Intravenous Hypnotic Agents: From Binding Sites to Loss of Consciousness

All the intravenous hypnotic drugs important for clinical anesthesiology reversibly unsettle functional brain networks, in order to undermine the information transfer on which consciousness depends. Three classes of intravenous hypnotic drugs are the most used nowadays: the carboxylated imidazole derivate propofol, the short-acting benzodiazepine midazolam, and the barbiturates, which show action on GABAA Receptors, potentiating gamma-aminobutyric acid (GABA) action. The dissociative agent ketamine, instead, mainly exerts its effects by reversibly blocking the activity of N-methyl-D-aspartate receptors while the most recent dexmedetomidine is an alpha-2 adrenergic receptor agonist. Nevertheless, other receptors are also involved in anesthesia determining, that is voltage-gated and ligand-gated ion channels and it is probable that each intravenous hypnotic agent alters neuronal activity acting at different levels and at multiple sites in a way not yet entirely clear.