The USP and NF allow the simultaneous use of both the metric and apothecary systems to declare the quantity of active ingredients present in drug product labeling. Prior to USP XX and NF XV, the official compendia allowed the approximate equivalent of the exact quantity to be enclosed in parenthesis; such as Quinidine Sulfate 200 mg. (3 grains).
On July 1, 1980 the USP XX and NF XV became official and requires that "Where expressed in both the metric and apothecary systems, statements of quantity or strength in the labeling of drug products shall utilize the exact equivalent." (See inside back cover USP XX and NF XV). Therefore the above example would now have to be modified to read Quinidine Sulfate 200 mg (3.086 grains).
USP and NF products shipped after 7/1/80 bearing a dual declaration will be considered misbranded if the exact equivalents are not used. However, as a general rule we are not prepared to initiate regulatory action of this violation alone. It may be included as a 502(g) charge only when other violations exist or it may serve as the basis for a Notice of Adverse Findings letter.