Isoproterenol

[PHW2:p197-198]

Aka: isoprenaline

 

 

Pharmacodynamics

Mechanism of action

[PHW2:p197]

Highly potent synthetic catecholamine with actions at beta1 and beta2

No actions on alpha receptors

Effects

[PHW2:p197]

CVS

Stimulation of beta1 receptors
--> Increased HR, CO, myocardial contractility, automaticity

Stimulation of beta2 receptors
--> Decreased SVR

Overall BP change is variable (may increase or decrease)

Oxygen delivery to myocardium may be decreased significantly
* Tachycardia --> Reduced diastolic filling time of coronary vessels
* Decreased SVR --> Reduced diastolic BP
* Some coronary vasodilation --> May attenuate the decrease in oxygen delivery

 

Respiratory

Bronchodilation

Inhibition of histamine release in lungs

Increased anatomical dead space

Increased V/Q mismatch

 

CNS

Stimulatory effect on CNS

 

Splanchnic

Increased mesenteric and renal blood flow

 

Metabolic

Increased blood glucose and free fatty acid

Pharmacokinetics

Absorption

[PHW2:p198]

Oral administration
* Well absorbed
* High first-pass hepatic metabolism

 

 

Metabolism

[PHW2:p198]

Rapidly metabolised by COMT within liver

 

Elimination

[PHW2:p198]

Significant fraction is excreted unchanged in urine

 

 

Pharmaceutics

1mg/mL for IV infusion

30mg oral tablets

Clinical

Usage

Use to treat severe bradycardia associated with AV block or beta-blocker

Used to be used for treatment of reversible airway obstruction
--> No longer used due to increased mortality
* Specific beta2 agonists (e.g. salbutamol) are now used instead