Clonidine

How it works

It stimulates central alpha-2 adrenoceptors in the brainstem, reducing sympathetic outflow and noradrenaline release, which lowers heart rate and blood pressure and produces sedation and analgesia.

Prescribing in practice

• Abrupt withdrawal after sustained use can precipitate rebound hypertension and tachycardia, so taper rather than stop suddenly and avoid in patients with significant bradyarrhythmia.
• Causes dose-dependent hypotension, bradycardia and sedation that can be additive with anaesthetic agents and other CNS depressants.
• Use cautiously in cerebrovascular or ischaemic heart disease and in those with impaired renal function, who may need a reduced dose.

Monitoring

Monitor heart rate, blood pressure and conscious level closely during and after perioperative administration.

Counselling the patient

• Expect drowsiness, a dry mouth and possible light-headedness when standing.
• Do not stop the medicine abruptly if you have been taking it regularly.

Evidence & guidelines

Perioperative use is supported by anaesthetic guidance and trials showing reduced opioid requirement and attenuated haemodynamic stress responses.