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Recent reports of considerable variation in the serum levels, and therefore in the probable biological activities, of equal doses of certain drugs marketed by different manufacturers, focus attention upon an important determinant of drug efficacy. These variations indicate that therapeutic equivalence, or equal biological activity, cannot necessarily be inferred from equivalence in the chemical constitution of different formulations of the same drug. In the Drug Efficacy Study, it has been found that, in many cases, no data bearing on biological activity of chemically equivalent drugs are available other than those submitted by the manufacturer who originally filed a New Drug Application for his product. For this reason, the following qualifying addendum was approved by the Policy Advisory Committee of the Drug Efficacy Study and was forwarded to the Food and Drug Administration with each of the 26 groups:
Drugs of identical chemical composition (so-called generic drugs) formulated and marketed by
Castle WB, Astwood EB, Finland M, Keefer CS. White Paper on the Therapeutic Equivalence of Chemically Equivalent DrugsPrepared by a Subcommittee of the Policy Advisory Committee, Drug Efficacy Study. JAMA. 1969;208(7):1171-1172. doi:10.1001/jama.1969.03160070049012