What is the recommended subcutaneous dose of tetracaine for adult patients?

Subcutaneous Tetracaine Dosing for Adults

The recommended subcutaneous dose of tetracaine for adult patients is 1.5 mg/kg without epinephrine, with a maximum safe dose calculated based on patient weight. 1

Dosage Calculation and Administration

• Calculate maximum dose: Maximum dose (mg) = 1.5 mg/kg × patient weight (kg)

• Available concentrations:

  Concentration (%)	mg/mL
  1.0	10
  0.5	5
  0.25	2.5
  0.125	1.25

• Volume to administer: Volume (mL) = Maximum dose (mg) ÷ Concentration (mg/mL)

Duration of Action and Clinical Considerations

• Duration of action: 180-600 minutes (3-10 hours) 1
• For comparison with other local anesthetics:
  • Lidocaine: 4.4 mg/kg without epinephrine
  • Bupivacaine: 1.3 mg/kg without epinephrine
  • Ropivacaine: 3 mg/kg

Special Populations and Dose Adjustments

• Elderly patients: Consider dose reduction due to potential for decreased clearance
• Patients with hepatic or renal impairment: Dose reduction may be necessary
• For specific procedures, the lowest effective dose should be used

Monitoring and Safety

• Monitor vital signs during administration

• Watch for signs of systemic toxicity:

  • Perioral numbness
  • Tinnitus
  • Seizures
  • Cardiovascular depression

• If toxicity occurs:

  1. Get help and ventilate with 100% oxygen
  2. Provide airway/ventilatory support as needed
  3. Manage seizures with benzodiazepines if necessary
  4. Consider lipid emulsion therapy for severe toxicity

Clinical Applications

Tetracaine provides longer-lasting anesthesia compared to lidocaine, making it suitable for procedures of short to medium duration. When used subcutaneously, it provides effective local anesthesia for various procedures while avoiding the pain associated with infiltration of other local anesthetics 2.

Potential Pitfalls

• Avoid exceeding the maximum recommended dose to prevent systemic toxicity
• Use caution when applying near mucous membranes, as absorption is increased
• Be aware that higher doses have been used in specific settings (e.g., flexible bronchoscopy) 3, but these should not be routinely employed without appropriate monitoring and expertise

Always calculate the dose based on the patient's actual weight and use the lowest effective concentration and volume to achieve the desired anesthetic effect.