Nursing Pharmacology:  Autonomic Pharmacology Adrenergic Drugs 

Isoproterenol (Isuprel)

• Isoproterenol activates ß adrenergic receptors (both ß₁ - and ß₂ -receptor subtypes)

  • Isoproterenol exhibits limited action at α adrenergic receptors

• i.v. influsion of isoproterenol results in a slight decrease in mean blood pressure with a marked drop in diastolic pressure.

• ß₂-adrenergic receptor-mediated reduction in peripheral resistance (reflected in the diastolic pressure effects) is primarily due to vasodilation of skeletal muscle vasculature.

  • Renal and mesenteric vascular beds are also dilated.

• Activation of cardiac ß₁-adrenergic receptors by isoproterenol cause an increase in both contractility and heart rate.

• Activation of ß₂-adrenergic receptors by isoproterenol result in both bronchial and gastrointestinal (GI) smooth muscle relaxation.

• Isoproterenol and ß₂-selective adrenergic agonists inhibit antigen-mediated histamine release.

• Isoproterenol:  Limited therapeutic uses include:

  • Emergency settings to treat heart block or severe bradycardia

  • Management of torsades de pointes (a ventricular arrhythmia)

• Isoproterenol (Isuprel) adverse effects include:

  • Palpitations

  • Tachycardia

  • Arrhythmias

  • Coronary insufficiency

Dobutamine (Dobutrex)

• Structurally similar to dopamine (Intropin).

  • Pharmacological effects exerted through interaction with a and ß adrenergic receptor interactions

    • No effect on release

    • No action through dopamine receptors

• Pharmacological effects are due to complex interactions of (-) and (+) enantiometic forms present in the clinically used racemate with a and ß adrenergic receptors.

• Dobutamine (Dobutrex) is a positive inotropic agent usually causing limited increase in heart rate.

  • Positive inotropism is mediated through ß adrenergic receptor activation. Some peripheral a₁ activity causes modest vasoconstriction, an effect opposed by dobutamines ß₂ effects.

•   Dobutamine (Dobutrex): Adverse Effects

  • Significant blood pressure and heart rate increases may occur.

  • Ventricular ectopy

  • Increased ventricular following rate in patient with atrial fibrillation.

  • Increased myocardial oxygen demand that may worsen post-infarct myocardial damage

• Dobutamine (Dobutrex): Therapeutic Use

  • Short-term management of pump failure following surgery, during acute congestive heart failure, or post-myocardial infarction.

  • Uncertain long-term efficacy.

Hoffman, B.B and Lefkowitz, R.J, Catecholamines, Sympathomimetic Drugs, and Adrenergic Receptor Antagonists, In, Goodman and Gillman's The Pharmacologial Basis of Therapeutics,(Hardman, J.G, Limbird, L.E, Molinoff, P.B., Ruddon, R.W, and Gilman, A.G.,eds) TheMcGraw-Hill Companies, Inc.,1996, pp.199-242.