Cardiovascular parameters and catecholamines in volunteers during passive orthostasis. Influence of antihypotensive drugs.

To evaluate the therapeutic value of various antihypotensive agents we investigated amezinium (AMZ; CAS 30578-37-1), dihydroergotamine (DHE; CAS 511-12-6), midodrine (MDD; CAS 42794-76-3), and oxilofrine (OXF; CAS 365-26-4) in volunteers during passive orthostasis in a randomized double-blind study against placebo (PCB). Blood pressure, heart rate, and circulating catecholamines were determined before and after i.v. injections of the mentioned agents before and during 10 min of passive orthostasis. Echocardiographic and venous plethysmographic data were obtained during resting before and after the administration of the drugs. Resting heart rate decreased after injection of PCB, AMZ, DHE, and MDD. During tilting no significant changes in heart rate could be observed. Blood pressure remained unchanged at rest and during orthostasis after all agents injected. DHE and MDD lowered circulating noradrenaline. Echocardiographic parameters were changed after administration of AMZ (increase in stroke volume index (SVI) and ejection fraction (EF)), MDD (increase in enddiastolic volume index and SVI), and OXF (increase in SVI, EF, and cardiac index). The venous capacity of the lower left leg was only significantly decreased after injection of DHE, indicating an increased venous tone of the leg veins. The observed changes in sympathetic and cardiovascular parameters are in agreement with their sympathomimetic actions and allow a differential therapeutic classification: DHE and MDD are suitable agents for patients with sympathotonic orthostatic reaction; if asympathotonic orthostatic reaction occurs MDD, AMX and OXF should be recommended to those patients.