Local Anesthetic Maximum Dosing
Compare max safe doses for lidocaine, articaine, bupivacaine, mepivacaine, prilocaine. Weight-based with vasoconstrictor options.
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Lidocaine: 4.5/7 mg/kg Bupivacaine: 2/2.5 mg/kg (longest) Articaine: 4/7 mg/kg (dental)
Ready to run the numbers?
Why: Exceeding max doses risks LAST. Each agent has different mg/kg limits and duration.
How: Weight × mg/kg limit, capped by absolute max. Vasoconstrictor increases safe dose.
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🦷 Dental - Articaine
Adult dental procedure using 4% articaine with epinephrine
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⏱️ Long Procedure - Bupivacaine
Extended nerve block using long-acting bupivacaine
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👶 Pediatric - Lidocaine
10-year-old child requiring local anesthesia
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💊 Mepivacaine Plain
Short procedure without vasoconstrictor
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💉 Prilocaine for Cardiac Patient
Prilocaine preferred in cardiac-compromised patient
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Patient Information
Agent Selection
Risk Factors
For informational purposes only — not medical advice. Consult a healthcare professional before acting on results.
🏥 Health Facts
LAST: lipid emulsion 1.5 mL/kg bolus. Have Intralipid available.
— ASRA
What are Local Anesthetics?
Local anesthetics are medications that reversibly block nerve conduction, providing numbness in a specific area without affecting consciousness. They are classified into two main chemical groups: amides (lidocaine, bupivacaine, articaine, mepivacaine, prilocaine) and esters (procaine, benzocaine). Understanding their pharmacology helps select the optimal agent for each clinical scenario.
Lidocaine
Most versatile agent. Rapid onset, intermediate duration.
- Max: 4.5 (plain) / 7 (epi) mg/kg
- Onset: 2-5 min
- Duration: 30-60 / 90-180 min
Articaine
Best tissue penetration. Preferred for dental procedures.
- Max: 4 (plain) / 7 (epi) mg/kg
- Onset: 1-3 min
- 95% protein binding
Bupivacaine
Longest duration. Ideal for postoperative pain control.
- Max: 2 (plain) / 2.5 (epi) mg/kg
- Duration: 4-8 / 6-12 hours
- Higher cardiotoxicity risk
Local Anesthetic Agents Comparison
| Agent | Max (plain) | Max (with epi) | Onset | Duration (with epi) | pKa |
|---|---|---|---|---|---|
| Lidocaine | 4.5 mg/kg | 7 mg/kg | 2-5 min | 90-180 min | 7.9 |
| Articaine | 4 mg/kg | 7 mg/kg | 1-3 min | 60-230 min | 7.8 |
| Bupivacaine | 2 mg/kg | 2.5 mg/kg | 5-10 min | 240-720 min | 8.1 |
| Mepivacaine | 4.4 mg/kg | 6.6 mg/kg | 3-5 min | 120-180 min | 7.6 |
| Prilocaine | 6 mg/kg | 8 mg/kg | 2-4 min | 60-180 min | 7.9 |
How to Select an Agent
Short Procedure
Lidocaine or Mepivacaine - quick onset, adequate duration
Dental/Oral
Articaine - superior bone penetration
Long Duration
Bupivacaine - hours of analgesia
Cardiac Patient
Prilocaine - less cardiovascular effect
Avoid Vasoconstrictor
Use plain mepivacaine - intrinsic vasoactivity
Pediatric
Lidocaine most studied; reduce all doses 30%
Special Considerations
Prilocaine Warning
High doses (>400 mg) can cause methemoglobinemia due to o-toluidine metabolite. Avoid in patients with methemoglobin reductase deficiency.
Bupivacaine Cardiotoxicity
Bupivacaine has higher cardiotoxicity than other agents. Avoid rapid injection and intravascular administration. Have lipid emulsion ready.
LAST Treatment Protocol
Local Anesthetic Systemic Toxicity (LAST) is a medical emergency requiring immediate recognition and treatment.
Signs and Symptoms of LAST
CNS (usually first):
- • Perioral numbness, metallic taste
- • Tinnitus, visual changes
- • Agitation, confusion
- • Seizures
- • Coma
Cardiovascular:
- • Hypertension → Hypotension
- • Tachycardia → Bradycardia
- • Ventricular arrhythmias
- • Asystole
Treatment Protocol
- 1Stop injection and call for help
- 2Airway management: 100% O2, consider intubation
- 3Seizures: Midazolam/lorazepam (avoid propofol initially)
- 4Cardiac arrest: Standard ACLS, consider epinephrine dose reduction
- 5Lipid Emulsion 20%: Bolus 1.5 mL/kg over 1 min, then 0.25 mL/kg/min infusion
Clinical Pearls
Aspiration First
Always aspirate before injection. Negative aspiration doesn't guarantee extravascular placement but reduces risk.
