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Drugs With Inactive Components

Chapter:
Nomenclature
Author(s):

Margaret A. Winker

Drugs With Inactive Components

Drugs often contain a pharmacologically inactive component, eg, a base, salt, or ester, that is not responsible for the drug’s mechanism of action but lends stability or other properties to the drug. Drugs with both an active and inactive component generally require a 2-part name that provides the active and inactive portion of the drug. Inorganic salts and simple organic acids are named in the order cation-anion (eg, sodium chloride, magnesium citrate). For more complex organic compounds, the active component is named first (eg, oxacillin sodium).1(p1224)

Pharmacologically inactive components are generally salts, esters, and complexes. Sodium, potassium, chloride, hydrochloride, sulfate, mesylate, and fumarate are common components of salts.

acyclovir sodium

midazolam hydrochloride

benztropine mesylate

morphine sulfate

Quaternary ammonium salts usually are designated by a 2-part name and have the suffix -ium on the first word of the name.

atracurium besylate

alcuronium chloride

octonium bromide

Salts and esters are frequently designated by the ending -ate. Three-word names are used for compounds that are both salts and esters.

clomegestone acetate [ester]

hydrocortisone valerate [ester]

testosterone cypionate [ester]

methylprednisolone sodium phosphate [salt and ester]

roxatidine acetate hydrochloride [ester and salt]

If more than one pharmacologically inactive molecule interacts with the pharmacologically active component, the number of molecules is reflected in the name. If the number is not designated, the number of molecules is assumed to be 1.1(p1224)

balsalazide disodium [2 sodium molecules]

gusperimus trihydrochloride [3 hydrochloride molecules]

besipirdine hydrochloride [1 hydrochloride molecule]

Complexes of 2 or more components may include a term ending in -ex to indicate a complex.

bisacodyl tannex

nicotine polacrilex

codeine polystirex

Chemical names are often too complex for general use. In such cases, shorter nonproprietary names may be created. For example, for the drug erythromycin acistrate, acistrate refers to the 2′-acetate (ester) and octadecanoate (salt). For the drug erythromycin estolate, estolate refers to the double salt propanoate and dodecyl sulfate.1(pp1224-1225)

In the past, some INNs included inactive components as part of their name (eg, levothyroxine sodium). The WHO modified this policy so that the INN refers to only the active component of the drug (oxacillin, ibufenac). The name that includes the salt (oxacillin sodium, ibufenac sodium) is referred to as the modified INN (INNM). However, for drugs originally named for the full entity, such as levothyroxine sodium, the shorter (active entity only) name, eg, levothyroxine, is considered the INNM.2

When a drug is referred to as a general category, the INN for the drug can be used without providing the inactive moiety.

The β-blockers most selective for β-1 activity are bisoprolol and metoprolol; acebutolol, carvedilol, and nebivolol are somewhat selective. All lose their selectivity when given at higher doses.

However, if a specific drug is discussed for a specific use, particularly when more than one formulation is available, the inactive moiety should be included with the drug name.

The patient was given erythromycin ethylsuccinate, 400 mg by mouth every 6 hours.

The inactive component should not be used when referring to an organism’s sensitivity to an antibiotic or to allergic reactions to drugs.

The strain of Streptococcus pneumoniae isolated by the laboratory was highly resistant to penicillin.

The patient’s plasma lithium level at 8 am was 2.0 mEq/L.

The woman developed urticaria after taking erythromycin.

The inactive component may also be used with the proprietary name (see 15.4.3, Proprietary Names).

Hydralazine hydrochloride was marketed as Apresoline Hydrochloride.

If both the nonproprietary name and the proprietary name are provided together, the inactive component is given only once.

The patient had been taking hydralazine (Apresoline) hydrochloride in the 1980s but developed an urticarial papular rash.

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