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Flashcards in Local Anesthetics Deck (35):
1

What is the MOA/ pharmacodynamics of Bupivicane?

  • Blocks Na+ channels in nerve cells while in the closed/ inactive state preventing depolarization and impulse transmission
  • Holds the nerve under threshold, thereby decreasing the chance of action potential

2

What is the drug class/ chemical structure of Bupivicaine?

  • Bupivacaine is an aminoamide local anesthetic
  • Bupivacaine is a Pipecoloxylidide.
  • Adding a butyl group to a Mepivicaine makes Bupivacaine and makes it 35x more lipid soluble (potent) and has a longer DOA
  • All local anesthetics consist of a lipophilic end and a hydrophilic end separated by a hydrocarbon chain.  The lipophilic end is essnetial for anesthetic activity.  Esters have a -CO and Amides have a -NH froup linking hydrocarbon to the lipophilic aromatic ring.

3

What are the side effects of Bupivacaine?

  • differential blockade (desired in many cases)
  • highly CV toxic
  • TNS
  • Cauda equina syndrome
  • Allergy- rare.  If there is an allergy it's more likely to be the preservative (methylparaben) than the drug itself.
  • Vasodilator
  • Direct IV injection of Bupivacaine can lead to sudden cardiovascular collapse

4

When is Bupivacaine contraindicated?

  • Pt. refusal
  • Inability to cooperate
  • Coagulopathies
  • Hypovolemia
  • Infection at site of injection
  • Inexperience of clinician
  • Caution with meds like Cimetidine and Propranolol which inhibit CYP450 system and could help produce Bupivacaine toxicities.

5

What is the dose of Bupivacaine?

  •  Max Dose: 2.5mg/kg
  • Epidural:
    • 0.25%- 0.5%

    • 15-50mL

    • DOA 3-5 hrs

  • Spinal
    • 0.5% (Isobaric)-0.75%(Hyperbaric)
    • 15-20mg total
    • Lasts 1.5hrs- 3hrs
  • PNB- minor
    • 0.25%-0.5%
    • 15-20mL
    • DOA 3-6hrs, 4-7hrs w/ epi
  • PNB- major
    • 0.25%-0.5%
    • 30-50 mL
    • DOA 6hrs- 12hrs
    • Onset: 20-30 mins

6

What are the pharmacokinetics of Bupivacaine (how is it metabolized)?

  • Bupivacaine is an amide local anesthetic.  Amides are transported to the liver and metabolized by the CYP450 system.  Intial metabolism converts LA to an amino caroboxylic acid before eventual N-dealkylation and subsequent hydrolysis of the drug.  This process takes longer than ester metabolism, which takes place in the blood.  Therefore amides have longer elimination 1/2 times and a higher risk for systemic toxicity.
  • There is some uptake into the lungs
  • Metabolism is dependent on hepatic blood flow

 

7

What is the MOA/ pharmacodynamics of Lidocaine?


  • Blocks Na+ channels in nerve cells while in the closed/ inactive state preventing depolarization and impulse transmission 



  • Holds the nerve under threshold, thereby decreasing the chance of action potential
     

8

What is the drug class/ chemical structure of Lidocaine?

  • Lidocaine is an aminoamide local anesthetic.
  • All local anesthetics consist of a lipophilic end and a hydrophilic end separated by a hydrocarbon chain.  The lipophilic end is essnetial for anesthetic activity.  Esters have a -CO and Amides have a -NH froup linking hydrocarbon to the lipophilic aromatic ring.

9

What are the side effects of lidocaine?

  • TNS
  • High incidence of Cauda Equina syndrome (do not use 5% lidocaine in continuous spinal infusion)
  • CV toxicity
  • vasodilation

10

What are the contraindications to lidocaine?

  • Pt. refusal
  • Inability to coooperate
  • Coagulopathies
  • Infection at side of injection
  • Hypovolemia
  • Inexperience of clinician

11

What is the dose of Lidocaine?

  • Max Dose= 4mg/kg; 7mg/kg w/ epi
  • Epidural
    • 1-2%
    • 15-30mL
    • Onset: 5-15 min
    • DOA: 1.5-2hrs
  • Spinal
    • 1.5-5% (hyperbaric)
    • 1-2mL
    • DOA: 30min - 90min
  • PNB- minor
    • 1%
    • 5-20mL
    • DOA: 1-2 hrs, w/ epi: 2-3hrs
  • PNB- major
    • 1-2%
    • 30-50mL
    • Onset: 10-20min
    • DOA: 2-4 hrs

12

How is Lidocaine metabolized, what are the pharmacokinetics?

