Interestingly, the companies that develop the brand name products also manufacture the majority of all generic drugs. Some of these firms also distribute drugs made for them by generic companies. The FDA therefore requires that manufacturers submit proof of bioequivalency . Bioequivalence compares the rate, and the extent to which, the active ingredients of drugs are delivered to the bloodstream and to the site where the drugs work. Drugs that are bioequivalent produce the same therapeutic effects and are equally safe and effective.
Many states use the Orange Book to determine generic equivalency.
All 50 states have generic substitution laws that provide the basis for dispensing a generic product. If you are considering taking a generic medication, talk to your doctor or ask your pharmacist to check the FDA Orange Book to make sure that the drug is bioequivalent to the original product. A small number of drugs have known bioequivalence problems. Your pharmacist can advise which drug products are known to have generic equivalency problems. If you take a drug, such as prednisone or sulfasalazine, on a regular basis, try not to change from one generic or brand name product to another each time you renew your prescription.