![radiance_multivitamins_nutritional_information_crop](https://upload.wikimedia.org/wikipedia/commons/6/62/Radiance_multivitamins_nutritional_information_crop.jpg)
In
pharmacology
Pharmacology is a branch of medicine, biology and pharmaceutical sciences concerned with drug or medication action, where a drug may be defined as any artificial, natural, or endogenous (from within the body) molecule which exerts a biochemica ...
, 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 ...
or effect, for the purpose of easier comparison across similar ''forms'' of substances. International units are used to quantify
vitamin
A vitamin is an organic molecule (or a set of molecules closely related chemically, i.e. vitamers) that is an Nutrient#Essential nutrients, essential micronutrient that an organism needs in small quantities for the proper functioning of its ...
s,
hormone
A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are required ...
s, some
medication
A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy (pharmacotherapy) is an important part of the medical field and re ...
s,
vaccine
A vaccine is a biological Dosage form, preparation that provides active acquired immunity to a particular infectious disease, infectious or cancer, malignant disease. The safety and effectiveness of vaccines has been widely studied and verifie ...
s,
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 concen ...
s, and similar biologically active substances.
Many biological agents exist in different forms or preparations (e.g.
vitamin A
Vitamin A is a fat-soluble vitamin and an essential nutrient for humans. It is a group of organic compounds that includes retinol, retinal (also known as retinaldehyde), retinoic acid, and several provitamin A carotenoids (most notably bet ...
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 xerophtha ...
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
Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different elementar ...
or
efficacy
Efficacy is the ability to perform a task to a satisfactory or expected degree. The word comes from the same roots as ''effectiveness'', and it has often been used synonymously, although in pharmacology a pragmatic clinical trial#Efficacy versu ...
.
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
The International System of Units, known by the international abbreviation SI in all languages and sometimes pleonastically as the SI system, is the modern form of the metric system and the world's most widely used system of measurement. E ...
(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 micromole 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
Substance may refer to:
* Matter, anything that has mass and takes up space
Chemistry
* Chemical substance, a material with a definite chemical composition
* Drug substance
** Substance abuse, drug-related healthcare and social policy diagnosis ...
, typically in lyophilize
Freeze drying, also known as lyophilization or cryodesiccation, is a low temperature dehydration process that involves freezing the product and lowering pressure, removing the ice by sublimation. This is in contrast to dehydration by most conve ...
d 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 pit ...
: 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
Vitamin A is a fat-soluble vitamin and an essential nutrient for humans. It is a group of organic compounds that includes retinol, retinal (also known as retinaldehyde), retinoic acid, and several provitamin A carotenoids (most notably bet ...
= 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 xerophtha ...
(~0.1 nmol) = 0.6 μg beta-carotene
The term carotene (also carotin, from the Latin ''carota'', "carrot") is used for many related unsaturated hydrocarbon substances having the formula C40Hx, which are synthesized by plants but in general cannot be made by animals (with the exc ...
[
* 1 IU ]Vitamin D
Vitamin D is a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and many other biological effects. In humans, the most important compounds in this group are vitamin D3 (c ...
= 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 vitami ...
= mg d- alpha-tocopherol = 0.90 mg of dl-alpha-tocopherol
Peptides:
* 1 IU insulin
Insulin (, from Latin ''insula'', 'island') is a peptide hormone produced by beta cells of the pancreatic islets encoded in humans by the ''INS'' gene. It is considered to be the main anabolic hormone of the body. It regulates the metabolism o ...
≙
In mathematics, a binary relation associates elements of one set, called the ''domain'', with elements of another set, called the ''codomain''. A binary relation over sets and is a new set of ordered pairs consisting of elements in and ...
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 peptide[https://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
The Romance languages, sometimes referred to as Latin languages or Neo-Latin languages, are the various modern languages that evolved from Vulgar Latin. They are the only extant subgroup of the Italic languages in the Indo-European language fam ...
(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, Cana ...
''unidad internacional'', French
French (french: français(e), link=no) may refer to:
* Something of, from, or related to France
** French language, which originated in France, and its various dialects and accents
** French people, a nation and ethnic group identified with Franc ...
''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 Ita ...
''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, traditional ...
''unitate internațională''), ''IE'' in several Germanic languages
The Germanic languages are a branch of the Indo-European language family spoken natively by a population of about 515 million people mainly in Europe, North America, Oceania and Southern Africa. The most widely spoken Germanic language, Engli ...
(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
**Ger ...
''internationale Einheit'', Dutch
Dutch commonly refers to:
* Something of, from, or related to the Netherlands
* Dutch people ()
* Dutch language ()
Dutch may also refer to:
Places
* Dutch, West Virginia, a community in the United States
* Pennsylvania Dutch Country
People E ...
''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 peo ...
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
The ''United States Pharmacopeia'' (''USP'') is a pharmacopeia (compendium of drug information) for the United States published annually by the United States Pharmacopeial Convention (usually also called the USP), a nonprofit organization that ...
'' (''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