Midazolam as an intravenous induction agent

The influence of age on the onset of anaesthesia with midazolam

There was a considerable individual variation in response to a standard induction dose of 0.3 mg/kg midazolam in unpremedicated patients. This is shown by variations in time to onset of sleep and the fact that about one quarter of subjects did not lose consciousness in 3 minutes. In 166 fit patients a good negative correlation was demonstrated between the age of the patients and time to loss of consciousness. Patients over 50 years differed from younger patients in a greater reliability of effect and significantly shorter induction time. In elderly patients midazolam is a more reliable induction agent than in the young.

Midazolam. A review of its pharmacological properties and therapeutic use

Midazolam is a short-acting water-soluble benzodiazepine (at pH less than 4), a member of a new class of imidazobenzodiazepine derivatives. At physiological pH the drug becomes much more lipid soluble. Water solubility minimises pain on injection and venous thrombosis compared with diazepam administered in organic solvent. Midazolam is a hypnotic-sedative drug with anxiolytic and marked amnestic properties. To date it has been used mostly by the intravenous route, for sedation in dentistry and endoscopic procedures and as an adjunct to local anaesthetic techniques. It has proved less reliable than thiopentone, but preferable to diazepam, as an intravenous induction agent and is unlikely to replace the other well established drugs. However, due to the cardiorespiratory stability following its administration, midazolam is useful for anaesthetic induction in poor-risk, elderly and cardiac patients. The short elimination half-life (1.5-3.5h) and the absence of clinically important long acting metabolites make midazolam suitable for long term infusion as a sedative and amnestic for intensive care, but clinical trials have yet to be completed. Thus, a combination of properties make midazolam a useful addition to the benzodiazepine group.