Hygiene Atlas

Atlas · Plate VIII · Pharmacology and Local Anesthesia · 08

Local anesthetic agents

Every injectable dental anesthetic in the US is an amide, metabolized in the liver, although articaine is mostly broken down in plasma; esters such as benzocaine are used mainly as topicals. Lidocaine 2% with epinephrine is the reference agent. Mepivacaine 3% works without a vasoconstrictor, prilocaine can cause methemoglobinemia, articaine diffuses well and bupivacaine gives long-lasting anesthesia for long procedures.

High-yield facts · 14

  1. All injectable dental anesthetics in the US are amides; esters are used mainly as topicals (benzocaine, tetracaine).S14
  2. Amides are metabolized in the liver; esters by plasma pseudocholinesterase. Articaine is mostly broken down in plasma because of its ester side chain.S14
  3. Lidocaine 2% with 1:100,000 epinephrine is the reference agent; lidocaine has topical anesthetic properties too.S14
  4. Lidocaine 2% with epi: pulpal anesthesia about 60 min, soft tissue about 3-5 h.S14T1
  5. Mepivacaine 3% plain: pulpal about 20 min by infiltration and 40 min by block; useful when a vasoconstrictor is contraindicated.S14T1
  6. Mepivacaine is only mildly vasodilating, which is why it works without a vasoconstrictor.S14
  7. Prilocaine 4% plain: pulpal about 10-15 min infiltration, 40-60 min block; metabolite o-toluidine can cause methemoglobinemia.S14T1
  8. Articaine 4% with epinephrine (1:100,000 or 1:200,000): thiophene ring improves diffusion; half-life about 27 minutes.S14
  9. Articaine and prilocaine 4% have been linked to more paresthesia after mandibular blocks; many clinicians avoid 4% agents for IA blocks.S14
  10. Bupivacaine 0.5% with 1:200,000 epinephrine: long acting (pulpal 1.5-3 h, soft tissue up to about 12 h); good for long surgery and postop pain.S14T1
  11. Half-lives (approximate): lidocaine 1.6 h, mepivacaine 1.9 h, prilocaine 1.6 h, articaine 0.5 h, bupivacaine 2.7 h.T1
  12. pKa (approximate): lidocaine 7.7-7.9, mepivacaine 7.6, prilocaine 7.9, articaine 7.8, bupivacaine 8.1; the lower the pKa, the faster the onset.T1
  13. Benzocaine topical (up to 20%) is poorly absorbed and acts locally; it can cause methemoglobinemia.S14
  14. EMLA/Oraqix (lidocaine 2.5% + prilocaine 2.5%) is a noninjectable periodontal pocket gel.S14

Facts are written in our own words; each tag links to its source. Values marked "sources vary" differ between references, so check the one your program uses.