Benzodiazepines
Drugs in
Long-acting
- diazepam
- chlordiazepoxide
- nitrazepam
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Short-acting
- lorazepam
- oxazepam
- temazepam
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Features
- anxiolytic
- sleep inducing
- anticonvulsant
- muscle relaxants
Indications
- SHORT TERM USE ONLY
- insomnia
- generalised
anxiety (not phobic)
- Panic attacks
- Anterograde amnesia in procedures such as endoscopy (high dose)
- Tetanus
- Reduction muscle spasm due to pain
- alcohol withdrawal states
- control of violent behaviour
- Emergency Tx status epilepticus
- second-line treatments in refractory epilepsy
- Febrile convulsions
Mechanism of action
- potentiation of GABA inhibitory effects
Pharmacokinetics
- Absorption oral>I.M
- Produce active metabolites with longerT1/2 e.g (T1/2 20-80hrs,
N-desmethyl metabolite T1/2 200hrs)
- Highly bound to protein in plasma
- Metabolised in the liver, but weak microsomal enzyme inducers
- Age influenced elimination (except oxazepam)
- Slow withdrawal of BDZ needed
Side-effects
- drowsiness
- sedation
- ataxia
- respiratory depression
- disinhibition (possibly leading to aggression)
- tolerance
- withdrawal syndrome
- marked anxiety
- shakiness
- abdominal cramps
- perceptual disturbances
- persecutory delusions
- fits
- Sedation - drowsiness & lightheadedness
- CNS depression - ataxia & confusion
- Dependence with long-term (>2wk) use
- Withdrawal syndrome
- Hangover with continuous administration
- Hypnotics at high dose
Contra-indications
- Respiratory depression
- Muscle weakness
- Severe hepatic impairment
- in liver impairment prefer shorter T1/2
- Not used alone in depression
- alcohol potentiates effects
Interactions
- With other centrally acting drugs
- Inhibition BDZ by cimetidine and omeprazole
- Opioid analgesics
- Antibacterials
- e.g. isoniazid inhibits metabolism diazepam
- Antiepileptics e.g. phenytoin
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