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Rules for Coining Names

By definition, nonproprietary names are not subject to proprietary trademark rights but are entirely in the public domain. This distinguishes them from the trademarked names that have been registered for private use. A United States Adopted Name (USAN) is a nonproprietary name selected by the USAN Council according to principles developed to ensure safety, consistency and logic in the choice of names.

These principles take into account practical considerations, such as the existence of trademarks, international harmonization of drug nomenclature, the development of new classes of drugs and the fact that the intended uses of substances for which names are being selected may change.

Guiding principles

1.  A nonproprietary name should be useful primarily to health care practitioners, especially physicians, pharmacists, nurses, educators, dentists and veterinarians.

a.  The primary criterion for judging usefulness is suitability, including safety for use in the routine processes of prescribing, ordering, dispensing and administering drugs throughout the United States.
b.  The second criterion is suitability for use in educational programs for students in medically oriented professions and for use in scientific and lay publications.
c.  The third criterion is suitability for use internationally in drug identification, the exchange of information and translation into different languages.

2.  Attributes that contribute to usefulness are simplicity (brevity and ease of pronunciation), euphony and ready recognition and recall.

a.  The name for the active moiety of a drug should be a single word, preferably with no more than four syllables.
b.  The name for the active moiety may be modified by a single term, preferably with no more than four syllables, to show a chemical modification, such as salt or ester formation.  Examples can include cortisone acetate from cortisone, cefamandole sodium from cefamandole or erythromycin acistrate from erythromycin.
c.  Only under compelling circumstances is a name with more than one modifying term acceptable.  Compelling circumstances may pertain to such examples as pharmaceuticals containing radioactive isotopes or the different classes of interferons.
d.  Acronyms, initials and condensed words may be acceptable in otherwise appropriate terminology.

3.  A name should reflect characteristics and relationships that will be of practical value to the users.

a.  A common, simple word element (a "stem") should be incorporated in the names of all members of a group of related drugs when pertinent, common characteristics can be identified, such as similarity of pharmacological action.  When pharmacological similarity is found in drugs of distinctly different chemical nature, stems should differ.
b.  Distinctive terminology should be used for specific drugs or groups (e.g., insulin I 131, dextran 40, interferon alfa-2a and interferon alfa-n1; licryfilcon A and licryfilcon B; epoetin alfa and epoetin beta).

4.  A name should be free from conflict with other nonproprietary names and with established trademarks and should be neither confusing nor misleading.

5.  Preferences should be given to names of established usage provided they conform to these guiding principles and are determined to be free from conflict with existing nonproprietary names and trademarks.

6.  Whenever possible, the USAN Council will assign substances to existing stems or nomenclature schemes that describe the substance, its action, or its use.  A new stem will be created only in the unusual circumstance where existing stems and nomenclature schemes do not accurately represent a compound, its action, structure or use, and also when substantial clinical and preclinical data support the creation of a new stem.

7.  Identical negotiations submitted by two or more manufacturers will be conducted in accordance with the Council's practice of maintaining confidentiality.  The applicants involved will not be notified of the multiple sources of the submission.  However, the name selected by the USAN Council wil need to be accepted by each sponsor involved in the negotiation process.

8.  A request for a USAN should be made after the drug sponsor has submitted an Investigational New Drug (IND) application to the Food and Drug Administration (FDA) to obtain permission to initiate studies on humans.  An IND number is required before the USAN application review process can begin.

9.  Negotiations can be placed on hold

a.  The USAN Council Secretariat will put an ongoing negotiation on hold for six months, plus one additional three-month extension upon receipt of a written request from the manufacturer.  If the USAN Council has selected a name candidate and recommended this name to the manufacturer, the maximum hold is one six-month period.
b.  The negotiation will be canceled after the maximum nine-month hold has lapsed.
c.  If the negotiation is to be reopened at a later time, it will receive a new USAN file number and will be treated as a new application.  The manufacturer will be expected to submit a new USAN application form, update the background information and submit the appropriate fee.

Specific nomenclature rules

  Prefixes that imply "better," "newer" or "more effective;" prefixes that evoke the name of the spnsor, dosage form, duration of action or rate of drug release should not be used.  Examples include "dura," "forte," or "efex."

2.  Prefixes that refer to a Latin or Greek number, unless meaningful to the compound, are not acceptable.  Examples include the use of number references such as "deci," "centi," "bi" or "di").

3.  Prefixes that refer to an anatomical connotation or medical condition are not acceptable.

4.  Prefixes that indicate a chemical element or compound (Ca, Ni and Stannous) are not acceptable.

5.  Because of the international exchange of drug information, specific guidelines have been formulated to ensure appropriate translation of nonproprietary names into other languages.  The following rules of preferred spelling should be used when coining USAN designations:

a.  the letter "f" should be used instead of "ph"
b.  the letter "t" should be used instead of "th"
c.  the letter "e" should be used instead of "ae" or "oe"
d.  the letter "i" should be used instead of "y"
e.  the letter "h" should be avoided
f.  the letter "k" should be avoided
g.  the letter "j" should be avoided
h.  the letter "w" should be avoided
i.  "ar," "rac," "lev," "dex" or "es" are reserved for stereochemical configurations

6.  Additionally, these letter combinations are restricted until further notice.  Please avoid the following prefixes:

a.  the beginning letter combination of "me"
b.  the beginning letter combination of "str"
c.  chemical connotations such as "ben," "bu," "cat," "cel," "fen," "flu," "fo(s)" and "piro," unless chemically appropriate
d.  chemical symbols unless present in the compound "al," "ba," "ca," "li" and "ni"
e.  "z" or "x" as a beginning letter

7.  Isolated letters, numbers or hyphenations are restricted to those groups of substances for which usage fulfills a clearly demonstrable purpose.  Examples of this include interferon alfa-2b, paflufocon A or technetium Tc 99m siboroxime.

