Core Anesthesia Drugs 1: benzos, barbs, antimuscarinics Flashcards
Diazepam: class
Benzodiazepine
Diazepam: MoA
Increases the affinity for GABA at GABA receptors.
The binding of GABA to the receptor causes the opening of the Cl- channel allowing influx into the cell. Because the channel remains open, this hyperpolarizes the post synaptic membrane.
Diazepam: PK
Onset: rapid DoA: 6-8hrs 98% PB (albumin) Vd 1L/kg Highly lipid soluble E1/2t = 20-50hrs
Diazepam: metabolism
CYP450 metabolism in the liver.
3 metabolites. 1 active metabolite: desmethydiazepam = half life of 48-96hrs. Leads to hangover effect.
Metabolites excreted in the urine.
Diazepam: AE
ALL BENZOS: Decreased CBF, CMRO2 Decreased EEG Does not attenuate response to DVL Paradoxical excitement (rare) *Dose dependent resp depression Minimal decrease in SVR and increase in HR
Diazepam-specific:
Pain on injection
Fatigue, dry mouth, nausea
Diazepam: CI
Hypersensitivity Pregnancy Glaucoma Reduce dose in elderly Caution when hypoalbuminemia from hepatic or renal disease Severe hypotension
Diazepam: drug interactions
Most highly protein bound benzo
Reversal: flumazenil
Diazepam: dosing
- 3 - 0.6 mg/kg IV induction
2. 5 - 10 mg IV in 0.5-2mg increments
Midazolam: structure
Imidazole ring
Midazolam: class
Benzodiazepine
Midazolam: MoA
Increases the affinity for GABA at GABA receptors.
The binding of GABA to the receptor causes the opening of the Cl- channel allowing influx into the cell. Because the channel remains open, this hyperpolarizes the post synaptic membrane.
Midazolam: PK
Onset: 30 - 60 sec Peak: 3 - 5 min DoA: 30 - 90 mins E1/2t: 1 - 4 hrs 94% protein bound Vd: 1.5 L/kg
Midazolam: metabolism
CYP450 metabolism
Renal excretion
Midazolam: AE
ALL BENZOS: Decreased CBF, CMRO2 Decreased EEG Does not attenuate response to DVL Paradoxical excitement (rare) *Dose dependent resp depression Minimal decrease in SVR and increase in HR
Midazolam specific:
Depresses gag reflex (good for endo)
Midazolam: CI
Hypersensitivity Pregnancy glaucoma Reduce dose in elderly Caution with hypoalbuminemia in hepatic or renal pts Severe hypotension
Midazolam: drug interactions
Additive effect with opioids
Reversed with flumazenil
No hangover effect
Great for beir blocks – if local anesthetic toxicity – already have benzo on board
Midazolam: dosing
0.5 - 5mg IV
or 0.04-0.08mg/kg IV
Lorazepam: class
Benzodiazepine
Lorazepam: MoA
Increases the affinity for GABA at GABA receptors.
The binding of GABA to the receptor causes the opening of the Cl- channel allowing influx into the cell. Because the channel remains open, this hyperpolarizes the post synaptic membrane.
Lorazepam: PK
Onset: rapid 1 - 2mins DoA: 10 - 20 hrs E1/2t: 10 - 20hr 80% PB (albumin) Highly lipid soluble Vd: 1L/kg
Lorazepam: metabolism
CYP450 metabolism
Renal excretion
Lorazepam: AE
ALL BENZOS: Decreased CBF, CMRO2 Decreased EEG Does not attenuate response to DVL Paradoxical excitement (rare) *Dose dependent resp depression Minimal decrease in SVR and increase in HR
Lorazepam-specific:
Pain on injection/thrombophlebitis
Platelet aggregating inhibition (long term)
Lorazepam: CI
Hypersensitivity Pregnancy Glaucoma Reduce dose in elderly Caution with hypoalbuminemai in hepatic or renal pts Severe hypotension
Lorazepam: drug interactions
Additive effect with opioid
Reversed with FLUMAZENIL
NO hangover
Lorazepam: dosing
50 mcg/kg or 1 - 4 mg
Methohexital: class
Barbiturate
Methohexital: structure
Has a methyl radical, which contributes to convulsant activity
Methohexital: MoA
Decreases the rate of dissociation from GABA receptor. Increases duration of chloride channel remaining open and allowing Cl- to flow into the cell. This hyperpolarizes the cell and makes it more difficult to create a neuronal transmission.
Suppresses RAS and enhances sleep
↓ transmission in sympathetic ganglion
↓ post synaptic membrane sensitivity to ACh
Methohexital: PK
Onset: rapid DoA: 5-10 minutes E1/2t: 4 hrs Vd: 2L/kg Highly lipid soluble 70% PB