The standards for bioequivalence in Canada are built upon internationally recognized standards and the criteria are amongst the highest in the world. Health Canada scientists ensure that the standards for bioequivalence are adhered to and kept up to date as they work closely with an expert panel of scientists, physicians, and pharmacists from across the country.
Bioavailability is a measure of the rate and extent to which the therapeutically active ingredient in a drug product is absorbed into the body. Bioavailability is assessed using two main variables: blood concentration over time; and, the maximum concentration of the active ingredient in the blood stream.
If two different drug products provide the same bioavailability, then they are bioequivalent. If a generic drug is bioequivalent to the brand-name version, there is no meaningful difference between them in terms of the drug’s safety and the way in which the drug works in the body. A bioequivalent generic drug is as safe and as effective as the brand-name version.
In a typical bioequivalence study, there are between 32 and 72 people tested. These individuals are separated into 2 groups and the study includes two periods.
In the first stage, Group 1 is given a generic drug and Group 2 is given the brand-name version of the drug. The extent of drug absorption based on the blood concentration of the drug over time, the maximum observed concentration of the drug and the time it takes to reach that maximum concentration are measured to assess the bioavailability of the drug in both groups of peoples.
At the second stage of the bioequivalence study, the group that received the generic drug in stage one is now given the brand-name drug, and the group that was given the brand-name drug is given the generic drug. The bioavailability of the drug in these two groups is assessed and measured in the same way as stage one. The bioavailability of the brand-name drug is then compared to that of the generic drug in each individual participating in the study. When these comparisons demonstrate a similar extent of absorption and a similar maximum drug concentration, bioequivalence is proven and the generic drug is confirmed to be as safe and effective as the brand-name version.
Scientifically Acceptable Variability – Every individual’s absorption and the maximum concentration achieved are unique; no one absorbs at the same rate as another person, and no single individual will absorb the exact same amount of the active ingredient at various times after drug administration, therefore health authorities have developed something called an “acceptable range of variability.” When testing a drug across a large number of people to determine a drug’s safety and effectiveness, variability must be part of the analysis because even though the drug is the same, everyone’s response will not be the same. This “acceptable range of variability” exists when testing a brand-name drug as well as when testing generic drugs.