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Understanding generic drugs

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Your hospital formulary likely includes a large number of generic drugs. Generics provide good value for money and can free up budget for newer drugs that are not yet available in generic form. But multiple generics can be confusing for patients newly admitted to hospital – or indeed experiencing any transfer of care. With several different brands of the same medication available, it’s quite likely that patients were using a different brand at home or at another facility. They may need explanation and reassurance that they are in fact receiving the same drug.

There’s also a common misperception that generic drugs don’t work as well as brand name drugs because they are cheaper.

You can reassure patients that all generic drugs sold in Canada are designed to work the same way in the body as the original brand name drug. In Canada, generic and brand name drugs have identical active ingredients, and all generic drugs have been tested for bioequivalence.


What is bioequivalence? Bioequivalent drug formulations have the same bioavailability; that is, the same rate of absorption and the same extent of absorption. In other words, the active ingredient reaches the same concentration in the blood in the same amount of time.

Canada’s standards for bioequivalence are built upon internationally recognized criteria and are among the highest in the world. It’s a common misunderstanding that the concentration of the drug being tested can be 80 to 125 per cent of the drug it’s being tested against; in other words, that the variance can be up to 45 per cent and the drug will still meet the standard for bioequivalence. This is not true! The measurements – and their margins of error – must be within 80 to 125 per cent. This means the actual variance is generally less than five per cent.

Health Canada has set even stricter bioequivalence requirements for a few drugs that are highly toxic or have a narrow therapeutic range. These are known as critical dose drugs. For some critical dose drugs, such as those used to treat seizures or arrhythmias, there have been anecdotal reports of differences between brand name and generic drugs. However, you can reassure patients that controlled trials looking for increased toxicity or worsening of disease have consistently failed to show clinically important differences between brand name and generic drug use.

The bottom line is:

  • Generic and brand name drugs are bioequivalent.
  • Clinically important differences have not been reported in well-controlled trials.
  • Generic drugs create savings that can be redirected elsewhere.

For discharge planning, it’s interesting to note that research has shown patients are more likely to adhere to treatment when they are prescribed more affordable generic drugs.


So why do generic drugs cost less? Mostly because there is competition among generic drug companies. The company that first researched and developed the brand name drug initially holds a patent, so during this time no other company is allowed to sell it. When the patent expires, other companies are allowed to make copies of the drug. These generic drug companies don’t have to spend as much money marketing or studying the drug, which allows them to sell the drug at a lower price, and several companies may choose to manufacture and sell the same drug.

Different generic manufacturers may use different inactive ingredients such as “fillers,” flavours, or preservatives. This explains why different generic formulations may look slightly different, and this is only important for patients who are allergic to ingredients such as lactose, gluten, sulfites, or tartazine.

CADTH — an independent agency that assesses health technologies ― finds and summarizes the research on drugs, medical devices, and procedures. CADTH has created a series of tools to help you explain the facts about generic drugs. The tools are available free of charge at www.cadth.ca/generics.

If you need written information to share with patients, consider using CADTH’s Generic Drugs: Your Questions Answered. This easy-to-read handout, available in both English and French, covers similarities and differences between generic and brand name drugs, the reasons why generic drugs cost less, the Health Canada approval process, and more.


To learn more about CADTH, visit www.cadth.ca, follow us on Twitter: @CADTH_ACMTS, or talk to our Liaison Officer in your region: http://www.cadth.ca/en/services/liaison-officer.


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