RECENT ADVANCES IN PHARMACOLOGICAL MANAGEMENT OF HYPERTENSION IN DIABETIC-PATIENTS WITH NEPHROPATHY - EFFECTS OF ANTIHYPERTENSIVE DRUGS ON KIDNEY-FUNCTION AND INSULIN SENSITIVITY

Hypertension is often seen in Type 1 and Type 2 diabetic patients, particularly in those with nephropathy, and the progression of diabetic nephropathy is closely related to blood pressure elevation. Thus, the effects of antihypertensive drugs on kidney function and insulin sensitivity in diabetic patients are of great clinical importance. Successful antihypertensive treatment has been shown to slow the progression of diabetic nephropathy. Several results from short term studies have suggested that angiotensin converting enzyme (ACE) inhibitors may be advantageous over other conventional antihypertensive agents in reducing albuminuria in both hypertensive and normotensive diabetics with microalbuminuria or persistent proteinuria. However, the decline in glomerular filtration rate during ACE inhibitor treatment is comparable to that during effective treatment with conventional antihypertensive drugs in hypertensive Type 1 diabetic patients with overt nephropathy. Whether ACE inhibitors possess a specific effect in preventing the development of diabetic nephropathy remains to be seen in properly designed long term studies. Although calcium antagonists may preserve kidney function or possess a renoprotective effect in hypertensive Type 2 diabetics with nephropathy, firm evidence supporting this contention seems to be lacking and also requires long term evaluation. Increasing attention is being directed toward the effect of antihypertensive drugs on insulin sensitivity in diabetic patients: ACE inhibitors and alpha-1-adrenoceptor blocking agents have been shown to improve this sensitivity. Despite the widespread involvement of calcium in hormone secretion and action, calcium antagonists appear to have little effects on the glucoregulatory and calcium-regulatory hormones within the drug dosages used in clinical practice. Several clinical variables, such as the presence or absence of hypertension, overt nephropathy and microalbuminuria, or a combination of variables should be accounted for when evaluating critically the cumulative data on the effects of antihypertensive drugs on kidney function and albuminuria in the variety of diabetic patient groups. Understanding the pharmacokinetic and pharmacodynamic characteristics of antihypertensive drugs will be of clinical importance in diabetic patients with advanced nephropathy (glomerular filtration rate of < 30 ml/min) and/or other complications, such as impaired gastric motility or gastroparesis, and will thereby lead to a more rational management of hypertension in those patients.