Guanfacine in the treatment of hypertension: two years' experience with low dose monotherapy.

The results of one year's treatment of 243 hypertensive patients with guanfacine, given alone in a variety of doses and dosage schedules, were analyzed in terms of antihypertensive efficacy and incidence of side effects. The study comprised 111 women and 132 men with a mean age of 53.7 years and a mean pretreatment blood pressure of 185/105 (+/- 23/11) mmHg. After one year's treatment the mean blood pressure was 146/89 mmHg for patients receiving guanfacine once a day (mean dose 2.2 mg), 153/90 mmHg for patients on a twice-daily dosage schedule (mean daily dose 3.5 mg), and 159/92 mmHg for patient on a thrice-daily schedule (mean daily dose 4.9 mg). There were no differences between the three groups as regards sex, age, body weight, previous treatment, or pretreatment blood pressure. Normalization of blood pressure occurred in 75% of the patients treated with guanfacine given once daily and in 52% of those given guanfacine thrice-daily. The incidence of sedation and dryness of the mouth was lowest on the once-a-day schedule and highest on the thrice-daily schedule. The possible interpretations and general consequences of these findings are discussed. The results reflect the long duration of action of guanfacine and justify the recommendation of low, single daily doses averaging 2-3 mg for long-term treatment. They also demonstrate the value of guanfacine monotherapy in the treatment of hypertension.