Test 3: Local Anesthetics Specific Drugs to Know Flashcards
Which is the most widely used LA?
Lidocaine
Why has spinal use of Lidocaine declined?
Due to TNS
What does Lidocaine due to the vasculature depending on concentration?
-Vasodilates at most concentrations.
-Vasoconstricts at low doses.
Epi + Lido can prolong the DOA by as much as?
50%
Which LA is the least systemically toxic amide?
Prilocaine
Why does Prilocaine cause Methemoglobinemia?
Due to its metabolites: O-toluidine (oxidizing agent)
Can you use Mepivacaine in OB?
C/I in OB because its metabolism is prolonged in fetus and newborns.
What are the uses of Lidocaine?
-Can be used for all blocks
-Can be given topically or nebulized.
What type of molecule is Bupivacaine?
A racemic mixture
What is Bupivacaine used in?
-Regional
-Local
-Spinal
-Epidural
With Bupivacaine, ___ block outlasts ____ block.
Sensory block outlasts motor block.
How long can Bupivacaine last in a PNB vs Intrathecal?
-PNB: 12-24 hours
-SAB: 2-3 hours with 4-6 hours of analgesia
-Used with Epi
What is the biggest risk with Bupivacaine?
Can cause sudden cardiac arrest.
What concentration of Bupivacaine is C/I in OB?
0.75%
How does Ropivacaine compare to Bupivacaine?
-Structure is similar
-Ropi is a single enantiomer with less toxicity
-Can be administered in larger doses
-Less lipid soluble and less potent than Bupiv
-Vasoconstricts at low doses
Epidural use of Ropivacaine allows for what?
Sensory > Motor blockage.
Why does procaine cause allergic reactions?
Due to PABA metabolite
Which agent is the least toxic of all agents currently in use?
Chloroprocaine
-Low potency & low toxicity
-Used in high concentrations
-Rapidly metabolized
-Used in combo with longer acting LAs
When is Chloroprocaine most commonly used?
In C/S with bicarb for rapid onset of surgical block.
-Virtually no transmission to the fetus
What is important to know regarding Chloroprocaine and subsequent doses of another agent?
Chloroprocaine can interfere with subsequent doses of epidural amides or opioids.
What is unique about Tetracaine?
It is very toxic.
-Cauda Equina syndrome appears with repeated spinal dosing.
Which agent is the only natural LA?
Cocaine
What are the CV effects of Cocaine?
Inhibits the neuronal reuptake of catecholamines resulting in HTN, dysrhythmias, tachycardia, and potentially cardiac arrest.
What is the pKa of Benzocaine?
2.5 - 3.1. Very unusual.
-Almost permanently non-ionized.
-High potential for toxicity.
What are the pharmacokinetics of Benzocaine?
-A secondary amine
-Permanently non-ionized
-Slow onset
-Short DOA
It penetrates the lipid bilayer and can directly inhibit the Na v without entering the axoplasm first.
What toxicity is associated with Benzocaine?
Methemoglobinemia.
What blocks is Benzocaine used in?
Topical anesthesia only.
What is the DOA of Chloroprocaine?
Short: 15 - 30 minutes
What is the max dosing of Chloroprocaine?
-Without Epi: 11 mg/kg not to exceed 800 mg
-With Epi: 14 mg/kg not to exceed 1000 mg
What is the DOA of Lidocaine?
Medium: 30 - 60 minutes
-With Epi: 120 - 360 minutes
What is the max dosing of Lidocaine?
-Without Epi: 4.5 mg/kg not to exceed 300 mg
-With Epi: 7 mg/kg
What is the DOA of Bupivacaine?
-Long: 120 - 240 minutes
-With Epi: 180 - 420 minutes
What is the max dosing of Bupivacaine?
-Without Epi: 2 mg/kg not to exceed 175 mg
-With Epi: 2.5 mg/kg not to exceed 225 mg
What is the DOA of Ropivacaine?
Long: 120 -360 minutes
What is the max dosing of Ropivacaine?
-3 mg, not to exceed 200 mg (with or without epi)
