Hemodynamic, reflexive, and metabolic alterations induced by acute and chronic timolol therapy in hypertensive man.

The hemodynamic, cardiovascular, and metabolic effects of acute (intravenous) and prolonged (four weeks oral) timolol treatment were assessed in 16 patients with mild or moderate essential hypertension. Fifteen patients completed the outpatient study and ten showed a fall in mean arterial pressure of at least 10 mm Hg. They also demonstrated a significant fall in supine systolic (7%), diastolic (9%), and mean arterial pressure. Hemodynamic evaluation was performed in 13 patients and cardiac index was found to be reduced with both intravenous (20%) and oral timolol (13%). There was no correlation between the decrease in cardiac index and arterial pressure. Calculated total peripheral resistance rose with intravenous timolol and returned toward, but not below, pretreatment values with the oral therapy. Left ventricular ejection rate also fell significantly with intravenous timolol but returned toward pretreatment levels with oral therapy. Plasma renin activity was reduced similarly with both modes of administration and its reduction also did not correlate with the fall in arterial pressure. Plasma volume fell in eight of 13 patients. Reflexive responses to the Valsalva maneuver were considerably modified by both intravenous and oral timolol but responses to 50 degrees upright tilt and handgrip were not. Timolol is an effective oral antihypertensive agent with similar hemodynamic and metabolic effects to propranolol.