe for everyone

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Myth busted October 2010

Pharmaceuticals save many human lives and improve the quality of numerous others. For example, thanks to new antiretroviral therapies, AIDS—once a rapidly progressive and deadly disease—is now a manageable chronic condition. And chronic conditions such as diabetes can be managed with a range of medications tailored to patients’ needs. With these advancements in pharmacology, it’s no wonder that Canadians generally trust that the drugs they use are safe and effective. Furthermore, according to a recent poll, Canadians have confidence in public authorities and drug companies to keep them healthy and safe.[i]

Despite the various measures in place to enhance drug safety, adverse drug reactions remain one of the top 10 leading causes of death in Canada.[ii] Research shows that hospital admissions from adverse reactions are high and that many are preventable.[iii, iv] Experts estimate that over 95% of adverse reactions go unreported.[v

Out with the mould, in with the new?

Drugs have been used for millennia, ever since certain plants were observed to have healing properties. For example, extracts of willow bark have been used for centuries to reduce fever. These extracts contain a chemical similar to aspirin. However, pharmacology as a science has existed for just around two centuries.[vi] Some important discoveries were serendipitous like the finding that penicillin —a by-product of a type of mould—can cure infection. However, in recent decades drug R&D has become increasingly sophisticated. Drugs can now be developed to isolate specific protein molecules in target tissues (e.g. Tamoxifen interferes with a specific hormone receptor in breast cancer cells).

Progress in drug science makes it tempting to assume that “newer” means “better and safer”. However, researchers caution against this thinking, advising physicians not to prescribe new (and usually more expensive) treatments when existing ones will do.[vii] In fact, new drugs have a one in five chance of being stamped with a “black box warning” (required by the U.S. Food and Drug Administration if a drug may have serious or even fatal side effects), or being withdrawn from the market within 25 years of approval (half of all withdrawals occur within two years of approval).[vii] Seen through this statistical lens, the newness of a drug does not guarantee its safety.

Drugs on trial


Before receiving regulatory approval, new drugs undergo clinical trial research to determine if the drug produces the intended effect. Trials also identify possible side effects and their associated harms. This information helps regulators weigh the benefits and harms of drugs.

However, clinical trials have limitations. Certain people (such as those that are old, young, pregnant or suffering from other medical conditions) may be excluded from clinical trials meaning that their susceptibilities to adverse reactions are not uncovered.[viii] This is especially concerning since the greatest users of pharmaceuticals are the elderly.[ix] As well, participation is often restricted to patients who would use the drug only for its intended application, which isn’t always the case. These trials cannot anticipate a clinician’s decision to prescribe “off-label” (prescribing an approved drug for an unapproved application) or in opposition to clinical guidelines. Furthermore, the international standard suggested for the number of participants in trials[x, xi] is not large enough to detect very rare but nevertheless serious adverse reactions.[viii]

Because clinical trials do not mimic real life, the occurrence of unexpected adverse reactions is almost inevitable in the post-market setting. In fact, research shows that pre-market clinical trials only detect about half of all serious adverse reactions that surface once the drug is in widespread use.[xii]          

The ultimate trial


Once a new drug is approved (and only a handful are approved annually), it is put to the ultimate test of safety: application in the market. However, it may require years of drug exposure before any safety concerns about adverse reactions become apparent. In Canada and the U.S., drug companies are required to report adverse reactions to the federal government, whereas healthcare professionals and the public are encouraged to report on a voluntary basis. The voluntary element leads to underreporting, making it impossible to know the true frequency and severity of adverse reactions. In addition, the typical prescriber often cannot identify or is unaware of the full spectrum of a drug’s harms due to unreported adverse reactions. This lack of information can undermine efforts to prescribe only the safest drugs.



It cannot be assumed that progress in drug science means that all drugs on the market are safe for everyone. There is no “magic bullet” drug that offers all benefit and no harm (for example, some people have allergic reactions to penicillin that can be fatal). Ultimately, it is up to patients and families, in consultation with a health professional, to decide whether to take a drug. What’s most important is having a thorough understanding of the potential benefits and harms of any drug so that informed decisions may be made. In this respect, the recent establishment of the federally-funded Drug Safety and Effectiveness Network,[xiii] which will fund research on the safety and effectiveness of drugs in the “real world”, is a step in the right direction. The bottom line is that the more information we have available, the more we are able to understand the impact of adverse reactions on individuals, the healthcare system and the economy.[v]

This issue of Mythbusters is based on an article by the 2010 Mythbusters Award recipient, Ms. Tenneille Loo. Tenneille is a master’s candidate at the University of British Columbia, Vancouver, B.C.

Mythbusters articles are published by the Canadian Health Services Research Foundation (CHSRF) only after review by experts on the topic. CHSRF is an independent, not-for-profit corporation funded through an agreement with the Government of Canada. Interests and views expressed by those who distribute this document may not reflect those of CHSRF. © 2010.