title: Comparative efficacies and durations of action of phenoxybenzamine, verapamil/nitroglycerin solution, and papaverine as topical antispasmodics for radial artery coronary bypass grafting.
abstract: OBJECTIVE
  Radial arteries are increasingly used as conduits for coronary artery bypass grafts, but perioperative graft vasospasm continues to be a concern. Phenoxybenzamine, verapamil/nitroglycerin solution, and papaverine have been advocated as topical antispasmodic agents. We compared the relative efficacies and durations of action of these agents.
  
  
  METHODS
  Isometric tension developed in response to clinically important vasoconstrictors was measured in 100 radial artery rings (from patients undergoing coronary artery bypass grafting, n = 25) after 15 minutes of ex vivo incubation with phenoxybenzamine, verapamil/nitroglycerin solution, papaverine, or vehicle (control). Duration of action was assessed by measuring responses to vasoconstrictors in antispasmodic pretreated and control rings at intervals through 5 hours.
  
  
  RESULTS
  Verapamil/nitroglycerin solution reduced vasoconstriction in response to epinephrine, angiotensin II, prostaglandin F(2alpha), and phenylephrine but its effect had almost completely waned after 5 hours. Phenoxybenzamine prevented vasoconstriction in response to epinephrine, dopamine, and phenylephrine, with its effect lasting at least 5 hours. Papaverine had limited antispasmodic efficacy and prevented vasoconstriction in response to potassium (60 mmol/L) and phenylephrine for only 1 hour at the longest.
  
  
  CONCLUSIONS
  Verapamil/nitroglycerin solution has a broad efficacy against a range of vasoconstrictors but a limited duration of action. Papaverine has the shortest duration of action. Phenoxybenzamine is an effective agent with a prolonged duration of action, specifically preventing catecholamine mediated vasospasm of radial artery conduits.
authors.affiliation: Department of Cardiothoracic Surgery, John Radcliffe Hospital, University of Oxford, United Kingdom.
authors.forename: Shafi
authors.initials: S
authors.lastname: Mussa
authors.forename: Tomasz J
authors.initials: TJ
authors.lastname: Guzik
authors.forename: Edward
authors.initials: E
authors.lastname: Black
authors.forename: Michelle A
authors.initials: MA
authors.lastname: Dipp
authors.forename: Keith M
authors.initials: KM
authors.lastname: Channon
authors.forename: David P
authors.initials: DP
authors.lastname: Taggart
mesh_terms: D000287:Administration, Topical; D001026:Coronary Artery Bypass; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D005996:Nitroglycerin / Q000008:administration & dosage; D010208:Papaverine / Q000008:administration & dosage; D010276:Parasympatholytics / Q000008:administration & dosage*; D010643:Phenoxybenzamine / Q000008:administration & dosage; D017534:Radial Artery / