Does Hydrochlorothiazide Interact With Doxazosin?
as with any antihypertensive drug combination (but perhaps more so with doxazosin) there may be additive effects. These effects may lead to orthostatic hypotension or significantly low blood pressure in some patients.
Since patients who need both are usually those with high uncontrolled blood pressure the combination is not very likely to cause any trouble at all.
If these are the only antihypertensive drugs you take then I have to say that this is a strange combination! Doxazosin is not a first-line option for high blood pressure.
I hope it helps!