The proposed mechanism of action of anaesthetic medications has developed gradually since the mid-1800s when Ernst Von Bibra proposed his ‘Theory on the action of ether’. He described that inhalational anaesthetics changed 'the activity of brain cells by dissolving within the fatty component of the cell membrane. In modern times there is no agreed single mechanism of action of general anaesthetic drugs, rather that anaesthetic agents affect multiple sites and specific receptors. Ligand-gated ion channels including γ-amino butyric acid (GABA) receptors, N-methyl-D-aspartate (NMDA) receptors and voltage-gated ion channels are now proposed to be the main sites of action of anaesthetic drugs. Stimulation of inhibitory and suppression of excitatory pathways within the central nervous system forms the basis of delivery of anaesthesia.