Prescription drugs can be a costly medical expense, especially for older people and those who are chronically ill. However, each state has a law that lets pharmacists substitute less expensive generic drugs for many brand-name products. Depending on your prescription needs, your savings could be significant. Before you talk with your doctor or pharmacist about switching, there are things you need to know about generic drugs and the law.

What’s the difference between a generic and brand-name drug?

Not much, except for name and price. A generic drug is called by its chemcical name; a manufacturer assigns a brand name. The products have the same ingredients.
Standard practice and most state laws require that a generic drug be generically equivalent to its brand-name counterpart. That is, it must have the same active ingredients, strength, and dosage form—pill, liquid, or injection. The generic drug also must be therapeutically equivalent—it must be the same chemically and have the same medical effect.

Do all drugs have generic equivalents?

No. Some drugs are protected by patents and are supplied by only one company. However, when the patent expires, other manufacturers can produce its generic version. Currently, about half the drugs on the market are available in generic form.

How can I get generic drugs?

Talk with your doctor or pharmacist. Explain that you want the most effective drug at the best price. Ask your doctor to write prescriptions for generic drugs when possible.

Are there exceptions to the law?

Yes. If your doctor writes on the prescription form that a specific brand-name drug is required, your pharmacist must fill the prescription as written. That is, a generic drug cannot be substituted.
However, your pharmacist can talk with your doctor about the prescription. Perhaps there’s an acceptable generic drug that your doctor is not aware of. Your pharmacist can compare and evaluate generic and brand-name drugs and may be able to consult with your doctor to provide the right medication at the best possible price.

Will my doctor automatically prescribe generic drugs?

It depends on the physician. You can ask your doctor to write a prescription permitting substitution of a generic drug product when appropriate. You also can ask whether a generic product will be as effective and less costly. Or, you can request that only brand-name products be used to fill your prescriptions.

Where can I get more information?

The Food and Drug Admininstration has a toll-free hotline to answer questions about drug safety and efficacy. Call 1-800-532-4440. You also can visit the FDA at www.fda.gov—click on Human Drugs.

source: http://www.ftc.gov/bcp/conline/pubs/health/generic.htm