International unit

An international unit ( IU , sometimes - a unit of action, AU ^{[1] [2]} ) - in pharmacology is a unit of measure for a dose of a substance , based on its biological activity. Used for vitamins , hormones , certain drugs, vaccines , blood components and similar biologically active substances.

Despite its name, IU is not part of an international measurement system . The amounts of a substance in 1 IU for different classes of substances are completely different. Units of action, ED , most often coincide with IU.

The exact definition of a single IU is different for different substances and is established by international agreement. The Biological Standardization Committee of the World Health Organization provides reference preparations of certain substances, (arbitrarily) sets the number of IU units contained in them, and determines biological procedures for comparing other preparations with reference ones. The purpose of such procedures is that different blanks with the same biological activity contain an equal number of IU units.

For some substances, mass equivalents of one IU were established over time, and measurements in these units were sometimes refused. However, units of IU even in this case may remain in widespread use due to convenience. For example, vitamin E exists in eight different forms, distinguished by its biological activity. Instead of specifying the type and weight of the vitamin in the workpiece, it is sometimes convenient to simply indicate its quantity in IU. The same applies to other vitamins , insulin, etc.

Mass equivalents of 1 IU for some classes of substances:

• 1 IU of vitamin A : the biological equivalent of 0.3 µg retinol , or 0.6 µg β- carotene
• 1 IU of vitamin C : 50 µg of ascorbic acid
• 1 IU of vitamin D : the biological equivalent of 0.025 μg of chole- or ergocalciferol
• 1 IU of vitamin E : the biological equivalent of 2/3 mg of d-α- tocopherol or 1 mg of dl-α-tocopherol acetate
• 1 IU of insulin preparations: the biological equivalent of 34.7 µg of human insulin (28.8 IU / mg).

In the documents of different countries, the designation is localized in the language of the country, as in Russian. In English, it is often referred to as IU (from the International unit), in many Romance languages ​​UI (for example, in Spanish it is from unidad internacional, in French - from unité internationale, in Italian - from unità internazionale, in Romanian - from unitate internațională), IE in some Germanic languages ​​(for example, in German - from internationale Einheit, by the Datta - from internationale eenheid). There are other options, such as the Hungarian NE (nemzetközi egység). In order not to confuse the letter “I” with the number “1”, many foreign medical organizations avoid using the letter “I” and use one letter U or E to designate a unit of measurement (for example, “three international units per liter” can be recorded as “3 U / L”), while others prefer to write the entire name. In addition, derivative units are practiced, which are also recorded differently - the concentration of ME / ml is sometimes replaced by KME / l or kE / l (kilo-units per liter, which is exactly the same as units per milliliter), and sometimes and with additional postscripts, which further confuses the picture. For example, in the results of a specific ImmunoCAP alert, they write KUA / L, where the record is kU _A / l, and the index A means that the measurement is allergen specific. ^[3]