Here's how it works. Instead of a prescribed brand-name drug, your pharmacist frequently can select a less expensive generic equivalent. However, if your doctor writes on the prescription form that a specific brand-name drug is necessary, the prescription must be filled exactly as written. Many people can save money under their state's drug product selection law. A generic drug is called by its basic chemical name instead of a registered brand-name chosen by the manufacturer.
Generic drugs have the same active ingredients as brand-name drugs.
If your pharmacist gives you a generic drug in place of a brand-name product, good standard practice and most state laws require that it be generically and therapeutically equivalent. A generically equivalent drug product is one that has the same active ingredients, strength, and dosage form as its brand-name counterpart. For a drug to be therapeutically equivalent, it must be chemically the same and also must have the same medical effect. Some drugs are protected by patents and are supplied by only one pharmaceutical company. After the original patent expires, other manufacturers may be permitted to produce a generic equivalent, often sold at a lower cost.