CENTRAL α2‐ADRENOCEPTORS AND BLOOD PRESSURE REGULATION IN MAN: STUDIES WITH GUANFACINE (BS100‐141) AND AZEPEXOLE (BHT 933)

The haemodynamic and sedative actions of guanfacine and azepexole, two α2 adrenoceptor agonists, have been examined in hypertensive patients and normotensive subjects, respectively. After oral dosing both drugs lowered supine and erect blood pressure, reduced plasma noradrenaline and caused subjective drowsiness lasting for 6–8 h. The duration of hypotensive action of a single dose of guanfacine was 24–30 h allowing single daily dosing in several patients, while the duration of effect of azepexole was shorter (8 h). After 8–10 weeks treatment with guanfacine was stopped. There was a gradual return of blood pressure to pre‐treatment levels over 4 days. Both the sedative effect and the centrally mediated fall in blood pressure appear to result from activation of adrenoceptors of the α2 subtype.