Benzodiazepine

BENZODIAZEPINE


CLASSIFICATION:

  • Long Acting
    • Flurazepam 50-100 t1/2(hrs)
    • Diazepam 30-60 t1/2(hrs)
    • Nitrazepam 30 t1/2(hrs)
    • Flunitrazepam 15-25 t1/2(hrs)
  •  Short-Acting 
    • Temazepam with t1/2 8-12 hrs
      • Benzodiazepine without anticonvulsant property.
    •  Triazolam with t1/2 2-3 hrs
    •  Midazolam 2 t1/2(hrs)
    • Alprazolam 

MOA:

PHARMACOKINETICS:

  • Short-acting BZDs:
  • Eg: Midazolam – IV or IM as an induction agent.
    • Rapid onset of action.
    • Quick drug clearance.
    • Causes anterograde amnesia, tachyphylaxis during high dose infusions.
    • Decreased cardiovascular effects as compared to propofol 
  • Temazepam or oxazepam – Revives insomnia. 
    • At lower doses, relieves acute symptoms of anxiety, such as panic attacks & phobias.
  • Long-acting BZDs: 
    • Slower onset of action following oral administration → Hence prolonged pharmacological action.
    • Sedation.
    • Prevents increased muscle tone of tetanus infection. 
  • Metabolized in liver by dealkylation and hydroxylation.
  • Excreted in urine as glucuronide conjugates.

ACTIONS:

  • Antianxiety
  • Sedation: 
    • Increasing dosage produce sleep & hence considerable as hypnotic
    • I.V administration used extensively to produce conscious sedation during unpleasant procedures. 
    • Eg: Diazepam & midazolam.
    • Cardiovascular stability – IV diazepam 
    • Midazolam potentiates propofol in co-induction technique.
  • Anticonvulsants: 
    • Clonazepam & diazepam – Effective in status epilepticus.
  • Muscle relaxation: 
    • Reduce muscle tone.
  •  Amnesia: 
    • IV benzodiazepines produces antegrade amnesia. 
    • Midazolam – Very intense for 20-30 minutes
    • Lorazepam – Longer amnesia – 6 hr.

DRUGS:

  • Inverse agonist of benzodiazepine receptor – Beta carboline.
  • Benzodiazepine antagonist – Flumazenil

USES:

  • As hypnotic –
    • Daytime sedation (Alprazolam)
  • As anxiolytic.
  • Antidepressant  (Alprazolam)
  • As anticonvulsants, especially emergency control of status epilepticus  
    • To avoid future recurrence of seizure attacks Oral Diazepam 6 hourly is given.
  • As centrally acting muscle relaxant.
  • For anesthetic medication and IV anesthesia 
  • Alcohol withdrawal in dependent subjects 
  • Mostly given along with analgesics (NSAIDs|). 
  • DOC in elderly & with liver disease.
    • Lorazepam, OxazepamTemazepam
  • Spasmolytics.
  • Anti-ulcer.

ADVERSE EFFECT:

  • Dizziness, lassitude, vertigo, disorientation, amnesia, increased reaction time with motor incoordination, impairment of mental coordination occur. 
  • Weakness, blurring of vision, dry mouth and urinary incontinence.
  • BZD poisoning:
    • Benzodiazepine antagonist -Flumazenil
    • Eg: Diazepam poisoning.
  • Paradoxical stimulation, irritability, and sweating may occur with flurazepam.
  • Increase in nightmares and behavioral alterations 
  • Increased psychological effects with usage of short-acting benzodiazepines in insomnia. 
  • Disturbed REM sleep patterns.

Exam Important

  • Diazepam poisoning is treated by Flumazenil
  • Benzodiazepine antagonist  Flumazenil
  • Benzodiazepines of choice in elderly and those with liver disease Lorazepam, Orazepam & Temazepam
  • Shortest acting benzodiazepine is Triazolam
  • Benzodiazepine without anticonvulsant property is Temazepam
  • To avoid future recurrence of seizure attacks Oral Diazepam 6 hourly is given
  • Alprazolam is an anxiolytic benzodiazepine with  antidepressant  action
  • IV diazepam  shows Coronary dilatation
  • Inverse agonist of benzodiazepine receptor is Beta carboline
  • Midazolam causes  Anterograde amnesia, tachyphylaxis during high dose infusions & Decreased cardiovascular effects as compared to propofol
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