With long-term therapy, autoregulation by the body s own compensatory mechanisms results in vasodilatation, reduction of peripheral vascular resistance and return of the cardiac output to normal. In some patient groups, such as blacks and the elderly, the thiazides are particularly efficacious. However, they tend to be less effective in younger, white patients. Hydrochlorothiazide bendrofluazide, Adverse effects The main concerns about thiazide diuretics are their metabolic side effects, although, at low doses, these are less likely to be a problem. They may cause hypokalaemia due to renal potassium wasting.
Acute gout is another common side effect of thiazides, even in low doses.
Impotence may occasionally be a problem. Rarer side effects include nausea, headache, rashes, photosensitivity and blood dyscrasias. Beta-blockers act by blocking the action of noradrenaline at b adrenoceptors throughout the circulatory system and elsewhere. Their major effect is to slow the heart rate and reduce its force of contraction. Beta-blockers also cause some reduction in renin release and central sympathetic tone.