Incremental Dosing
Inject in small increments (3-5 mL), pausing between injections to assess for early toxicity signs.
Ultrasound Guidance
US-guided blocks allow lower doses and reduce intravascular injection risk. Consider for all peripheral blocks.
Have Lipid Ready
Intralipid 20% should be immediately available wherever local anesthetics are used. Know the location.
Weight-Based Limits
Never exceed max mg/kg dose regardless of clinical need. Consider alternative techniques if more needed.
Duration Planning
Match agent duration to procedure length. Bupivacaine for long procedures, lidocaine for shorter ones.
Frequently Asked Questions
Can I mix different local anesthetics?
Yes, mixing is common (e.g., lidocaine + bupivacaine for quick onset and long duration). Toxicity is additive - calculate total dose of all agents.
When should I use epinephrine?
Epinephrine reduces systemic absorption, prolongs duration, and reduces bleeding. Avoid in digital blocks, end-arterial territories, and patients with uncontrolled hypertension.
Is there a true allergy to local anesthetics?
True allergy is rare (<1%). Most reactions are vasovagal, epinephrine-related, or preservative reactions. Amides (lidocaine) don't cross-react with esters (procaine). Consider allergy testing if history unclear.
Concentration Quick Reference
Understanding percent concentrations helps convert between % and mg/mL for accurate calculations.
| Concentration | mg/mL | Common Use |
|---|---|---|
| 0.25% | 2.5 mg/mL | Bupivacaine infiltration |
| 0.5% | 5 mg/mL | Bupivacaine blocks |
| 1% | 10 mg/mL | Lidocaine infiltration |
| 2% | 20 mg/mL | Lidocaine dental/blocks |
| 4% | 40 mg/mL | Articaine, topical |
Formula: % × 10 = mg/mL (e.g., 1% = 10 mg/mL, 2% = 20 mg/mL)
Duration of Action Comparison
Short
Procaine
30-60 min
Medium
Lidocaine, Mepivacaine
60-120 min
Long
Bupivacaine, Ropivacaine
4-8+ hours
With Epi
All agents
+50-100%
Pediatric Considerations
Children have different pharmacokinetics and are more susceptible to toxicity. Dose calculations must be weight-based.
Key Differences in Children
- • Lower protein binding = more free drug
- • Immature hepatic metabolism
- • Higher cardiac output increases absorption
- • Use conservative dosing (70-80% of adult)
- • Lidocaine is most studied in pediatrics
Pediatric Max Doses
- • Lidocaine: 3-4.5 mg/kg (5-7 with epi)
- • Bupivacaine: 2-2.5 mg/kg (3 with epi)
- • Use lower concentrations when possible
- • Always calculate total dose before injection
Pre-Procedure Checklist
- Confirm patient weight and calculate max dose
- Verify allergy status
- Know location of lipid emulsion
- Ensure monitoring equipment available
- Resuscitation equipment accessible
- IV access (for regional blocks)
Max Dose Quick Reference
| Agent | Plain | With Epi | For 70 kg Adult |
|---|---|---|---|
| Lidocaine | 4.5 mg/kg | 7 mg/kg | 315-490 mg |
| Bupivacaine | 2.5 mg/kg | 3.5 mg/kg | 175-245 mg |
| Mepivacaine | 4.5 mg/kg | 7 mg/kg | 315-490 mg |
| Articaine | 7 mg/kg | 7 mg/kg | 490 mg |
Key Safety Reminders
- • Always aspirate before injection to check for intravascular placement
- • Inject incrementally (3-5 mL at a time) with pauses
- • Know where lipid emulsion is located before starting any block
- • Monitor for early CNS symptoms: perioral numbness, metallic taste, tinnitus
- • Stop immediately if signs of toxicity appear
LAST Emergency Response
Intralipid 20% Dosing:
- • Bolus: 1.5 mL/kg over 1 minute
- • Infusion: 0.25 mL/kg/min
- • Repeat bolus: If no response in 5 min
- • Max dose: 12 mL/kg total
- • Continue CPR: During lipid administration if in cardiac arrest
- • ECMO: Consider for refractory cardiac arrest
- • Avoid propofol: Not a substitute for lipid emulsion
- • Vasopressin: Preferred pressor if needed
ASRA LAST Checklist
Post the ASRA LAST checklist in all procedure areas. Download from asra.com/last
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