Benzodiazepines and use in IV sedation Flashcards
Common examples
Midazolam
Temazepam
Diazepam
Side effects of BZD
Respiratory depression
CNS depression
Muscle relaxation
Reduced BP, Increased HR = same CO
Drug interactions - opiates and alcohol
Drug interactions with BZDs
1) H2 receptor blockers and erythromycin - inhibits BZD metabolism
2) Muscle relaxants - enhanced effect
3) Antihypertensives - hypotension
4) Antipsychotics - enhanced effect
5) Antifungals - inhibit metabolism of BZDs
Mechanism of BZDs
GABA agonists
Bind to 𝛾-sub units
Alter structure of receptors
Potentiate effect of GABA - chloride ion influx
Reduced excitability and potentiation of nerve impulses
Effects of BZDs
Anxiolysis
Sedation
Anticonvulsant
Amnesiac
Muscle relaxant
As % BL
Effects of BZDs
<20% = anxiolysis
30-50% = sedation
60%+ = anaesthesia
Half life of a drug is
The time for serum concentration/metabolism of 1/2 drug
Diazepam routes of administration
Oral, IV, transmucosal
2 metabolites
Diazepam has -
half lives of each
Oxazepam 73 +/-33h
Desmethyldiazepine 6.3 +/- 1.3h
Diazepam has a rebound sedation risk of
4-6 hours after administration
Temazepam properties
Rapid acting 20-30 min
10-20mg tabs or 10mg/5ml elixir
Half life of 13 +/- 3h
Inactive metabolites
CDIII
Midazolam chemical factors
2-3x more potent than diazepam
Water soluble pH <4
Lipid soluble at body pH
Midazolam action and dosage versions
20-30s time to reach blood-brain barrier
5mg/5ml, 10mg/2ml, 10mg/5ml
Midazolam 1/2 life and metabolites
Alpha half life 15-30 mins
Beta elimination 1/2 life 1.9h +/- 0.9h
1,4-hydroxymidazolam 1.25h +/- 0.25h
Midazolam routes of admin
Oral, buccal, transmucosal, IV, rectal
Midazolam in a medical emergency
10mg buccal for epileptic seizure
Midazolam risk of rebound sedation
Only if interacting with other drugs or reversal agent
Midazolam in older people
Metabolism time increases with age
Advantages of midazolam
Fast onset
Shorter half life
Faster recovery
Less painful injection
Midazolam indications
Anxiety
ASA I-II
Overactive gag reflex
Involuntary movements e.g. cerebral palsy/Parkinsons/Tourette’s
Mild learning difficulty
Prolonged surgical procedures
Where RA is not suitable - nasal obstruction/claustrophobia
Midazolam contraindications
Uncontrolled respiratory diseases
Severe/uncontrolled comorbidities
Poor co-operation
Severe learning difficulties
BMI > 40
Pregnancy
Children < 12
Severe needle phobia
Procedure requiring more than LA
Flumazenil type of drug and chemical feature
BZD antagonist
No benzene ring
Displaces bound BZD from receptor
High affinity for receptors therefore blocks effect of BZD
Flumazenil:
Route
1/2 life - alpha and beta
Dosage
Ampules required for an IV sedation session
IV only
7-15 mins and 50-53 mins
Dose is 500 µg/5ml
200µg/15 s then 100µg/60s and observe effect up to 1g/2amps
2 ampules (1g) + spare ampule
Flumazenil risks and contraindications
Does not affect metabolism of midazolam
Short half life and risk of resedation with midazolam
Known epileptics with BZD use as may cause convulsions
Hypersensitivity to BZ as flumazenil will potentiate this
