Effect of clonidine on serum inorganic phosphorus in patients with essential arterial hypertension.

The decrease in arterial blood pressure in patients with essential arterial hypertension treated with clonidine is associated, in 88.9% of cases, with a rise in serum inorganic phosphorus. The increase of inorganic phosphorus in the serum of patients with hypophosphataemia, during clonidine therapy, is higher (P less than 0.001) than in hypertensive patients with normal values of serum phosphorus (P less than 0.01). This effect is more significant in overweight hypertensive patients (P less than 0.0005) than in normal weight hypertensives (P less than 0.02). No correlation was noted between the rise of serum inorganic phosphorus and the decrease in systolic and diastolic arterial blood pressure. The rise of serum phosphorus concentration in hypertensive patients is attributed to inhibition of insulin release and enhancement of growth-hormone secretion induced by clonidine.