Effect of systemic autonomic inhibition on the hemodynamic response to antihypertensive therapy with timolol

To evaluate the role of systemic autonomic tone in the hemodynamic response to beta-inhibitors, the hemodynamic effects of long-term timolol therapy were studied in hypertensive patients under two sets of conditions: at rest and after pharmacologic systemic autonomic inhibition (SAI). Hemodynamic studies were performed in every subject at the end of a 4-week placebo period and again at the end of a 9-week treatment period. The antihypertensive effect of timolol was associated with decreased cardiac output and unchanged peripheral resistance at rest and with unchanged cardiac output and decreased peripheral resistance after SAI. The hemodynamic response to SAI during the two studies was also markedly different. The findings provide evidence of increased alpha-adrenergic component of systemic autonomic tone during long-term therapy with timolol.