Proceedings: The relation of antihypertensive treatment to plasma lipids and other vascular risk factors in hypertensives

Comparative effects of propranolol and prazosin upon serum lipids in thiazide- treated hypertensive patients

Earlier reported thiazide-induced changes in serum lipid concentrations were confirmed with increased triglyceride and total cholesterol levels. However, lipoprotein cholesterol ratios were unchanged. Propranolol caused further increases in triglyceride and very low-density lipoprotein cholesterol, and lowered high-density lipoprotein cholesterol and the high-density lipoprotein:total cholesterol ratio. With the addition of prazosin to the polythiazide regimen, there was a significant increase in serum high-density lipoprotein cholesterol when compared with the placebo.

Thiazide-induced disturbances in carbohydrate, lipid, and potassium metabolism

Long-term thiazide diuretic therapy for hypertension is associated with disturbances in carbohydrate, lipid, and potassium metabolism that theoretically may have serious adverse effects. It appears that diuretic-induced hypokalemia interferes with production of insulin, producing mild elevations of blood glucose in nondiabetic patients. The insulinopenia worsens glucose metabolism in prediabetic and type II diabetic patients. Increases in low-density lipoprotein cholesterol, triglycerides, and the low-density lipoprotein/high-density lipoprotein cholesterol ratio are frequently seen following thiazide treatment of hypertension. These changes are more pronounced in younger patients. Decrements of serum potassium of 0.6 mEq/L are commonly observed with diuretic therapy. Usually, patients remain asymptomatic and no potassium replacement is necessary. In patients with underlying heart disease, however, alterations in potassium metabolism may produce increased frequency and complexity of ventricular ectopic activity. All these metabolic disturbances appear to be, in part, dose related, and there is currently no evidence that they have clinical significance.

Lipid abnormalities in untreated maturity-onset diabetics and the effect of treatment

Plasma cholesterol and serum triglyceride levels and frequency of lipoprotein abnormalities were investigated in 126 untreated maturity-onset diabetics and 126 age- and sex-matched control subjects. Serum triglyceride levels were higher (mean: 1.67 mmol/l) and type IV hyperlipoproteinaemia occurred more frequently (16.7%) in the diabetic group as compared with the controls (1.29 mmol/l and 4.8% respectively). These findings were not explained by an excessive frequency of renal disease, hypertension or drug treatment amongst the diabetics. Normal men showed higher serum triglyceride (mean: 1.36 mmol/l) and lower plasma cholesterol (mean: 5.6 mmol/l) levels than normal women (1.21 mmol/l and 6.4 mmol/l respectively). No sex difference was seen amongst the diabetics. Triglyceride levels fell after one month of dietary treatment but only remained lowered in diabetics who required sulphonylureas for glycaemic control. After treatment for one year the correlation between serum triglycerides and blood glucose rose from r = 0.15 (NS) before treatment to r = 0.43 (p less than 0.001). Similarly the correlation between serum triglycerides and ponderal index rose from r = 0.19 (NS) to r = 0.28 (p less than 0.02).

Diuretics: mechanism of action and clinical application

Despite the bewildering number of diuretics available to the physician, these drugs can be divided into 4 main groups, characterised by their site of action on sodium reabsorption in the kidney. Drugs acting on the ascending limb of the loop of Henle have a powerful but short acting diuretic effect; they include frusemide, ethacrynic acid and bumetanide. The benzothiadiazines and related compounds have a moderate diuretic action spread over a longer period, whilst the potassium-sparing diuretics, triamterene, amiloride and spironolactone, have only a weak diuretic effect but a marked ability to diminish urinary potassium excretion. The fourth group is made up of miscellaneous substances which function as vasodilator or osmotic agents. The pathogenesis of oedema formation in heart failure is outlined and a logical approach to treatment suggested. Duiretics are being increasingly used in the treatment of non-oedematous states, in particular hypertension, diabetes insipidus and hypercalciuria; their exact role in pregnancy and acute renal failure remains controversial. Side-effects can be related to their effect on electrolyte excretion and include hypokalaemia, hyponatraemia, hyperkalaemia and hyperuricaemia. The incidence of disturbed carbohydrate tolerance in previously normal individuals is low. Other less common side-effects are also discussed.