I worked in medical drug research way back when Generics were just gaining popularity because they were a lot cheaper than Brand name pharmaceuticals. The government liked them too because they wanted them prescribed to Medicare and Medicaid patients to keep down their costs. So, the government passed the 80/20 Rule for generics.
First, I will quickly explain Bioequivalence versus Bioavailability concerning generic drugs. Bioavailability is the amount of unchanged active drug that reaches the blood stream so it can deliver the expected medicinal result. Pressed tablets and capsules contain a lot more ingredients than the active (magical) ingredient. There are binders, buffers, dehydrators, etc., and they all play a part in delivering the right amount of active drug to the blood stream to get the desired result.
Bioequivalence pertaining to generic drugs is the expectation that it will deliver the same amount of active ingredient to the blood stream to attain the same desired medicinal result as the Brand name drug.
However, the FDA cut the generic companies some slack by saying there can be a 20% variance in active ingredient reaching the blood stream – it could be 20% more or 20% less than the brand name drug. Okay, read that again (The 80/20 Rule).
What does that mean to your patients? In most cases it doesn’t seem to matter; however, there are some drugs that have a “Narrow Threshold” of tolerance (side-effects), and or 20% less active ingredient than the Brand Name drug may not be enough to achieve the desired medical result.
The manufacturing of generic drugs has improved over the past 20 years. But, if one of your patients is suddenly not getting the same results or is experiencing elevated side-effects, you may want to check their prescription to see if it looks the same as last month because the pharmacy may have changed manufacturers.