Mephentermine sulfate
Mephentermine sulfate (Wyamine)
Mephentermine sulfate
(meh- FEN-ter-meen)
Pregnancy Category: C Wyamine Sulfate (Rx)

Classification: Adrenergic agent, indirectly acting; vasopressor

See Also: See also Sympathomimetic Drugs .

Action/Kinetics: Acts indirectly by releasing norepinephrine from its storage sites and directly by exerting a slight effect on alpha and beta-1 receptors and a moderate effect on beta-2 receptors mediating vasodilation. Causes increased CO; also elicits slight CNS effects. IV: Onset, immediate; duration: 15-30 min. IM: Onset, 5-15 min; duration: 1-2 hr. Metabolized in liver. Excreted in urine within 24 hr (rate increased in acidic urine).

Uses: Hypotension due to anesthesia, ganglionic blockade, or hemorrhage (only as emergency treatment until blood or blood substitutes can be given).

Contraindications: To treat hypotension caused by chlorpromazine. In combination with MAO inhibitors.

Special Concerns: Use with caution in CV disease, in chronically ill clients, and in treating shock secondary to hemorrhage. Safety and efficacy have not been demonstrated in children.

Side Effects: Anxiety, cardiac arrhythmias, increased BP (especially in those with heart disease).

Additional Drug Interactions: Mephentermine will potentiate hypotensive effects of phenothiazines.

How Supplied: Injection: 15 mg/mL, 30 mg/mL

Dosage
?IV, IM Hypotension during spinal anesthesia.
IV, Adults: 30-45 mg; 30-mg doses may be repeated as required; or, IV infusion, Adults and children: 0.1% (1 mg/mL) mephentermine in D5W with the rate of infusion and duration dependent on client response. IV, Pediatric: 0.4 mg/kg (12 mg/m ²) as a single dose.
Prophylaxis of hypotension in spinal anesthesia.
IM, Adults: 30-45 mg 10-20 min before anesthesia. IM, Pediatric: 0.4 mg/kg (12 mg/m ²) as a single dose.
Shock following hemorrhage.
Not recommended, but IV infusion of 0.1% in D5W may maintain BP until blood volume is replaced.