Core pharmacology

Class Group

ADRENERGIC

Legacy Cicm Level

Level 3

Introduction

synthetic catechol derivative of isoprenaline

Indications Uses

1. Inotropic support in low cardiac output secondary to MI, cardiac surgery, cardiomyopathy
2. Cardiac stress testing

Presentation

Is a racemic mixture. White
powder for reconstitution(250mg) or Clear fluid 12.5mg/ml in 20ml vials.
Should not be
mixed with alkaline solutions (HCO3)

Main Action

the + enantiomer is a potent α1 antagonist
and β1 agonist, the -ve enantiomer has
opposite effects on α1 causing agonism and
is less potent (10%) β1 agonist.

Mechanism of action

Predominant mechanism is via direct acting B1 stimulation (increased cAMP) and retains a small amount of B2 effects

Physiological effects

composite of α and β actions.
Mostly β1 effect: ↑ ino+ chrono tropy and MVO2.
Mild β2 eff¬ects.

Detail:

CVS
- Beta1 effects lead to increased SA node activation (increased chronotropy), increased dromotropy and increased inotropy, thereby increasing cardiac output (inotropy greatest)
- Coronary artery vasodilator
- Beta-2 activity tends to decrease LVEDP and SVR, contributing to increased CO and cardiac index
- Increased MVO2
- Increased risk of arrhythmias (especially at doses >10mcg/kg/min)
- Should be avoided in patients with cardiac outflow obstruction (AS, tamponade)

Resp
- Modest pulmonary vasodilation
- Inhibits HPV

Renal- Increased RBF due to increased CO may occur

Adverse Effects Toxicity

1. Arrhythmias (especially at doses >10mcg/kg/min)
2. Arrest in fixed output patients (AS, tamponade)
3. Increased MVO2
4. Eosinophilic myocarditis in prolonged infusion

Absorption

IV, dose starts at 5mcg/kg/min uptitrate to
e¬ffect, max 40mcg/kg/min

Distribution

Small vd

Volume of distribution

0.2L/kg

Metabolism

via COMT then gluruonidation hepatically

Excretion

urine as inactive metabolites

Half-life

2 minutes

Route And Dose

IV Infusion
Dose range 0.5-40mcg/kg/min. Response within 2 minutes