New drugs--boon or bane? Premedication and intravenous induction agents.

Research on the benzodiazepines has shown that they have certain advantages over the opiates as premedicants. Diazepam, which produces good tranquilization, is well absorbed when given orally though absorption is influenced by other drugs given at the same time. Oral lorazepam leads to more prolonged sedation and amnesia but the final elimination is more rapid. Several new intravenous anaesthetics have been introduced during the last five years but none seems likely to replace thiopental. The theoretical disadvantages of thiopental are offset by its water-solubility, and the use of Cremophor EL in preparations of propanidid, alphaxalone, di-isopropyl phenol and one preparation of diazepam has led to many hypersensitivity reactions. Ketamine is gradually finding its rightful place in anaesthesia but its use is becoming limited to anaesthesia in difficult circumstances. The future concomitant use of other drugs and separation of isomers of ketamine may again broaden its applications. The new water-soluble steroid minaxolone has its own disadvantages, and the water-soluble benzodiazepine midazolam is as unpredictable for induction of anaesthesia as diazepam.