Mean arterial blood pressure (MABP) and mean cerebral blood flow velocity (MCBFV) were analyzed using spectral analysis and cross-correlation functions (CCF) in hypertensive patients. Two antihypertensive drugs, Cozaar and Renitec, were used to investigate their effects on cerebral autoregulation (CA). Seventeen hypertensive patients were chosen and separated randomly into two groups. Another group was recruited with nine age-matched healthy subjects. MABP and MCBFV were acquired in both supine and head-up tilt positions before and after treatment. The ratio of low- to high-frequency power tended to decrease in the Cozaar group, in contrast to the Renitec group. This might indicate that Cozaar has a more manifest effect in suppressing sympathetic nervous system activity. The CCF analysis showed that the mean max CCF value indices in the Renitec group before treatment were significantly different in the supine position from those after two months of treatment (p < 0.05). This might indicate that the time lag (generally existing for normal subjects) was improved after treatment. The mean max CCF time, indices and values
were significantly different from those in healthy subjects during head-up tilt position before treatment (p < 0.05). The CCF analysis revealed that the CA conditions of patients with these two antihypertensive drugs after two months of treatment would close to those of healthy subjects.