8.  Group relationships in a name preferably should be indicated by use of syllables or stems.  Conversely, use of the stem for other than the appropriate group should be avoided.  When multiple stems are available, the stem conveying the most information should be used.

9.  Esters, salts, chelates, prodrugs and complexes ordinarily require a two-word name to indicate the inactive as well as the active portion.

a.  The preferred order for the name of an inorganic salt is cation-anion (e.g., sodium chloride), irrespective of the clinically significant portion.  The same order is preferred for well-known salts of simple organic acids such as sodium lactate, magnesium citrate and potassium acetate.

b.  For more complex organic compounds, the pharmacologically active portion should be identified first.  Examples of this include oxacillin sodium and dexibuprofen lysine.

c.  A name for a salt or ester is generally derived from the name of the pharmacologically active moiety or corresponding acid.  An example is chloroprednisone acetate.

d.  Ester prodrugs, which are cleaved in vivo to release the pharmacologically active species, ordinarily receive two-word names (e.g., haloperidol decanoate, clindamycin palmitate).  Other types of prodrugs may receive a one or two-word name, as the USAN Council deems most appropriate.

e.  Exceptions to two-word names may be appropriate when differences in pharmacologic activity for the ester form are clinically important; for example, if only the ester but not the parent is pharmacologically active.  To receive a one-word designation for an ester, sponsors must submit data to document the activity of the ester.  The USAN Council may request such information if it is not provided with the application.    

10.  As of January 2013, the name for the salt form of a pharmacologically active moiety will no longer specify the number of molecules used to react with the active moiety. Between January 1993 and December 2012 a different rule was in effect, and numerical prefixes were often used to specify the number of molecules used to react with the active moiety (e.g., basalazide disodium).

11.  A name for a quaternary ammonium substance should designate the cation and anion separately.  Octonium bromide not octonine methylbromide, for example.  The name assigned to the cation must contain the -ium suffix stem.  This rule is modified when a second, more pertinent, stem is used to coin a new name.  In such cases, the addition of the -ium suffix stem to solely designate a quaternary ammonium is not required.

12.  A name for a complex of two or more components should list the name of the principal active ingredient followed by a coined designation for the second component ending with an "-ex" suffix to indicate "complex" such as in bisacodyl tannex or doxycycline fosfatex.  Complexes formed from sulfonated diethenylbenzene-ethenylbenzene copolymers and an active ingredient should list the name of the principal active ingredient followed by "polistirex," such as in chlorpheniramine polistirex or codeine polistirex. 

13.  A name for a drug containing a radioactive atom should list, in the order given:  1)  the name of the drug containing the radioactive atom; 2) the element symbol; 3) the iostope number, and 4) the name of the carrier agent, if any (examples of this include rose bengal sodium I 131, cyanocobalamin Co 60, potassium bromide Br 82, technetium Tc 99m butilfenin, technetium Tc 99m medronate, indium In 111 oxyquinoline, indium In 111 satumomab pendetide).

14.  A name for a substance generally should not indicate the state of hydration, the morphology, or the mode of preparation.  Reference to the water of hydration is retained in the chemical information (chemical names, formulas, weight) but is excluded from the nonproprietary name.  The degree of hydration becomes a part of the chemical entity identified by the USAN.

15.  Under the terms of the Orphan Drug Act of 1983, the development and marketing of drug products that are of limited commercial application but that are potentially useful in relatively rare disease conditions are encouraged.  The selection of a name for an orphan drug may be based on special considerations.  Therefore, when the name for an orphan drug appears to follow a more chemically oriented terminology style than is customary for drug nomenclature generally, this is not to be regarded as a basis or a precedent for a future selection of a USAN.

16.  A name coined for a new chemical entity routinely does not specify the steroisomeric form of the molecule in the nonproprietary name.  If the stereochemical configuration has been determined, this information is presented in the chemical name(s) and is reflected in the structural formula.  A USAN can, therefore, identify the racemic mixture (e.g., carnitrine, ibuprofen, tetramisole) the levo isomer (e.g., remoxipride, quadazocine), or the dextro form (e.g., butopamine).  Subsequently, if a name is needed for a different enantiomer or for the racemic form, the following prefixes should be added to the existing name:

a.  For the racemate, the rac-/race- prefix is used (e.g., racemethionine, racepinephrine, ractopamine).
b.  For the levorotatory form, the "(S)" isomer, the lev-/levo- prefix is used (e.g., levocarnitine, levamisole, levcromakalim, levdobutamine).
c.  For the levorotatory form, the "(R)" isomer, ["R(-)"-isomer], the "ar-" prefix is added to the base name.
d.  For the dextrorotatory form, the "(R)" isomer, the dex-/dextro- prefix is used (e.g., dexamisole, dexibuprofen, dextroamphetamine, dexverapamil, dexrazoxane, dexfosfoserine, dexniguldipine)
e.  For the dextrorotatory form, the "(S)" isomer ["S(+)"-isomer], the "es-" prefix is added to the base name.

17.  Official names have been selected for a number of radicals and adducts used to form salts or esters of the pharmacologically active moiety.  In a majority of cases, these names represent contractions of the chemical name assigned to the radical or adduct.  In some cases, the official name identifies a multicomponent adduct.