Phenylephrine

[PHW2:p196-197]

 

Direct-acting sympathomimetic

 

Pharmacodynamics

Mechanism of action

Alpha1 agonist

No effect on beta receptors

Effects

CVS

Increased SVR
--> Increased BP

Possible reflex bradycardia
--> Possible decrease in CO

Not proarrhythmic

 

CNS

No stimulatory effects

 

Renal

Decreased renal perfusion
* Similar to NE

 

Uterus

Decreased uteroplacental blood flow
--> Avoid in pregnancy

Pharmacokinetics

 

Metabolism

[PHW2:p197]

Metabolised in liver by MAO

Metabolite and route of elimination UNKNOWN

 

Action profile

IV
* Duration of action = 5 - 10 min

IM or S/C
* Onset = 15 min
* Duration of action = up to 1 hour

Pharmaceutics

[PHW2:p196]

10mg in 1 mL

 

Clinical

[PHW2:p196]

Administration

Boluses 50-100 microgram IV

2-5 mg IM or S/C
--> Slower onset but more prolonged action

 

 

Usage

To increase a low SVR associated with spinal anaesthetics or other drugs

Nasal decongestant

Mydriatic agent