Clonidine hydrochloride

How it works

It stimulates central alpha-2 adrenoceptors, reducing sympathetic outflow from the brain to lower peripheral vascular resistance, heart rate and blood pressure.

Prescribing in practice

• Do not stop abruptly, as sudden withdrawal can cause a dangerous rebound hypertensive crisis, so always taper the dose.
• Sedation, dry mouth and a slow heart rate are common, and it should be used cautiously with other sedating or rate-limiting drugs.
• Use caution in bradyarrhythmias and significant cerebrovascular or cardiovascular disease.

Monitoring

Monitor blood pressure and heart rate, with particular vigilance for rebound hypertension if treatment is interrupted.

Counselling the patient

• Never stop this medicine suddenly; reductions must be gradual and supervised.
• It may cause drowsiness and a dry mouth, so take care with driving until you know how it affects you.
• Report fainting, a very slow pulse or a sudden rise in blood pressure if a dose is missed.

Evidence & guidelines

The rebound hypertension risk on abrupt withdrawal of centrally acting alpha-2 agonists is well established, and clonidine remains a recognised option for resistant hypertension in current prescribing references.