How long does avapro (irbesartan) take to fully work?

Depends on reason...: For taking avapro (irbesartan). Avapro (irbesartan) is a class of medications known as arbs, which can be used for heart failure, high blood pressure, and disease of the heart muscle, to name a few. The medicine itself reaches active levels in the bloodstream within hours of taking it, but the clinical effect you are looking for depends on the reason it was prescribed.

About a month: Should take about a month to see full effect.