Systolic and diastolic blood pressure is lowered in both the supine and standing positions. 6 to 11 mmHg systolic and 5 to 9 mmHg diastolic. The response in the standing position tended to be larger by 3 to 5 mmHg. There was no apparent difference in the blood pressure response of Caucasians and Blacks or of patients above and below age 65. No significant changes were observed in high-density lipoprotein fraction and triglycerides compared to placebo.
Food has little or no effect on the bioavailability.
Plasma elimination is biphasic with a terminal elimination half-life of about 22 hours. There is accumulation of plasma levels of doxazosin following steady state dosing, consistent with the terminal elimination half-life. In a study of elderly hypertensive patients the pharmacokinetic parameters of doxazosin at steady state were similar to those observed in a previous study of young and elderly healthy subjects who received a single oral dose of doxazosin. Doxazosin is extensively metabolized, mainly by 0-demethylation of the quinazoline nucleus or hydroxylation of the benzodioxan moiety. In the treatment of mild to moderate essential hypertension.