Contraindication A reason not to give a specific drug due to something in the patient’s history.344 Drug Chemical substances which interact with biological systems. Excretion Removal out of the body. First pass metabolism The amount of drug which is metabolise by the liver before reaching general circulation. Half life The time taken for plasma concentration to reduce by a half of its original value. Inhalation Breathing in. Intramuscular Into a muscle. Licensed A marketing authorisation. Medicines management The clinical, cost effective and safe use of medicines to ensure patients get the maximum benefit from the medicines they need, while at the same time minimising potential harm.