What is the recommended subcutaneous (sq) dosing for tetracaine?

Subcutaneous Tetracaine Dosing Recommendations

There is no standardized subcutaneous dosing recommendation for tetracaine in current guidelines, but based on local anesthetic safety parameters, the maximum recommended dose is 1.5 mg/kg without epinephrine. 1

General Dosing Considerations

Tetracaine is an ester-type local anesthetic with the following characteristics:

• Duration of action: 180-600 minutes (significantly longer than many other local anesthetics) 1, 2
• Maximum safe dosage: 1.5 mg/kg without epinephrine 1, 2

Dosing Algorithm for Subcutaneous Administration

When administering tetracaine subcutaneously, consider the following approach:

1. Calculate maximum safe dose: 1.5 mg/kg (without epinephrine) 1
2. Select appropriate concentration: Typically available as 0.25-1% solutions
3. Calculate volume: Based on concentration and required dose
   • For example: For a 70 kg adult at maximum dose (1.5 mg/kg)
     • Maximum total dose = 105 mg
     • Using 1% solution = 10.5 mL maximum volume

Important Safety Considerations

• Anatomical location matters: Absorption rates vary significantly by injection site 3

  • Higher absorption areas (face, scalp) require dose reduction
  • Lower absorption areas (extremities) may tolerate standard dosing

• Patient factors affecting dosing:

  • Age: Reduce dose in elderly and very young patients
  • Weight: Calculate based on actual body weight
  • Hepatic/renal function: May require dose reduction in impaired patients

• Monitoring requirements:

  • Vital signs monitoring is essential during administration
  • Observe for signs of systemic toxicity (perioral numbness, tinnitus, seizures)

Pitfalls and Caveats

• Avoid inadvertent intravascular injection: Always aspirate before injection 3
• Risk of systemic toxicity: Tetracaine has a narrow therapeutic window compared to amide anesthetics like lidocaine 4
• Allergic reactions: More common with ester anesthetics like tetracaine than with amide anesthetics
• Avoid use on mucous membranes: Rapid absorption increases toxicity risk 4
• Consider alternative agents: For procedures requiring less duration, shorter-acting agents may be safer

Alternative Local Anesthetics for Subcutaneous Use

If tetracaine is not appropriate, consider these alternatives with established subcutaneous dosing:

• Lidocaine: 7 mg/kg maximum dose with epinephrine; 4-5 mg/kg without 1
• Bupivacaine: 3 mg/kg maximum dose with epinephrine 1
• Ropivacaine: 3 mg/kg maximum dose 1

Remember that the choice of local anesthetic should be based on the required duration of action, the procedure being performed, and individual patient factors that might affect metabolism and clearance of the drug.