[Test with clonidine for diagnosing pheochromocytoma].

Noradrenaline, adrenaline and mean arterial pressure prior to and 3 hours after clonidine administration were evaluated in order to assess a value of single dose of 0.3 mg clonidine in the diagnosis of pheochromocytoma. The study involved 12 patients with pheochromocytoma, 17 patients with arterial hypertension, and 9 patients with borderline hypertension. Seven healthy volunteers served as a control group. It was found that clonidine decreased noradrenaline levels in all healthy subjects and patients with the primary blood hypertension and did not affect noradrenaline levels in patients with pheochromocytoma. Clonidine decreased noradrenaline levels in two patients with normal resting noradrenaline levels. Simultaneously, clonidine decreased noradrenaline levels in two patients with normal resting levels of this catecholamine. The obtained results indicate low specificity of the clonidine test and its value in the diagnosis of pheochromocytoma in patients with normal noradrenaline blood levels.