Table 1.

Comparative analysis of vasopressors used in obstetric anesthesia

No.	Drug	Mechanism of Action	Advantage	Disadvantage
1	Methoxamine	α1 receptor agonist	No inotropic or chronotropic effect. Tachyphylaxis has seldom been observed	Reflex bradycardia. Adverse effect on fetal acid-base status
2	Mephentermine	α and β receptor agonist. Both direct and indirectly acting	Economical and does not need multiple dilutions as compared to Phenylephrine	Tachyphylaxis. Little evidence available on placental transfer and its fetal metabolic impact
3	Metaraminol	α and β receptor agonist. Both direct and indirectly acting	No adverse effect on fetal acid-base status as compared to ephedrine	Tachyphylaxis
4	Phenylephrine	Selective α1 receptor agonist at clinical doses	Immediate onset and short duration of action. Ideal for continuous infusion. No adverse effect on fetal acid-base status as compared to ephedrine	Tachyphylaxis. Reflex bradycardia and concerns regarding decreased maternal cardiac output
5	Ephedrine	α and β receptor agonist. Both direct and indirectly acting	Economical and does not need multiple dilutions as compared to Phenylephrine. No bradycardia	Tachyphylaxis. Adverse effect on fetal acid-base status as compared to Phenylephrine