What are the recommendations for using prilocaine and lidocaine for local anesthesia?

Recommendations for Using Prilocaine and Lidocaine for Local Anesthesia

For adult patients, the maximum safe dose is 4.5 mg/kg for lidocaine without epinephrine and 7.0 mg/kg for lidocaine with epinephrine, while children should receive no more than 1.5-2.0 mg/kg and 3.0-4.5 mg/kg respectively. 1, 2

Dosing Guidelines

Adult Patients

• Maximum lidocaine dose without epinephrine: 4.5 mg/kg
• Maximum lidocaine dose with epinephrine: 7.0 mg/kg
• For multistage procedures (e.g., Mohs surgery): maximum 500 mg (50 mL of 1% solution) 1
• Use ideal body weight for dose calculation:
  • Men: height in cm - 100
  • Women: height in cm - 105 1

Pediatric Patients

• Maximum lidocaine dose without epinephrine: 1.5-2.0 mg/kg
• Maximum lidocaine dose with epinephrine: 3.0-4.5 mg/kg 1, 2
• Age-specific dosing for prilocaine/lidocaine cream:
  • 0-3 months or <5kg: maximum 1g over 10cm² for 1 hour
  • 3-12 months and >5kg: maximum 2g over 20cm² for 4 hours
  • 1-6 years and >10kg: maximum 10g over 100cm² for 4 hours
  • 7-12 years and >20kg: maximum 20g over 200cm² for 4 hours 3

Administration Methods

Infiltrative Anesthesia

• Recommended for various procedures including biopsies, excisions, wound closure, tissue rearrangement, skin grafting, and laser resurfacing 1
• Use the lowest effective dose and aspirate before injection to avoid intravascular administration 1, 2
• For improved efficacy, consider combining with other forms of local anesthesia for complex procedures 1

Topical Anesthesia (Prilocaine/Lidocaine Cream)

• Apply thick layer (1-2 g/10 cm²) under occlusive dressing 3
• Application times:
  • Minor dermal procedures (venipuncture): at least 1 hour
  • Major dermal procedures (split-thickness skin grafts): at least 2 hours
  • Genital mucous membranes: 5-10 minutes (occlusion not necessary) 3, 4

Toxicity Prevention and Management

Signs of Toxicity

• Early symptoms: circumoral numbness, facial tingling, slurred speech, metallic taste, auditory changes
• Progressive symptoms: hypertension, tachycardia, hallucinations
• Severe cases: seizures, CNS depression, cardiac failure or arrest 1, 2

Prevention Strategies

1. Use lowest effective dose
2. Aspirate needle before each injection
3. Use incremental injections
4. Continuously monitor and communicate with patient 1, 2

Safety Precautions for IV Lidocaine

• Do not use IV lidocaine within 4 hours of nerve blocks or fascial plane blocks
• Do not perform nerve blocks until 4 hours after completion of IV lidocaine infusion
• Remove topical lidocaine patches before starting IV lidocaine infusion 1

Special Considerations

Allergies

• True lidocaine allergy is rare (approximately 1% of adverse reactions) 1, 2
• Alternative options for patients with lidocaine allergy:
  • Ester-type local anesthetics (minimal cross-reactivity with amide types)
  • 1% diphenhydramine injection (longer onset: 5 min vs. 1 min for lidocaine)
  • Bacteriostatic normal saline (0.9% benzyl alcohol in normal saline) 1, 2

Combination Therapy

• Combining methods of local anesthesia is safe and effective for complex procedures:
  • Full-face ablative laser resurfacing: combine infiltrative, topical, and nerve block anesthesia
  • Hair transplantation: combine tumescent and infiltrative anesthesia 1

Specific Applications

Dermatologic Procedures

• Eutectic mixture of lidocaine/prilocaine cream provides effective superficial dermal analgesia when applied under occlusive dressing for 60 minutes 5
• For genital mucosa, lips, and oral mucosa, application time can be reduced 5
• Particularly useful for children undergoing procedures like removal of molluscum contagiosum 4

Venous Access

• Intradermal injection of lidocaine using microneedle devices can provide rapid local anesthesia for peripheral venous cannulation with significant pain reduction 6

Facial Procedures

• Higher doses of diluted lidocaine (up to 21.6 mg/kg) with epinephrine (1:600,000) have been used safely for facelift procedures, yielding peak plasma levels well below toxic thresholds 7

Common Pitfalls and Caveats

• Avoid using IV lidocaine concurrently with other local anesthetic interventions
• Do not use prilocaine/lidocaine cream in neonates with gestational age less than 37 weeks or infants under 12 months receiving methemoglobin-inducing agents 3
• When applying topical anesthetics to children, maintain careful observation to prevent accidental ingestion 3
• Consider the total dose when using multiple forms of local anesthesia simultaneously 1, 3
• For patients with stable cardiovascular disease, small amounts of lidocaine with epinephrine appear safe, but consultation with the patient's cardiologist is recommended in questionable cases 2