A pharmacodynamic and pharmacokinetic assessment of a new alpha‐ adrenoceptor antagonist, doxazosin (UK33274) in normotensive subjects.

1 Doxazosin is a quinazoline derivative, related to prazosin, recently developed for the treatment of hypertension. 2 The intravenous administration of doxazosin (12 micrograms/kg) to six healthy normotensive subjects resulted in significant fall in erect blood pressure, with a corresponding increase in heart rate, but there were no significant changes in supine blood pressure or heart rate. 3 The changes in blood pressure and heart rate were maximal at 6 h after intravenous dosing. With prazosin the maximum effects occurred within the first hours. 4 Pressor response studies with phenylephrine confirmed that doxazosin is a relatively selective postsynaptic alpha-adrenoceptor antagonist. 5 The mean elimination half-life of doxazosin was 11 h. This compared with a T1/2 of 2.5 h for prazosin.