Oral sympathomimetics are effective in the treatment of nasal congestion through stimulation of alpha-adrenergic receptors in the blood vessels of the nasal mucosa. This vasoconstrictor activity has resulted in the general recommendation that such pressor amines not be used in patients with hypertension. No prospective studies have examined the safety of sustained-release pseudoephedrine in hypertensive patients.Volunteers (N = 28) with controlled hypertension participated in a randomized, double-blind, placebo-controlled, crossover study that examined the cardiovascular effects of 120 mg of sustained-release pseudoephedrine taken on a twice daily basis. Physician-investigators measured blood pressure and heart rate using mercurial sphygmomanometers during acute and steady-state phases. Compliance was verified with pill counts and serum drug levels. Symptom questionnaires were completed by the volunteers.While a strong statistical correlation was found over time, with minimal increases in mean arterial pressure and heart rate, pseudoephedrine administration did not result in statistically significant changes in any cardiovascular parameter. Mild disturbances in sleeping pattern and urinary retention in some male subjects were the only significant symptoms detected.We conclude that while sustained-release pseudoephedrine appears safe for the majority of medically controlled hypertensive patients without statistically significant effects on blood pressure or heart rate our studies did show an upward trend in these parameters which, in a larger population of hypertensive patients, may prove to be clinically significant.