Dental Local Anesthetic Agents & Vasoconstrictors

Agents at a glance (approximate durations as commonly taught, Malamed)

Agent	Class and metabolism	Pulpal duration	Points to remember
Lidocaine 2% with epinephrine 1:100,000	Amide; liver	About 60 min	Reference drug; widely used in pregnancy
Mepivacaine 3% plain	Amide; liver	About 20 min infiltration, 40 min block	Mild vasodilator, so it works without a vasoconstrictor; good for short procedures and when epinephrine is unwanted
Mepivacaine 2% with levonordefrin 1:20,000	Amide; liver	About 60 min	Levonordefrin: avoid with tricyclic antidepressants
Articaine 4% with epinephrine 1:100,000 or 1:200,000	Amide with a thiophene ring and an ester side chain; mostly plasma esterases	About 60–75 min	Short half-life (about 20–45 min); good infiltration diffusion; label not for children under 4
Prilocaine 4% plain or with epinephrine 1:200,000	Amide; liver and lungs	Plain: short by infiltration, about 40–60 min by block	Metabolite o-toluidine → methemoglobinemia
Bupivacaine 0.5% with epinephrine 1:200,000	Amide; liver	About 90–180 min; soft tissue up to about 12 h	Long surgery and postoperative pain; not for children or patients at risk of self-injury

Esters (procaine, benzocaine, tetracaine) are hydrolyzed by plasma pseudocholinesterase; their metabolite PABA causes most true allergies to local anesthetics.
Quick class check: amides have an 'i' in the name before '-caine' (lidocaine, mepivacaine, articaine, prilocaine, bupivacaine).

Why add one: slows absorption (lower blood levels and toxicity), prolongs and deepens anesthesia, and reduces bleeding.
Epinephrine acts on α and β receptors; at dental doses β₂ effects can lower diastolic pressure slightly while β₁ raises heart rate and contractility.
Levonordefrin acts mostly on α receptors with about one-sixth the vasopressor potency of epinephrine, so it is supplied at 1:20,000.
Ratio to concentration: 1:1,000 = 1 mg/mL, so 1:100,000 = 0.01 mg/mL (10 µg/mL) and 1:200,000 = 0.005 mg/mL.
Cartridges with vasoconstrictor contain sodium (meta)bisulfite as an antioxidant: consider a plain solution for patients with a documented sulfite allergy, many of whom are steroid-dependent asthmatics.
All local anesthetics in dentistry are vasodilators; cocaine is the vasoconstricting exception.

Agent	Notes
Benzocaine (ester), up to 20%	Poorly absorbed; localized allergy possible; methemoglobinemia warning (FDA) in young children
Lidocaine (amide) 2–5%	Absorbed more systemically; counts toward the total dose
Lidocaine/prilocaine periodontal gel	Non-injection anesthesia for scaling in pockets

Calling articaine an ester: it is an amide with an ester side chain.
Using levonordefrin with a patient on a tricyclic antidepressant.
Thinking plain mepivacaine 3% lasts as long as lidocaine with epinephrine.
Forgetting the bisulfite in epinephrine-containing cartridges when a patient reports sulfite allergy.

Amide vs ester: amides have two 'i's in the name (lIdocaIne, mepIvacaIne); esters have one (procaIne, benzocaIne). Articaine is the classic exception: amide with an ester side chain.

Pick an answer to see right away whether it is correct and why.

Which local anesthetic is metabolized mostly in the plasma rather than the liver?
Which agent is associated with methemoglobinemia through its metabolite o-toluidine?
How many mg of epinephrine per mL are in a 1:200,000 solution?
A patient on amitriptyline needs anesthesia. Which vasoconstrictor should be avoided?
Why does plain mepivacaine 3% work reasonably well without a vasoconstrictor?

0 of 5 answered

Answer key: 1 C · 2 B · 3 B · 4 D · 5 C

Dental School Map · Original study material, written and checked by our team; always confirm clinical decisions against current guidelines.