Benzodiazepine Flashcards
All Benzos are great for: (5)
Anxiolysis Sedation Anterograde Amnesia Anticonvulsant Muscle Relaxation (spinal level)
MOA: Benzos
Mechanism of action:
Benzos work by increasing the affinity of the GabaA receptor for GABA.
They do not activate GABA.
Structure of Benzos
Benzene ring fused with
7 member diazpine ring
In general, Benzos are
_______ lipid soluble
_______ protein bound
HIGHLY lipid soluble and
HIGHLY protein bound
short duration in versed is attributed to
HIGH LIPOPHILICITY, it redistributes, effect goes down.
Effect site equilibration time of versed
0.9 - 5.6 minutes
Midazolam: active metabolites
- = 1-hydroxy-midazolam
1-hydroxy-midazolam + kidneys
active metabolite of versed
may build in up in patients with renal insufficiency if on high doses of continuous IV versed
metabolism of versed is slowed with medications:
cimetidine, erythryomycine, calcium channel blockers, anti fungal drugs,)
Benzos + EEGs
Benzos are not potent enough to produce a flat line EEG
Benzos + swallowing reflex
will reflex decrease swallowing reflex, can’t cough properly.
Benzodiazepines + opiods
analgesic effects of opioids are reduced with Benzos
hypo ventilatory and hypoxemia synergistic effect with benzos
CV effects of midazolam
decreased SVR at induction dose
BP consequently decreases
CO unchanged.
Doesn’t prevent hR/BP changes with intubation
DOSES FOR VERSED
premedication/pediatrics: 0.25-.5 mg/kg PO
Max PO dose for peds: 20 mg
IV sedation/adults: 1 - 2.5 mg IV can give as high as 5 mg PRN
Induction dose: 0.1 -0.2 mg /kg over 30 - 60 sec
Maintenance: incremental or infusion
Diazepam: CV effects
minimal changes in SVR, CO, BP, <20%.
Good for CV patients
Diazepam is differentiated by
its prolonged duration of action , e1/2 t = 21-37 hours
Diazepam metabolites:
3!
desmethyldiazepam = active
oxazepam/temazepam = NA
Diazepam is rapidly absorbed from
GI tract
less first pass effect than versed
desmethyldiazepam
active metabaolite
e1/2 time = 48 - 96 hrs
Diazepam doses:
pre-medicaiton/oral: 10-15 mg
pre-medicaition/IV: 0.2 mg/kg (reduces MAC)
induction: 0.5 - 1 mg/kg IV
anticonvulsant: inhibit activity in hippocampus & limbic system; 0.1 mg/kg IV
metabolism of diazepam is affected by
drugs that inhibit CYP450 i.e. cimetidine
metabolism will be slowed.
flumazenil (romazicon) MOA:
competitive antagonist for benzo binding site, has high affinity, can knock Benzos off
lorazepam: notable attribuets
5-10x potency of diazepam
metabolites are pharmacologically inactive
SLOW onset, peaks at 2 hours [[peak plasma]]
Doses of lorazepam:
premedication/PO: 50 mcg/kg
Max dose: 4 mg
flumazenil DOA:
30- 60 minutes.
Flumazenil peaks in:
2 minutes. Must wake 2 minutes before next dose
Flumazenil dose:
0.2 mg IV initial
repeat dose : 0.1 mg IV
MAX DOSE: 3 mg in 24 hr period
infusion: 0.1 - 0.4 mg/hr
0. 5 - 1 mc/kg/min
In differential diagnosis of coma can give up flumazenil up to
5 mg
comparative elimination half times for benzos
midazolam < lorazepam < diazapam
