Also called adrenoceptor-blocking agents or alpha blockers, these drugs stop the stimulation of alpha-adrenergic receptors at the nerve endings of the sympathetic nervous system by hormones with adrenaline-like characteristics. The drugs dilate the arteries, causing a fall in blood pressure, so they are used to treat hypertension and also benign enlargement of the prostate gland. Examples of this group of drugs are doxazosin, indoramin, phentolamine and prazosin. The drugs should be used with caution as some may cause a severe drop in blood pressure when first taken.