  • Lidocaine is an amide local anesthetic.  Amides are transported to the liver and metabolized by the CYP450 system.  Intial metabolism converts LA to an amino caroboxylic acid before eventual N-dealkylation and subsequent hydrolysis of the drug.  This process takes longer than ester metabolism, which takes place in the blood.  Therefore amides have longer elimination 1/2 times and a higher risk for systemic toxicity
  • There is some uptake into the lungs which acts as a reservoir and should help prevent toxicity
  • Metabolism is dependent on hepatic blood flow

13

What are signs and symptoms of local anesthetic toxicity?

  • circumoral numbness
  • ringing in the ears
  • metallic taste
  • vision changes
  • dizziness
  • slurred speech
  • reslessness
  • twtiching in teh face then extremities (indicative of impending seizures)
  • hypotension
  • arrhythmias
  • decreased SVR and CO
  • wide QRS and PRI
  • myocardial depression
  • CV arrest

14

What is the pKa of Lidocaine?

7.9- fast onset

15

At physiological pH, what % of Lidocaine is ionized? unionized?

  • Ionized- 76%
  • unionized- 24%

16

What is the % protein binding of Lidocaine?

65%- moderate DOA

17

What is the E 1/2 t of Lidocaine?

Typically 96 mins.

18

What are the 2 active metabolites of Lidocaine?

  • Xylidide
  • Monoethylglycinexylide

19

What is the mechanism of action/ Pharmacokinetics of Procaine?


  • Blocks Na+ channels in nerve cells while in the closed/ inactive state preventing depolarization and impulse transmission

    Holds the nerve under threshold, thereby decreasing the chance of action potential
     

20

What is the drug class/ chemical structure of Cocaine?

  • Cocaine is an aminoester local anesthetic
  • It is an ester of benzoic acid

21

What are the side effects of Cocaine?

  • Euphoria
  • Coronary vasospasm
  • Myocardial ischemia
  • Ventricular arrhythmias
  • HTN
  • tachycardia
  • increased myocardial O2 demand
  • SNS stimulation (blocks the reuptake of NE & Dopa
  • It is the only local anesthetic that is a potent VASOCONSTRICTOR
  • Causes a dose dependent decrease in uterine bloodflow and fetal hypoxemia

22

What are the contraindications to using Cocaine?

  • Cocaine is contraindicated in most every case aside for sinus surgery or ENT cases where vasoconstriction is desired
  • It is only used in patients with CV stability.

23

What is the dose of Cocaine?

  • Max dose: 3mg/kg
  • it is only used topically

24

What are the pharmacokinetics of Cocaine/ how is it metabolized?

  • Cocaine is an ester local aneshetic; however, it has a unique metabolism.
  • It is the only ester that is metabolized in the liver by liver esterases and the CYP450 system.
  • It's water soluble metabolites are excreted in the urine

25

What is the DOA of Cocaine?

30-40 min after intranasal application, 5min after IV or smoked.

26

What is the MOA/ pharmacodynamics of Procaine?


  • Blocks Na+ channels in nerve cells while in the closed/ inactive state preventing depolarization and impulse transmission

    Holds the nerve under threshold, thereby decreasing the chance of action potential
     

27

What is the drug class/ chemical structure of procaine?

  • It is an aminoester local anesthetic
  • It is the ester protype

28

What are the side effects of Procaine?

  • Procaine is not used topically
  • Procaine is not used for Bier blocks
  • Procaine is not used in epidurals
  • If allergy suspected, it is unlike due to the drug, but rather to PABA (para aminobenzoic acid), an intermediary in ester hydrolysis
  • If allergy to esters is supected, it is OK to give amides.
  • LA toxicity
  • vasodilation
  • High incidence of nausea
  • Pseudocholinesterase deficiency or anticholinesterase drugs can increase the risk of system toxicity of esters.
  • Metabolite of procaine interferes with the efficacy of sulfanoamide antibiotics
  • Not currently a favorite due to slow onset and short DOA

29

What are the contraindications of Procaine?

  • Not for Bier blocks
  • Not for epidurals
  • Not for topical use
  • Pt. refusal
  • inability to coooperate
  • coagulopathies
  • hypovolemia
  • infection at site of injection
  • inexperience of clinician

30

What is the dose of procaine?

  • Max dose- 7mg/kg
  • Epidural
    • procaine not used in epidurals
  • Spinal
    •  
  • PNB-minor
  • PNB-major

31

How is Procaine metabolized, what are the pharmacokinetics?

  • Procaine is an ester local anesthetic.  It is metabolized  by plamsa esterases in the blood.
  • PABA is an intermediary in ester metabolism and can cause allergy.
  • Caution in patients with pseudocholinesterase definciency or those on anticholinesterase drugs.

32

What is the pKa of Procaine?

8.9

33

What is the % ionized of Procaine? % unionized?

  • ionized- 98%
  • unionized- 3%

34

What is the E 1/2 t of Procaine?

9 minutes

35