Final answer:
The difference in the rate and extent to which a brand name drug vs a generic drug becomes available to the site of action can be measured as the therapeutic equivalence of the drugs. Generic drugs are produced after the patent for a brand name drug expires and must demonstrate that they have the same active ingredient, strength, dosage form, and route of administration. However, there may be slight differences in absorption between the two due to variations in inactive ingredients and manufacturing processes.
Step-by-step explanation:
The difference in the rate and extent to which a brand name drug vs a generic drug becomes available to the site of action, given the same dose and condition, can be measured as the therapeutic equivalence of the drugs.
When a brand name drug is first developed, the pharmaceutical company holds a patent on it, which grants them exclusive rights to sell the drug. Once the patent expires, other companies can produce generic versions of the drug. To be considered therapeutically equivalent to the brand name drug, the generic drug must demonstrate that it has the same active ingredient, strength, dosage form, and route of administration as the brand name drug.
However, despite meeting these criteria, there may be slight differences in the rate and extent of absorption of the drug into the bloodstream between the brand name and generic versions. These differences can be attributed to variations in inactive ingredients and the manufacturing process of the drugs. Although these variations are generally considered to be within an acceptable range, some patients may experience differences in the effectiveness or side effects of the brand name and generic drugs.