title: Effect of transition from sitaxsentan to ambrisentan in pulmonary arterial hypertension.
abstract: BACKGROUND
  Currently available endothelin receptor antagonists for treating pulmonary arterial hypertension block either the endothelin (ET) receptor A or both A and B receptors. Transition from one endothelin receptor antagonist to another may theoretically alter side-effects or efficacy. We report our experience of a transition from sitaxsentan to ambrisentan, both predominant ET(A) receptor antagonists, in pulmonary arterial hypertension patients.
  
  
  METHODS
  At Baylor Pulmonary Hypertension Center, 18 patients enrolled in the open-label extension phase of the original sitaxsentan studies (Sitaxsentan To Relieve ImpaireD Exercise) were transitioned to ambrisentan (from July 2007 to September 2007) at the time of study closure. Pre-transition (PreT), 1 month (1Mth) and 1 year (1Yr) post-transition assessments of 6-minute walk distance (6MWD), brain naturetic peptide (BNP) levels, WHO functional class (WHO FC), Borg dyspnea score (BDS), oxygen saturation, liver function, and peripheral edema were compared.
  
  
  RESULTS
  6MWD was 356 ± 126 m at PreT, 361 ± 125 m at 1Mth, and 394 ± 114 m at 1Yr (mean ± SD). There was no difference in the walk distance at 1Mth and 1Yr post transition compared with PreT (P=0.92, 0.41 respectively). Oxygen saturation was no different at 1Mth and 1Yr to PreT level (P=0.49 and P=0.06 respectively). BNP was 178 ± 44 pg/mL at PreT, 129 ± 144 pg/mL at 1Mth and 157 ± 201 at 1Yr. Peripheral edema was present in 7/18 patients at PreT, in 8/16 patients at 1Mth, and in 6/13 patients at 1Yr post transition. Proportions of patients with edema over these 3 time points did not change significantly (P=0.803). At 1Yr, 2 patients had died, 1 had undergone lung transplantation, 1 had relocated, and 1 patient was started on intravenous prostacyclin therapy. Over 3 points (baseline, 1 month, and 1 year), there was no significant change in function class (P=0.672).
  
  
  CONCLUSIONS
  Our limited data suggest that ET(A) receptor antagonists can be switched from one to another with sustained exercise capacity and maintained WHO FC with no increase in incidence of peripheral edema.
authors.affiliation: Division of Pulmonary-Critical Care Medicine, Baylor College of Medicine, Houston, Texas, USA. safdar@bcm.edu
authors.forename: Zeenat
authors.initials: Z
authors.lastname: Safdar
mesh_terms: D000328:Adult; D000368:Aged; D000959:Antihypertensive Agents / Q000008:administration & dosage* / Q000009:adverse effects; D001794:Blood Pressure / Q000187:drug effects; D057915:Drug Substitution; D004417:Dyspnea / Q000209:etiology; D004487:Edema / Q000209:etiology; D065130:Endothelin A Receptor Antagonists; D005080:Exercise Test; D017079:Exercise Tolerance / Q000187:drug effects; D065627:Familial Primary Pulmonary Hypertension; D005260:Female; D006801:Humans; D006976:Hypertension, Pulmonary / Q000097:blood / Q000150:complications / Q000188:drug therapy / Q000503:physiopathology; D007555:Isoxazoles / Q000008:administration & dosage* / Q000009:adverse effects; D008111:Liver Function Tests; D008297:Male; D008875:Middle Aged; D020097:Natriuretic Peptide, Brain / Q000097:blood; D010100:Oxygen / Q000097:blood; D010666:Phenylpropionates / Q000008:administration & dosage* / Q000009:adverse effects; D011724:Pyridazines / Q000008:administration & dosage* / Q000009:adverse effects; D012189:Retrospective Studies; D013781:Texas; D013876:Thiophenes / Q000008:administration & dosage* / Q000009:adverse effects; D013997:Time Factors; D016896:Treatment Outcome; D016138:Walking
chemical_list: D000959:Antihypertensive Agents; D065130:Endothelin A Receptor Antagonists; D007555:Isoxazoles; D010666:Phenylpropionates; D011724:Pyridazines; D013876:Thiophenes; D020097:Natriuretic Peptide, Brain; C467894:ambrisentan; C106276:sitaxsentan; D010100:Oxygen