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Definition of Therapeutic Equivalence
Therapeutic Equivalence – in pharmacology, drugs that have the same active ingredients in the same forms and have the same actions within the body.
Therapeutically equivalent drugs may have superficial differences such as in appearance (shape or color) and the inactive ingredients that serve as the vehicle to contain the active ingredient. However, they must have the same BIOAVAILABILITY and efficacy.
The FDA has adopted a BIOEQUIVALENCE standard based on a statistical methodology in which the time it takes for each drug to reach its maximum concentration in the BLOOD circulation and the amount of time the drug remains at a THERAPEUTIC LEVEL in the blood circulation differ by no more than 20 percent. In its official listing of approved drugs, The Orange Book, the FDA identifies all drugs with alternate products as “A” drugs (therapeutically equivalent) or “B” drugs (not therapeutically equivalent).
Health-care providers other than pharmacists sometimes use the term therapeutic equivalence in the context of different drugs within the same classification that have similar effects—for example the drugs fluoxetine and sertraline, both of which are selective serotonin reuptake inhibitors (SSRIs) to treat depression. Though these drugs act in similar ways to achieve a similar therapeutic effect, they do not have the same active ingredients.