Some men can respond to Doxazosin alone. I did not.
Here is an interesting study comparing high blood pressure medications and their effect on erectile function.
The link between high blood pressure and ED is complex because ED is a side-effect of certain medications prescribed for hypertension.This was best illustrated by the Treatment of Mild Hypertension Study (TOMHS) that included 557 hypertensive men aged 45-69 years. They received a placebo or one of five drugs: acebutolol, amlodipine, chlorthalidone, doxazosin or enalapril. Sexual function was assessed at baseline and annually during follow-up (48 months). At baseline, 14.4% of the men reported problems with sexual function. ED was positively related to age, systolic blood pressure and previous use of an anti-hypertensive agent.
This a-blocker is probably the anti-hypertensive with the best-documented beneficial effect on erectile function. In TOMHS, the incidence of ED was lowest in patients using doxazosin and highest in those on chlorthalidone (a thiazide-like diuretic). The disappearance of ED was greater in the doxazosin group (87.5%) than for all the other drugs combined (55%). However, this effect did not achieve statistical significance.
Reference:
Grimm RH Jr, Grandis GA, Prineas RJ et al. for the TOMHS Research Group. Long-term effects on sexual function of five antihypertensive drugs and nutritional hygienic treatment in hypertensive men and women. Treatment of Mild Hypertension Study (TOHMS). Hypertension 1997;29:8-14