1. The effects of clonidine and hydrochlorothiazide on the cardiovascular responses to mental stess were compared in 29 adolescents with essential hypertension.
2. Clonidine therapy was associated with lower diastolic pressures, heart rate and noradrenaline in response to mental stress. By contrast, hydrochlorothiazide resulted in the reduction of systolic pressure only. The mental stress testing produced a greater absolute diastolic pressure response and higher plasma noradrenaline on hydrochlorothiazide therapy.
3. Juveniles with essential hypertension may be more sensitive to central control of blood pressure and more resistant to diuretics.
4. The reduced diastolic pressure and heart rate response to central stimuli during clonidine therapy may be related to decreased adrenergic activity, as indicated by lower plasma noradrenaline.