Introduction

• A water-soluble benzodiazepine that has anxiolytic, sedative and anticonvulsive characteristics. These are based on its bond with receptors in the central nervous system; its action to increase the inhibitory effect of the g-aminobutyric acid (GABA) neurotransmitter on the GABA receptors and subsequent membrane threshold.
• Midazolam is lipid-soluble in physiological pH and it reaches the central nervous system quickly.

Pharmacokinetics

Onset

• Rapid onset

Absorption

• Aafter IM injection, absorption from the muscle tissue is rapid and complete. Maximum plasma concentrations are reached within 30 minutes. The absolute bioavailability after IM injections is over 90%.

Excretion

• 60-80% of the dose is excreted in urine as conjugates

Pharmacodynamics

Desired Effects

• Midazolam is a very short-acting benzodiazepine, with powerful anxiolytic, sedative-hypnotic and muscle relaxant effects caused by facilitation of GABA-mediated CNS inhibitory pathways.
• It has rapid onset of actions and, because of rapid metabolic transformation, short duration.

Side Effects

• Respiratory depression.
• Hypotension.
• Anterograde and retrograde amnesia.

Duration of Action:

• Very short acting.

Half-life

• 1 to 3 hours

Other Drug Interactions

• Midazolam has additive CNS-depressant effects with all other CNS depressants.