Midazolam (Dormicum)
Mechanism of action
Benzodiazepine and anticonvulsant.
Acts on benzodiazepine receptor via GABA-A receptor and enhances its inhibitory effect through increased frequency of chloride channel opening.
Dose-related effect. Causes sedation, anxiolysis, anterograde amnesia, muscle relaxation and has an anticonvulsant effect. At higher doses causes cardiorespiratory depression.
Indications and dose
Side-effects
Vomiting
Respiratory depression
Confusion
Drowsiness; excess sedation
Paradoxical agitation (more common in elderly)
Cardiovascular depression
Precautions
Metabolised by liver - may need reduced dose in liver failure.
Additive effects with other CNS depressant drugs.
Respiratory and cardiovascular depression can be more profound in cardiopulmonary disease.
Pharmacokinetics
Onset of action: Intravenous peak 3-5 minutes; Intramuscular peak 30-60 minutes
Duration of action: Intramuscular: mean 2 hours; Intravenous bolus: <2 hours
Bioavailability: Oral: 40-50%; Intramuscular: >90%
Distribution: widely distributed in body including CSF; 97% protein bound
Metabolism: Hepatic
Half-life of elimination: 3 hours
Excretion: Urine
Reversal agent
Flumazenil - benzodiazepine antagonist
Directions for administration
Dilute in 5% glucose or 0.9% sodium chloride
Medicinal forms
Oromucosal solution
Solution for injection
Solution for infusion
NB: high-strength ampoules (5 mg/ml or 2 mg/ml) and normal strength ampoules (1 mg/ml)
