Pharmacotherapeutic group: Adrenergic and dopaminergic agents. ATC Code: C01CA06.
Pharmacology: Pharmacodynamics: Phenylephrine is a potent vasoconstrictor that acts almost exclusively by stimulating alpha-1-adrenergic receptors. Such arterial vasoconstriction is also accompanied by venous vasoconstriction. This gives an increase in blood pressure and reflex bradycardia. The potent arterial vasoconstriction gives an increase in the systemic vascular resistance (increase in afterload). The overall result is a reduction in the cardiac output. This is less pronounced in healthy people but it may worsen in cases of previous heart failure. As Phenylephrine effects are linked to its pharmacological properties, they can be controlled by known antidotes.
Pharmacokinetics: The volume of distribution after single dose is 340 litres.
Phenylephrine is metabolised in the liver by monoamine oxidase.
Phenylephrine is mainly excreted via the kidneys as m-hydroxymandelic acid and phenol conjugates.
The duration of effect is 20 minutes after intravenous administration.
The terminal half life of injectable phenylephrine is about 3 hours.
The plasma protein binding is unknown.
There is no data available on the pharmacokinetics in special patient groups.
Toxicology: Preclinical safety data: There is no evidence of genotoxicity or carcinogenicity of phenylephrine. Animal studies are insufficient to evaluate effects on fertility and reproduction.