Bring the known number of international units (IU) to milligrams first - in these units is most often measured amount of a substance in pharmacology. Since this value depends on what the substance of the Committee's list of biological standardization you are interested in, you have to find a weight proportion set him, in the documents of the organization on its website - http://www.who.int/bloodproducts/catalogue/en/index.html.
There is a possibility to entrust the conversion international units to milligrams any online service. For example, which is placed on the page http://www.uapf.com.ua/iu.php. Going to the online Converter, enter a value in ME field "Size" and then select in the drop-down list placed in the column "Substance", the name of your drug. After clicking on "Convert" script, posted on this page, will produce the calculations and display the result. It can look like this: "Capreomycin 100 IU (IU) = 0.10870 mg (mg)".
Convert the resulting value from milligrams to milliliters. In milliliters is measured by the volume of the substance, which depends on its density and concentration. To know the matching weight and volume for a particular drug can be from the appropriate labels on its packaging. If you don't see, it is better to consult in any medical facility.
Multiply the obtained in the second step, the value in milligrams per defined in the third step, the correspondence between weight and volume measures of the desired substance. It is possible to use the standard calculator software of the Windows operating system which is started by pressing shortcut keys win + r followed by typing calc and pressing Enter.