A method for evaluating postural hypotension in conscious rabbits as a model to predict effects of drugs in man

Because of the importance of postural hypotension as a side effect of antihypertensive drugs in man, an experimental model has been developed that permits the investigation of blood pressure response to tilting. Conscious rabbits were placed on a tilting table and tilted rapidly from horizontal to vertical position. Blood pressure was recorded continuously throughout the whole period. The individual orthostatic reaction was expressed as an orthostatic index. The experimental data obtained with guancydine, clonidine, guanethidine, prazosin, and dihydralazine were compared with clinical observations with regard to the impairment of orthostatic reaction; dihydralazine did not agree, but there was a good agreement for guancydine, clonidine, guanethidine, and prazosin. Although complete agreement between the experimental data and clinical observations does not exist, the model seems to be sufficient to differentiate between drugs with low or high potential for postural hypotension.