HOME

TheInfoList



OR:

In pharmacology, the international unit (IU) is a unit of measurement for the effect, not mass of a substance; the variance is based on the
biological activity In pharmacology, biological activity or pharmacological activity describes the beneficial or adverse effects of a drug on living matter. When a drug is a complex chemical mixture, this activity is exerted by the substance's active ingredient or p ...
or effect, for the purpose of easier comparison across similar ''forms'' of substances. International units are used to quantify vitamins, hormones, some
medication A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to medical diagnosis, diagnose, cure, treat, or preventive medicine, prevent disease. Drug therapy (pharmacotherapy) is an imp ...
s, vaccines,
blood product A blood product is any therapeutic substance prepared from human blood. This includes whole blood; blood components; and plasma derivatives. Whole blood is not commonly used in transfusion medicine. Blood components include: red blood cell conce ...
s, and similar biologically active substances. Many biological agents exist in different forms or preparations (e.g. vitamin A in the form of
retinol Retinol, also called vitamin A1, is a fat-soluble vitamin in the vitamin A family found in food and used as a dietary supplement. As a supplement it is used to treat and prevent vitamin A deficiency, especially that which results in xeroph ...
or ''beta''-carotene). The goal of the IU is to be able to compare these, so that different forms or preparations with the same biological effect will contain the same number of IUs. To do so, the
WHO Expert Committee on Biological Standardization WHO Expert Committee on Biological Standardization is a functioning body of World Health Organization. The Expert Committee has been meeting annually since 1947. Reports The Committee reports are published as WHO Technical Report Series. All the re ...
provides a reference preparation of the agent, arbitrarily sets the number of IUs contained in that preparation, and specifies a biological procedure to compare other preparations of the same agent to the reference preparation. Since the number of IUs contained in a new substance is arbitrarily set, there is no equivalence between IU measurements of different biological agents. For instance, one IU of vitamin E cannot be equated with one IU of vitamin A in any way, including mass or efficacy. The term ''international unit'' is also used to describe any of various physical or monetary units agreed upon internationally, in particular one forming part of the International System of Units (SI). International units as used in pharmacology are not part of the SI. The IU is distinct from the
enzyme unit The enzyme unit, or international unit for enzyme (symbol U, sometimes also IU) is a unit of enzyme's catalytic activity. 1 U (μmol/min) is defined as the amount of the enzyme that catalyzes the conversion of one micro mole of substrate per mi ...
, also known as the ''international unit of enzyme activity'' and abbreviated as U.


Equality and equivalency of IU for different substances

To define the IU for a substance, an international collaborative study is organized by the
WHO Expert Committee on Biological Standardization WHO Expert Committee on Biological Standardization is a functioning body of World Health Organization. The Expert Committee has been meeting annually since 1947. Reports The Committee reports are published as WHO Technical Report Series. All the re ...
using various assay systems in several laboratories. The main goal of the study is to reach a consensus regarding methods of analysis and the approach to standardization so that results can be compared. The study is performed using highly purified preparations of the substance, typically in lyophilized form, called "international reference preparations" or IRPs. Each preparation is divided into precisely weighed samples, with each sample stored in its own ampoule labeled with a code corresponding to the source IRP. Assays are performed using these samples and are calibrated against the previously available IU standard. These results can be quite variable; the final IU value for samples of a given IRP are determined by consensus. The IRP that provides the best results and shows the best long term stability is selected to define the next IU. This IRP is then referred to as the "international standard."


Mass equivalents of 1 IU

For some substances, the precise mass equivalent of one IU has been changed. When that happens, the former IU mass for that substance is officially abandoned in favor of a newly established mass. Such a change has happened with the immunoassay standards for
prolactin Prolactin (PRL), also known as lactotropin, is a protein best known for its role in enabling mammals to produce milk. It is influential in over 300 separate processes in various vertebrates, including humans. Prolactin is secreted from the p ...
: as one batch of standard (84/500; 53 mIU ≈ 2.5 μg) was running out of stock, a new standard (83/573; 67 mIU ≈ 3.2 μg) was calibrated against the old one (as 67.2 mIU) and replaced the former. Micronutrients: * 1 IU Vitamin A = 0.3 μg
retinol Retinol, also called vitamin A1, is a fat-soluble vitamin in the vitamin A family found in food and used as a dietary supplement. As a supplement it is used to treat and prevent vitamin A deficiency, especially that which results in xeroph ...
(~0.1 nmol) = 0.6 μg beta- carotene * 1 IU Vitamin D = 0.025 µg D2/D3 ≈ 0.65 pmol * 1 IU
Vitamin E Vitamin E is a group of eight fat soluble compounds that include four tocopherols and four tocotrienols. Vitamin E deficiency, which is rare and usually due to an underlying problem with digesting dietary fat rather than from a diet low in vit ...
= mg d- alpha-tocopherol = 0.90 mg of dl-alpha-tocopherol Peptides: * 1 IU insulin 0.0347 mg human insulin (28.8 IU/mg) * 1 IU
Oxytocin Oxytocin (Oxt or OT) is a peptide hormone and neuropeptide normally produced in the hypothalamus and released by the posterior pituitary. It plays a role in social bonding, reproduction, childbirth, and the period after childbirth. Oxytocin ...
≙ 1.68 μg of pure peptidehttps://www.nibsc.org/documents/ifu/76-575.pdf


Languages

The name ''international unit'' is often capitalized in English and other languages, although major English-language dictionaries treat it as a common noun and thus use lower case. The name has several accepted abbreviations. It is usually abbreviated as ''IU'' in English, and ''UI'' in Romance languages (for example
Spanish Spanish might refer to: * Items from or related to Spain: **Spaniards are a nation and ethnic group indigenous to Spain **Spanish language, spoken in Spain and many Latin American countries **Spanish cuisine Other places * Spanish, Ontario, Can ...
''unidad internacional'', French ''unité internationale'',
Italian Italian(s) may refer to: * Anything of, from, or related to the people of Italy over the centuries ** Italians, an ethnic group or simply a citizen of the Italian Republic or Italian Kingdom ** Italian language, a Romance language *** Regional It ...
''unità internazionale'',
Romanian Romanian may refer to: *anything of, from, or related to the country and nation of Romania ** Romanians, an ethnic group **Romanian language, a Romance language ***Romanian dialects, variants of the Romanian language **Romanian cuisine, traditiona ...
''unitate internațională''), ''IE'' in several Germanic languages (for example
German German(s) may refer to: * Germany (of or related to) **Germania (historical use) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizens of Germany, see also German nationality law **Ge ...
''internationale Einheit'', Dutch ''internationale eenheid'') or as other forms (for example
Russian Russian(s) refers to anything related to Russia, including: *Russians (, ''russkiye''), an ethnic group of the East Slavic peoples, primarily living in Russia and neighboring countries * Rossiyane (), Russian language term for all citizens and p ...
МЕ, международная единица 'mezhdunarodnaya yedinitsa'' Hungarian NE, ''nemzetközi egység''). In order to remove the possibility of having the letter "I" confused with the digit "1", some hospitals have it as a stated policy omit the "I", that is, to only use U or E when talking and writing about dosages, while other hospitals require the word "units" (or words "international units") to be written out entirely. (For example, "three international units per litre" may be abbreviated "3 U/L". The "liter" sign (L) is less affected, as less confusing written forms are used.)


See also

* '' United States Pharmacopeia'' (''USP'')


References


Notes


Citations


External links


WHO reference preparations

Online converter with authoritative references for all substances
{{DEFAULTSORT:International Unit Units of measurement Dosage forms