title: Lack of tolerance development after long-term administration of the partial beta-adrenoceptor agonist xamoterol.
abstract: Xamoterol is a selective partial beta-adrenoceptor agonist. In a double-blind randomized placebo-controlled study, 30 patients (1 female, 29 male) with mild to moderate heart failure were treated with 200 mg of xamoterol twice daily or placebo during 3 months. At baseline and 72 h after the last tablet intake, the hemodynamic and humoral effects of a single intravenous dose of xamoterol (0.2 mg/kg) were assessed by right heart catheterization. At baseline, intravenous xamoterol raised resting heart rate by 3% (NS) in the placebo and by 6% (NS) in the xamoterol group. On exercise, heart rate was reduced by 10% (p = 0.015) and 7% (p = 0.016), respectively. Pulmonary capillary wedge pressure (PCWP) dropped in both groups: at rest by 4 mm Hg (p = 0.0004) in the placebo group and by 6 mm Hg (p = 0.0002) in the xamoterol group; on exercise by 1 mm Hg (NS) in the placebo and by 6 mm Hg (p = 0.0001) in the xamoterol group. Similar changes of all variables were obtained after long-term therapy in both groups. Mean arterial blood pressure, cardiac index and systemic vascular resistance did not change importantly. Norepinephrine levels did not change, but plasma renin activity decreased at baseline as well as after long-term therapy in both groups by similar amounts. Thus, no signs of tolerance development were observed after an oral treatment with 200 mg of xamoterol twice daily during 3 months. However, xamoterol as a partial agonist exerted only weak changes of cardiac index and PCWP compared to full beta-adrenoceptor agonists. The drug was well tolerated, and serious side effects were absent.
authors.affiliation: Department of Cardiology, University Hospital Eppendorf, Hamburg, FRG.
authors.forename: H H
authors.initials: HH
authors.lastname: Erlemeier
authors.forename: W
authors.initials: W
authors.lastname: Kupper
authors.forename: W
authors.initials: W
authors.lastname: Bleifeld
mesh_terms: D000284:Administration, Oral; D000318:Adrenergic beta-Agonists / Q000009:adverse effects / Q000493:pharmacokinetics / Q000627:therapeutic use*; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D004311:Double-Blind Method; D005260:Female; D006333:Heart Failure / Q000097:blood / Q000188:drug therapy* / Q000503:physiopathology; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D009638:Norepinephrine / Q000097:blood; D011412:Propanolamines / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics / Q000627:therapeutic use*; D011669:Pulmonary Wedge Pressure / Q000187:drug effects; D016032:Randomized Controlled Trials as Topic; D012083:Renin / Q000097:blood; D017307:Xamoterol
chemical_list: D000318:Adrenergic beta-Agonists; D011412:Propanolamines; D017307:Xamoterol; D012083:Renin; D009638:Norepinephrine