Glass phial of British Standard penicillin, 1946. British Standard penicillin was defined as one milligram of penicillin containing 1,600 International Units. An International Unit is defined as the potency or activity of a drug. The standard was set by the National Institute for Medical Research. International Standards were set in 1944 and in 1952. Standardization of drugs such as penicillin is important to ensure the quantity and quality produced and given to patients is consistent all over the world. Penicillin was discovered in 1928 by Scottish scientist Alexander Fleming. People began using it to treat infections in 1942 and it saved the lives of many soldiers during the Second World War.