Epinephrine

• Epinephrine is a potent activator of alpha and ß adrenergic receptors

• Prominent Cardiovascular Effects

Blood Pressure

• Potent vasopressor

  • Systolic pressure increases to a greater extent than diastolic (diastolic pressure may decrease)

    • pulse pressure widens

  • Epinephrine increases blood pressure by:

1. enhancing cardiac contractility (positive inotropic effect): ß₁-receptor effects

2. increasing heart rate (positive chronotropic effect): ß₁-receptor effects.

3. vasoconstriction a₁ receptor effects

   • precapillary resistance vessels of the skin, kidney, and mucosa

   • veins

Vascular Effects

• Epinephrine has significant effects on smaller arteriolar and precapilliary smooth muscle.

Acting through alpha₁ receptors, vasocontrictor effects decrease blood flow through skin and kidney.

• Even at doses of epinephrine that do not affect mean blood pressure, substantially increases renal vascular resistance and reduces blood flow (40%).

• Renin release increases due to epinephrine effects mediated by ß₁-receptors associated with juxtaglomerular cells.

• Acting through ß₂-receptors, epinephrine causes significant vasodilation which increases blood flow through skeletal muscle and splanchnic vascular beds.

Cardiac Effects

• Epinephrine exerts most of its effects effects on the heart through activation of ß₁-adrenergic receptors.

  • ß₂- and a receptors are also present.

  • Heart rate increases

  • Cardiac output increases

  • Oxygen consumption increases

Category: Pharmacology Notes