Why is blood pressure so hard to control in patients with type 2 diabetes?

Resistance to antihypertensive drugs is common in hypertensive patients with type 2 diabetes. This is unfortunate because hypertension is one of the most important risk factors for development of cardiovascular events, and the goal blood pressure level is set lower in diabetic subjects than in nondiabetic subjects. Previous outcome trials in diabetic subjects have mainly focused on end points such as microalbuminuria or the incidence of cardiovascular events rather than on reduction of blood pressure; some reports, however, have suggested mechanisms for the drug resistance. These include several clinical conditions known to be associated with difficulty in reducing blood pressure specifically in diabetes mellitus: change in the renin-angiotensin system and chymase, volume overload, central sympathetic hyperactivity, sleep apnea, secondary hypertension, pseudoresistance (white coat hypertension), and poor compliance related to subclinical depression. In this review, the authors focus on the mechanisms of resistance to antihypertensive therapy (particularly for monotherapy with either angiotensin-converting enzyme inhibitors or angiotensin II antagonists) in the treatment of diabetic hypertension.