Xamoterol,a New Selective β-1-Adrenoceptor Partial Agonist,in the Treatment of Postural Hypotension

ABSTRACT. Three patients severely disabled from postural hypotension were treated with xamoterol, a selective β-1-adrenoceptor antagonist with a high degree of partial agonist activity. Oral treatment (200 mg b.i.d.) was chosen on the basis of the effects of acute intravenous administration of xamoterol and pindolol, a non-selective β-adrenoceptor antagonist with partial agonist activity. In these patients pindolol had a predominantly antagonist effect, whereas xamoterol had a predominantly agonist effect after intravenous administration. Oral treatment was carried out with placebo control in a single-blind fashion. The patients reported gradual improvement during the first days of treatment. After 1 month of oral treatment, heart rate had increased by 15 beats/min, systolic blood pressure from 131 to 170 mmHg, diastolic blood pressure from 77 to 91 mmHg and mean blood pressure by 22 mmHg (mean values, supine). During the placebo period (2 weeks) heart rate decreased to pretreatment levels and mean blood pressure was reduced by only 14 mmHg. The patients reported substantial improvement in their condition during active medication. Xamoterol seems to be a useful alternative in the treatment of postural hypotension.