Clinical Evaluation of Antihypertensive Effects of Prazosin Hydrochloride

ABSTRACT

Prazosin hydrochloride, a new antihypertensive agent with a unique sympatholytic mode of action, was evaluated in 35 cases with essential hypertension. The treatment was started with 3 or 4 mg of prazosin daily divided into 2 or 3 doses, and the dosage was gradually increased weekly up to 20 mg per day depending on the response of the blood pressure. Observations with this drug varied from three to ten weeks, the average being five weeks. In 21 out of 35 cases (60.0%), satisfactory reductions in systolic and diastolic blood pressures with prazosin were noted in both supine and standing positions. These were accompanied by no significant postural hypotension. In 15 out of 21 cases of satisfactory responders, the diastolic blood pressure fell to 90mmHg or less, and in five cases out of 14 poor responders prazosin was given only for three weeks. The average time lapse before effectiveness of the drug in mild, moderate and severe hypertensive cases was 3.3, 3.5 and 6.5weeks, respectively. The average daily effective dosage of prazosin in these groups was 7.1, 9.1 and 12.0mg, respectively. The cardinal unpleasant symptoms appeared in eight out of 35 cases during the medication. These included postural dizziness, weakness, headache, drowsiness and urinary frequency. However, in all cases, except one in which urinary frequency was noted, the symptoms were mild and transient disappearing spontaneously despite continued administration of prazosin. No significant changes were noted in complete blood conuts and routine urinalysis as well as in S-GOT, S-GPT, blood urea nitrogen and serum creatinine levels examined during and after medication.