Cardboard tube containing glass phial of British Standard Penicillin, dated 27.4.46, by the National Institute for Medical Research, London, British

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. Standardisation of drugs such as penicillin is important to ensure the quantity and quality produced and given to patients is consistent all over the world.