Midazolam

Question 1

What type of medication is midazolam?

Answer 1

A Benzodiazepine

Question 2

What is the mechanism of action of Midazolam?

Answer 2

Midazolam is an anticonvulsant with anxiolytic and amnesic effects

• Midazolam is a short acting benzodiazepine that binds to the benzodiazepine site on GABA-A receptor sites on post-synaptic neurons.
• This increases the affinity of GABA for the GABA receptor.
• GABA: Gamma-Aminobutyric Acid, an inhibitory neurotransmitter.
• (inhibitory neurotransmitter gamma-aminobutyric acid)
• Midazolam increases chloride entry into cells
• The increased chloride levels cause the cell to be hyperpolarised (away from the threshold)
• This increases neuroinhibition (cell less excitable)

These receptors have been identified in different body tissues including the heart and skeletal muscle, although mainly appear to be present in the central nervous system.

Question 3

What are the different routes, and associated onsets, peaks and durations of midazolam?

Answer 3

• Route: IM
  
  • Onset: 5 - 10 min
  • Peak: 15 min
  • Duration: 30 min
• Route: IV
  
  • Onset: 1 - 3 min
  • Peak: 10 min
  • Duration: 20 min
• Route: IN
  
  • Onset: 1 - 3 min
  • Peak: 12 min
  • Duration: 20 min

Question 4

What are the adverse effects of midazolam?

Answer 4

• Decreased LOC resulting in upper airway obstruction
• Respiratory and cardiovascular depression which may be exacerbated in patients with limited physiological reserves and/or under the influence of alcohol or drugs

Question 5

What are the contraindications for midazolam?

Answer 5

Nil for NSW Ambulance

Question 6

What are the preparations and dosages for midazolam for seizures?

Answer 6

• Preparation: 5mg (1mL) ampoule
• Dilution 5mg (1mL) diluted with 4mL NaCl to a total volume of 5mL(1mg:1mL)
• Seizures
  
  • <16yo:
    
    • IV/IO: 0.15mg/kg diluted bolus (max 2.5mg)
      
      • Repeat: 5min
      • Max Total Dose: 0.45mg/kg (up to 15mg)
    • IM: 0.15mg/kg undiluted bolus (max 5mg)
      
      • Repeat: 5min
      • Max Total Dose: 0.45mg/kg (up to 15mg)
    • IN: 0.3mg/kg undiluted bolus via MAD (max 5mg)
      
      • Repeat: Nil
      • Max Total Dose: 0.3mg/kg (up to 5mg)
  • 16yo+:
    
    • IV: 2.5mg diluted slow bolus
      
      • Repeat: 5min
      • Max Total Dose: 15mg
    • IM: 5mg undiluted bolus
      
      • Repeat: 5min
      • Max Total Dose: 15mg

Question 7

What are the preparations and dosages of midazolam for behavioural disturbance?

Answer 7

• Preparation: 5mg (1mL) ampoule
• Dilution 5mg (1mL) diluted with 4mL NaCl to a total volume of 5mL(1mg:1mL)
• Dose
  
  • <14yo:
    
    • IV: 0.15mg/kg diluted slow bolus (max 2.5mg)
      
      • Repeat: 3min
      • Max Total Dose: 0.45mg.kg (up to 15mg)
    • IM: 0.15mg/kg undiluted bolus (max bolus 5mg)
      
      • Repeat: 5min
      • Max Total Dose: 0.45mg/kg (up to 15mg)
  • 14 - <65yo:
    
    • IV: 2.5mg diluted slow bolus
      
      • Repeat: 3min
      • Max Total Dose: 15mg
    • IM: 5mg undiluted bolus
      
      • Repeat: 5min
      • Max Total Dose: 15mg
  • 65+yo:
    
    • IV: 1.25mg diluted slow bolus
      
      • Repeat: 5min
      • Max Total Dose: 7.5mg
    • IM: 2.5 - 5mg undiluted bolus
      
      • Repeat: 5min
      • Max Total Dose: 7.5mg

Note: Paramedi s are authorised (if indicated) to administer a single dose of midazolam in between the initial and repeat dose of droperidol under protocols M28 and MH6 ONLY if the patient is physically aggressive.