Efficacy of antihypertensive drugs.

The magnitude of the fall in blood-pressure in response to an antihypertensive drug depends on the level of the pretreatment pressure, and there is a direct relationship between the two in that the higher the pretreatment pressure the greater the fall in pressure in response to treatment. This simple relationship is inherent in the practical situation of titrating the diastolic blood-pressures of a group of hypertensive patients to a predetermined level. It is assumed that notionally the dose of an antihypertensive drug can be increased in all patients until the diastolic pressure is reduced to the predetermined level. When the fall in diastolic pressure (deltaD.P.) is plotted against pretreatment diastolic pressure (P.T.D.P.), the points for all patients lie on a straight line of slope unity and negative deltaD.P.-intercept numerically equal to the predetermined diastolic-pressure level. This straight-line relationship is termed the predetermined ideal response line. Analysis of data from clinical trials shows that, despite the variability inherent in the practical situation, the data appear to conform to this straight-line relationship. The method of assessing the efficacy of antihypertensive agents is essentially a comparison of each experimental point with the theoretical predetermined response line. In its simplest form the method consists in constructing a scatter diagram of deltaD.P. against P.T.D.P. for all patients. Patients can then be classified as responders or non-responders according to their position on the diagram relative to the predetermined response line. This method of assessing the efficacy of antihypertensive agents has several advantages, the most important of which is that it provides a simple method for displaying all the relevant information in a readily comparable form.