Phenylephrine

How it works

It stimulates alpha-1 adrenoceptors on vascular smooth muscle to produce peripheral vasoconstriction, raising systemic vascular resistance and blood pressure.

Prescribing in practice

• The rise in blood pressure can trigger a reflex bradycardia, so heart rate must be watched and the drug used with caution where bradycardia or fixed cardiac output is a concern.
• It is preferred where vasoconstriction without inotropy is desired, but extravasation of concentrated solutions can cause local ischaemia and tissue necrosis.
• Use with caution in patients with hypertension, severe coronary disease or peripheral vascular disease, and account for exaggerated responses with monoamine oxidase inhibitors.

Monitoring

Continuous blood pressure and heart rate monitoring is required, ideally with the infusion titrated to a defined haemodynamic target.

Counselling the patient

• This is given by trained staff with close blood pressure monitoring.
• Report any pain or skin changes at the infusion site promptly.

Evidence & guidelines

Its use as a vasopressor, including for maternal hypotension during spinal anaesthesia for caesarean section, is well established in anaesthetic practice.