What is the recommended dose for tetracaine (amethocaine) subcutaneous administration?

Tetracaine Subcutaneous Dosing Guidelines

The maximum recommended dose of tetracaine for subcutaneous administration is 1.5 mg/kg without epinephrine, as established by the American Academy of Pediatrics guidelines. 1, 2

Dosing Parameters

• Maximum dose without epinephrine: 1.5 mg/kg 1
• Duration of action: 180-600 minutes 1
• Available concentrations: typically 0.25-1% solutions 2

Concentration Conversion Chart

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

Administration Guidelines

1. Calculate the maximum safe dose based on patient weight:

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

2. Calculate volume to administer based on tetracaine concentration:

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

3. Administer the lowest effective dose to minimize risk of toxicity 2

Special Considerations

High-Risk Populations

• Reduce dose by 30% in infants younger than 6 months 1
• Use caution in patients with hepatic or renal impairment 2
• Elderly patients may require dose reduction due to decreased metabolism 2

Safety Monitoring

• Monitor vital signs during administration
• Watch for signs of systemic toxicity:
  • Perioral numbness
  • Tinnitus
  • Seizures
  • Cardiovascular depression 1

Treatment of Local Anesthetic Toxicity

If toxicity occurs, follow these steps:

1. Get help and ventilate with 100% oxygen
2. Provide airway/ventilatory support and chest compressions if needed
3. Manage seizures with benzodiazepines (e.g., IV midazolam 0.1-0.2 mg/kg)
4. Administer 20% lipid emulsion (1.5 mL/kg over ~1 minute) 1

Clinical Context

While some research suggests higher doses of tetracaine may be used in specific clinical settings (such as the study showing doses up to 158 mg for bronchoscopy 3), these applications are outside standard practice and should not be routinely followed without specialist consultation. The established guidelines from the American Academy of Pediatrics clearly define the maximum safe dose as 1.5 mg/kg without epinephrine 1.

For comparison, other commonly used local anesthetics have different maximum doses:

• Lidocaine: 4.4 mg/kg without epinephrine; 7.0 mg/kg with epinephrine 1
• Bupivacaine: 1.3 mg/kg without epinephrine; 3.0 mg/kg with epinephrine 1

Tetracaine's extended duration of action (3-10 hours) makes it particularly useful for procedures requiring prolonged analgesia, but this also increases the importance of adhering to safe dosing limits.