Haemodynamic effect of prazosin during hyperosmolar mannitol load in essential hypertension

The haemodynamic effect of one-week prazosin therapy was investigated in 21 patients with essential hypertension (9 of WHO stage I, 12 of stage II). There was a significant decrease of mean arterial blood pressure (MABP) and total peripheral resistance (TPR) at rest after prazosin therapy in both stage I and II hypertensives. Under the condition of hyperosmolar load (after mannitol infusion), prazosin has no significant influence on the haemodynamics in stage I hypertensives. Contrastingly, in stage II essential hypertension, prazosin increased cardiac index, stroke volume index and decreased MABP and TPR in comparison with the values before therapy and after placebo. Microcirculation in the forearm and thigh muscles was not influenced. The results indicate that prazosin improves subclinical impairment of cardiac function, which is present in stage II and is so an advantageous antihypertensive drug preferable for stages II and higher of the disease.