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
Methohexital: metabolism
Hepatic metabolism
Renal/fecal elimination
Methohexital: AE
*Induces seizures
*Myoclonus
*Hiccups/cough/laryngospasm
Reflex tachycardia
Decreased CBF, ICP and CMRO2
Histamine release
Dose dependent resp depression
Pain on injection
Decreased threshold for pain
CYP450 inducer
Methohexital: CI
Seizure history
Pregnancy
Porphyria!
Asthma
Methohexital: drug interactions
CYP450 inducer; may need frequent NMB redosing
Will precipitate in LR
Methohexital: dosing
1 - 2 mg/kg IV
Thiopental: class
Barbiturate
Thiopental: structure
Sulfur at carbon #2
Thiopental: 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
Thiopental: PK
Onset: rapid E1/2t: 12 hrs Vd: 2.5 L/kg Highly lipid soluble 80% PB (albumin)
Thiopental: metabolism
CYP450 to hydroxythipental (10-20%).
Metabolites excreted in urine.
Thiopental: AE
Reflex tachycardia Decreased CBF, ICP and CMRO2 Isoelectric EEG Histamine release Dose dependent resp depression Pain on injection Decreased threshold for pain N/V
Thiopental: CI
Pregnancy
Porphyria
Asthma
Thiopental: drug interactions
CYP450 inducer; expect increased NMB redosing
Decrease dose 30% in 1st trimester, elderly
Thiopental: dosing
3 - 5mg/kg IV
Phenobarbital: class
Barbiturate
Phenobarbital: structure
Phenyl group at carbon #5
Phenobarbital: 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
Causes drowsiness and decreases motor activity
Phenobarbital: PK
*Onset: 5 mins
*Peak: 30 mins
*DoA: 4 - 10 hrs
*E1/2t: 54 - 170 hrs
40% PB
Phenobarbital: metabolism
CYP450 metabolism with 60% unchanged in urine
Phenobarbital: AE
Reflex tachycardia Decreased CBF, ICP and CMRO2, isoelectric EEG Dose dependent resp depression Pain on injection Decreased threshold for pain N/V
Specific to phenobarb:
Bone marrow suppression
Agranulocytosis, thrombocytopenia, megaloblastic anemia
Hepatotoxicity
Stevens Johnson syndrome
Ataxia
**Intra arterial injection can cause loss of limb.
Phenobarbital: CI
Severe liver disease
Porphyria
Pregnancy
Phenobarbital: drug interactions
STRONG CYP450 inducer!!
Will precipitate in LR
Phenobarbital: dosing
10-20 mg/kg
Then 5 mg/kg q 15-30mins until seizure controlled
Max of 30 mg/kg
Atropine: class
Tertiary amine muscarinic receptor antagonist
Atropine: MoA
Competitively and reversibly bind to muscarinic receptors to inhibit binding of Ach allowing sympathetic response to dominate
Antagonizes histamine and serotonin
Atropine: PK
Onset: 1 min DOA: 30 - 60 mins E1/2t: 2-3 hrs Vd: 1.5L/kg Highly lipid soluble 40% PB
Atropine: metabolism
Hepatic metabolism
18% unchanged in the urine
Atropine: AE
Blurry vision Pupillary dilation ↑ IOP Delirium Sedation/hallucinations/disorientation Dry mouth Increased HR and CO Urinary retention and constipation
Atropine: CI
Glaucoma CAD Pheochromocytoma Thyrotoxicosis Hyperpyrexia Mobitz II GI obstruction AchE therapy
Atropine: dosing
Bradycardia: 0.4 - 1 mg IV
Reversal for edrophonium: 0.01 mg/kg IV
Resuscitation: 1 mg IV up to 3 mg
Scopolamine: class
Tertiary amine muscarinic receptor antagonist
Scopolamine: MoA
Competitively and reversibly bind to muscarinic receptors to inhibit binding of Ach, preventing the action on parasympathetic systems and allowing sympathetic response to dominate
Scopolamine: PK
Onset: 10 mins DOA: 2 hrs E1/2t: 4.8 hrs (3-7 days for full recovery) Vd: crosses BBB, placenta PB: reversibly binds, % unknown
Scopolamine: metabolism
Hepatic metabolism
Renal excretion
Scopolamine: AE
*Sedation and weakness V-fib Increased HR Orthostatic hypotension Delayed awakening Increased IOP Blurry vision Dry mouth and constipation
Scopolamine: CI
Hypersensitivity Liver disease AMS Glaucoma CAD Pheochromocytoma Thryotoxicosis Myasthenia gravis
Scopolamine: dosing
0.3-0.6mg IV Q4-6 hours
Glycopyrrolate: class
Quaternary amine muscarinic receptor antagonist
Glycopyrrolate: MoA
Reversible competitive blockade of Ach at muscarinic receptors. Allows sympathetic response to dominate.
Glycopyrrolate: PK
Onset = 3-5mins
DOA = 2-4 hrs
E1/2 t = 1.5hrs
Vd = 0.4L/kg
Glycopyrrolate: metabolism
Hepatic metabolism with 85% unchanged in the urine
Glycopyrrolate: AE
Blurred vision Dry mouth PVC and tachycardia Dysrhythmias N/V Ileus and constipation **Malignant hyperthermia Headache
Glycopyrrolate: CI
Hypersensitivity Infants CAD Renal disease! Hyperthyroid Hx of MH Pheochromocytoma
Glycopyrrolate: dosing
Antisialagogue or bradycardia: 0.1 - 0.2 mg IV
Reversal with neostigmine: 0.01 mg/kg IV