ACE inhibitors with thiazides is a combination medicine containing both an angiotensin-converting-enzyme inhibitor (ACE inhibitor) and a thiazide.
An ACE inhibitor blocks the angiotensin converting enzyme from converting angiotensin I to angiotensin II. This results in a decrease in angiotensin II causing vasodilation and therefore a reduction in blood pressure.
Thiazide diuretics decrease active re-absorption of sodium and chloride ions by inhibiting the sodium/chloride co-transporter in the distal convoluted tubule. This causes an increase in urine production (diuresis) and results in a decrease in blood volume and a reduction in blood pressure.