Beta Adrenergic Drugs

B1

Increases HR, myocardial contractility, nodal conduction, & renin release

B1

Uses Gs → increases cAMP-PKA

Dobutamine

Predominant B1 Agonist w/ some B2 & A1 activity at higher doses → for short term cardiac support, stress test → requires continuous ECG monitoring for tachyarrhythmias

Dopamine

Dose-dependent effects: B1 (increased inotropy & chronotropy) @ moderate, dopaminergic @ low, & A1 (vasoconstriction & increased BP) @ high → for select shock states w. hypotension/decreased cardiac output

Epinephrine

B1 agonist w/ B2 & A1 agonism; dose-dependent effects: B2 (vasodilation & bronchodilation) @ low, B1 & B2 (increased HR & contractility, bronchodilation, vasodilation) @ moderate, A1 w/ some B1 (positive inotropy & chronotropy, increased BP/vascular resistance)

Norepinephrine

B1 agonist w/ stronger A1 activity (A1 predominates clinically) → vasoconstriction, minimal bronchodilation, increased inotropy/chronotropy ± reflex bradycardia → for septic shock

Isoproterenol

Strong, nonselective B1/B2 agonist → bronchdilation & peripheral vasodilation, increased inotropy/chronotropy → for shock, symptomatic bradycardia (2nd to atropine failure)

B2

Uses Gs → increased cAMP-PKA

B2

In smooth muscle: phosphorylates MLCK (inhibits → decreases smooth muscle contractility) and KCa channels (activates → hyperpolarization → decreases smooth muscle contractility) → vasodilation & bronchoconstriction

B2

In skeletal muscle: promote K+ uptake from bloodstream → vasodilation, glycogenolysis, glucagon release

Albuterol

Selective B2 Agonist: relaxes bronchial smooth muscle & shifts K+ into cells

Salmeterol

Long-acting selective B2 Agonist: supports maintenance bronchodilation

Terbutaline

Selective B2 Agonist: promotes bronchodilation & IC K+ shifts; only available PO/SQ

B1 Blockade

Decreased HR, SA/AV conduction, contractility, myocardial O2 demand, renin release

B2 Blockade

Bronchoconstriction, blunted B2 vasodilation, & impaired glycogenolysis & glucose recovery during hypoglycemia

B3

relaxes bladder detrusor, promotes adipose lipolysis & brown fat thermogenesis