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PRESCRIBING AND DISPENSING Prescriptions for compendial articles shall be written to state the quantity and/or strength desired in metric units unless otherwise indicated in the individual monograph (see also Units of Potency in these General Notices). If an amount is prescribed by any other system of measurement, only an amount that is the metric equivalent of the prescribed amount shall be dispensed. Units of Potency For substances that cannot be completely characterized by chemical and physical means, it may be necessary to express quantities of activity in biological units of potency, each defined by an authoritative, designated reference standard. Units of biological potency defined by the World Health Organization (WHO) for International Biological Standards and International Biological Reference Preparations are termed international Units (IU). Units defined by USP Reference Standards are USP Units, and the individual monographs refer to these. Unless otherwise indicated, USP Units are equivalent to the corresponding International Units, where such exist. Such equivalence is usually established on the basis solely of the compendial assay for the substances. For biological products, whether or not International Units or USP Units do exist (see Biological 1041), units of potency are defined by the corresponding U.S. Standard established by the FDA. USP Reference Standards USP Reference Standards are authentic specimens that have been approved by the USP Reference Standards Committee as suitable for use as comparison standards in USP or NF tests and assays. (See USP Reference Standards 11.) Currently official lots of USP Reference Standards are published in Pharmacopeial Forum. Where a USP Reference Standard is referred to in a monograph or chapter, the words “Reference Standard” are abbreviate to “RS”(see USP Reference Standards 11 ).Where a test or an assay calls for the use of a compendial article rather than for a USP Reference Standard as a material standard of reference, a substance meeting all of the compendial monograph requirements for that article is to be used. The requirements for any new USP or NF standards, tests, or assays for which a new USP Reference Standard is specified are not in effect until the specified USP Reference Standard is available. The availability of new USP Reference Standards and the official dates of the USP or NF standards, tests. Or assays requiring their use are announced via Supplements or Interim Revision Announcements. Reference Reagents Some compendial tests or assays require the use of specific reagents. These are supplied by USP when they might not be generally commercially available or because they are necessary for the testing and are available only to the originator of the tests or assay. Reagent Standards The proper conduct of the Pharmacopeial tests and assays and the reliability of the results depend, in part, upon the quality of the reagents used in the performance of the procedures. Unless otherwise specified, reagents are to be used that conform to the specifications set forth in the current edition of Reagent Chemicals published by the American Chemical Society. Where such ACS reagent specifications are not available or where for various reasons the required purity differs, compendial specifications for reagents of acceptable quality are provided (see Reagents, Indicators, and Solutions). Listing of these reagents, including the indicators and solutions employed as reagents, in no way implies that they have therapeutic utility; furthermore, any reference to USP or NF in their labeling shall include also the term “reagent” or “reagent grade.” Pharmacopeial Forum Pharmacopeial Forum (PF) is the USP journal of standards development and official compendia revision. Pharmacopeial Forum is the working document of the USP Council of Experts. It is intended to provide public portions of communications within the General Committee of Revision and public notice of proposed new and revised standards of the USP and NF and to afford opportunity for comment thereon. The organization of PF includes, but is Pharmaceutic Ingredients (Excipients) and for Dietary Supplements. Interim Revision Announcement (if present)—Official revisions and their effective dates, announcement of the availability of new USP Reference Standards, and announcement of assays or tests that are held in abeyance pending availability of required USP Reference Standards. In—Process Revision—New or revised monographs or chapters that are proposed for adoption as official USP or NF standards. Pharmacopeial Previews—Possible revisions or new monographs or chapters that are considered to be in a preliminary stage of development. Stimuli to the Revision Process—Reports, statements, articles, or commentaries relating to compendial issues. Nomenclature—Articles and announcements relevant to compendial nomenclature issues and listings of suggested and new United States Adopted Names (USAN) and International Nonproprietary Names (INN). Official Reference Standards—Catalog of current lots of USP Reference Standards with ordering information and names and addresses of worldwide suppliers. ATOMIC WEIGHTS AND CHEMICAL FORMULAS The atomic weights used in computing molecular weights and the factors in the assays and elsewhere are those recommended in 1997 by the IUPAC Commission on Atomic Weights and Isotopic Abundances. Chemical formulas, other than those in the Definitions, test, and assays, are given for purposes of information and calculation. The format within a given monograph is such that after the official title, the primarily informational portions of the monograph being introduced by a boldface double—arrow symbol. Graphic formulas and chemical nomenclature provided as information in the individual monographs are discussed in the Preface. Title The full title of this publication, including its supplements, is The Pharmacopeia of the United States of America, Thirtieth Revision, This title may be abbreviated to United States Pharmacopeia, Thirtieth Revision, or to USP 30. The United States Pharmacopeia, Thirtieth Revision, supersedes all earlier revisions. Where the term “USP” is used, without further qualification, during the period in which this Pharmacopeia is official, it refers only to USP 30 and any supplement(s) thereto. The same titles, with no further distinction, apply equally to print or electronic presentation of these contents. | 
