Local Anesthetics, Amides vs Esters

Ester: Metabolized in the blood plasma and has a high incidence of allergy

  • Allergies to this drug stem from an atypical pseudocholinesterase which is a protein needed to metabolize these drugs
  • They tend to have a cross allergy meaning that if you are allergic to one ester drug you are likely going to be allergic to other esters

Amide: Metabolized in the liver like most other drugs, very low incidence of allergy

Individuals with liver disease or low liver function will have a hard time metabolizing the drug and more drug free in the body increasing its toxicity

Amides

Lidocaine/ Octocaine/ xylocaine

  • Starts to work quickly and spreads to tissues widely
  • Medium duration
  • Anesthetic characteristic will work longer with epinepherine
  • Available topically, IV, Block, Epidural, and as a viscous mouthwash solutions usually use d to treat sores and ulcers

Mepivicaine/ polocaine/ carbocaine

  • Available with levonordefrin which is like epinephrine to last longer and keep the anesthetic concentrated in treatment area
  • Works like lidocaine in terms of less vasodilation than other local anesthetics
  • Not available topically

Prilocaine

  • Available with or without epinepherine, but even without epinephrine it has a longer duration than lidocaine
  • less toxic than lidocaine but also less potent
  • Risk of methemoglobinemia when drug metabolized into an active form of ortho-toluidine

Bupivacaine

  • Less toxic than lidocaine but more potent
  • Very long duration, need to be aware of risk for self harming patients or very young patients due to self inflicting injury when no sensation felt for extended periods

Articaine

  • 5-10% metabolized in the liver and the rest in the blood plasma but still considered amide
  • methylparaben free
  • ability to be lipid soluble meaning it can cross lipid membrane barriers readily like the lipid membrane on our nerves

Esters

Procaine/ Novocaine

  • Very safe but high incidence of allergy
  • Not used in dentistry today
  • Very slow onset and high vasodilation without epinephrine
  • Used to treat IV arrhythmia and uncontrolled seizures

Propoxycaine

Not widely given in dentistry but if patient reports to allergy with this medication they likely are allergic to other esters

Tetracaine

  • 10 times more potent than propoxycaine
  • Slow onset but long duration
  • Not widely used in dentistry

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