Clonidine suppression test - plasma

Last updated: Wednesday, 14, April, 2004

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Item Process

5 mL blood in lithium heparin tube.


Plasma adrenaline, noradrenaline - HPLC.

  1. The patient must be relaxed and comfortable in bed.
  2. A slow intravenous infusion of saline is commenced.
  3. After 30 minutes (to allow patient to settle after venepuncture) a baseline specimen for plasma catecholamines is collected.
  4. The patient is given 300 µg clonidine hydrochloride orally.
  5. Blood for catecholamines is collected at 60, 120, 150 and 180 minutes.
  6. The drip is removed and the patient checked for fitness to leave the centre; drowsiness is a possible side effect.
Reference Interval

Plasma adrenaline and noradrenaline levels should both drop to 50% of their baseline level.


Diagnosis of phaeochromocytoma, when other investigations are equivocal. May be replaced by plasma metanephrines.


Failure to suppress plasma adrenaline and/or noradrenaline indicates autonomous release of one or both catecholamines from a tumour.


Elliot WJ and Murphy MB. Am J Med 1988; 84: 419-424.

Lenders JW et al. Ann N Y Acad Sci 2002; 970: 29-40.