The first nine digits of the 15-digit BNF Code, which indicate the chemical substance under which the drug or appliance is categorised.

This is the International Non-proprietary Name (INN) and is the standard registered name for the active constituent of that medicine, for example omeprazole. For compounds the name may be more complex, such as co-magaldrox magnesium/aluminium hydrox). In some cases the name is a collective one for a range of medicines, such as alginic acid compound preparations. For prescriptions in BNF chapters 19 to 23, there is no "chemical" name, as these are dressings and appliances. Therefore, these items are reported under the BNF section name, for example, night drainage bags.