Plasma Renin Activity During Levodopa Therapy: Significance of Long- and Short-Term Treatment

Plasma renin activity (PRA) was studied in six patients with Parkinson disease under identical conditions of diet and posture before and after seven days of levodopa administration. Significant differences were not found at seven days, nor when the measurement was repeated under similar conditions of sodium excretion after six months of therapy. The PRA responded appropriately to posture before and after therapy. After six months of therapy, sodium restriction resulted in an appropriate response of PRA and aldosterone secretion. A small but significant fall in blood pressure took place seven days after the initiation of levodopa therapy, at which time PRA had not changed significantly. After six months of therapy, blood pressure had returned to control levels. This study suggests that the renin-aldosterone system is not significantly altered by levodopa therapy of Parkinson disease.