Local Anesthetics

Question 1

What are the actions of local anesthetics?

Answer 1

• block nerve conduction of sensory impulses from periphery to the CNS
• Abolish sensation (motor activity at hight concentrations) in a limited area of the body without producing unconsciousness

Question 2

• Procedure that keep the drug at the ______ prolong the periods of anesthesia
• Preparations of local anesthetics often contain a vasoconstrictor, usually __________
• As a consequence ________ of the drug is enhanced and _______ are reduced

Answer 2

• Procedure that keep the drug at the nerve prolong the periods of anesthesia
• Preparations of local anesthetics often contain a vasoconstrictor, usually epinephrine
• As a consequence neuronal uptake of the drug is enhanced and systemic toxic effects are reduced

Question 3

What is the metabolism of ester-linked local anesthetics and amide-linked local anesthetics?

Answer 3

• Ester-linked metabolized by tissue and plasma esterases
  (pseudocholinesterases)
• Amide-linked local anesthetics in general are degreaded by liver microsomal cytochrome P450

Question 4

Local anesthetics MOA?

Answer 4

MOA: block voltage-gated sodium channels by binding to receptors near intracellular end of channel to block channel

Question 5

• Liposolulbility correlates with both ____ and _______
• Greater ________ also increased toxicity
• The ____ correlates with the speed of onset of action (blocer to body pH)

Answer 5

• Liposolulbility correlates with both potency and duration of action
• Greater liposolubility also increased toxicity
• The pKa correlates with the speed of onset of action (blocer to body pH)

Question 6

What are the short, intermediate and long acting local anesthetics?

Answer 6

Short

• Procaine and Chloroprocaine

Intermediate

• Lidocaine, Mepivacaine, Prilocaine

Long

• Tetracaine, Bupivacaine, Etidocaine, and Ropivacaine

Question 7

What toxicity can be seen with local anesthetics CNS, PNS, CVS, Blood, Allergic reaction?

Answer 7

• CNS: restlessness/tremor > clonic convulsions, respiratory failure, convulsions; can use premedication benzodiazepine for seizure
• PNS: toxic to nerve at high concentrations
• CVS: depress cardiace pacemaker activity/excitability/conduction, arteriolar dilation/hypotension, Cocaine is exception > vasoconstriction/HTN/cardiac arrhythmias; Bupivacaine most cardiotoxic
• Blood: large doses of prilocaine > accumulation of o-toluidine which is oxidizing agent that can make methemeglobin
• Allerigc: ester type > p-aminobenzoic acid derivatives > allergic reaction

Question 8

What drug interactions can be seen with local anesthetics?

Answer 8

• procaine is hydrolyzed in vivo to produce paraaminobenzoic acid (PABA) which inhibits actions of sulfonamides