Nifedipine does not change how your body absorbs and processes irbesartan, the blood pressure medicine in this combination. The same is true of hydrochlorothiazide, the other part of the combination. The amount of irbesartan in your body stays the same when you take these together.
These medicines are often taken together with some care. Your doctor may change a dose, space them apart or check on you more often. Make sure your doctor and pharmacist know you take both.