Maximum Dose of Mephentermine for Treating Hypotension
The maximum single dose of mephentermine for treating hypotension is 6 mg intravenously as a bolus dose, which can be titrated according to blood pressure response.
Dosage Guidelines for Mephentermine
Mephentermine is a sympathomimetic amine that acts as a vasopressor for treating hypotension. Based on available evidence, the dosing recommendations are:
- Initial IV bolus dose: 6 mg 1
- Infusion dosing:
- Starting dose: 0.1-2.0 mg/kg per minute 2
- Can be titrated to desired effect based on blood pressure response
Efficacy and Potency
Mephentermine has been shown to be significantly more potent than ephedrine for treating hypotension:
- The minimum effective dose (ED50) of mephentermine is approximately 3.7 mg (95% CI 2.4 to 5.7 mg) 3
- The potency ratio of ephedrine to mephentermine is approximately 1:6.8 (95% CI 6.0 to 7.5) 3
- This means mephentermine is nearly 7 times more potent than ephedrine for treating hypotension
Clinical Applications
Mephentermine is particularly useful in:
- Hypotensive (usually distributive) shock with low systemic vascular resistance (SVR) that is unresponsive to fluid resuscitation 2
- Examples include hypotensive septic shock and neurogenic shock
- Post-spinal hypotension, particularly in obstetric patients undergoing cesarean section 4, 1
Administration Considerations
When administering mephentermine, consider the following:
- Route: Intravenous (IV) or intraosseous (IO) administration is recommended 2
- Monitoring: Continuous blood pressure monitoring is essential during administration
- Titration: Start at the lowest effective dose and titrate based on blood pressure response
- Side effects: May cause tachycardia, bradycardia, arrhythmias, and hypertension 2
Precautions and Contraindications
- Extravasation risk: Extravascular administration can result in severe skin injury 2
- Management of extravasation: Phentolamine (0.1-0.2 mg/kg up to 10 mg diluted in 10 mL of 0.9% sodium chloride) injected intradermally at the extravasation site may help counteract dermal vasoconstriction 2
- Contraindications: Similar to other sympathomimetic amines, use with caution in patients with cardiovascular disease, hyperthyroidism, and in combination with MAO inhibitors
Comparison with Other Vasopressors
Studies comparing mephentermine with other vasopressors have shown:
- Mephentermine is as effective as ephedrine for managing hypotension during spinal anesthesia 4
- Both mephentermine and phenylephrine can maintain hemodynamics within 20% of baseline values 1
- Mephentermine tends to cause tachycardia compared to phenylephrine, which may cause bradycardia 1
In summary, while mephentermine is a potent vasopressor for treating hypotension with a maximum single bolus dose of 6 mg IV, careful titration based on blood pressure response is essential to optimize outcomes and minimize adverse effects.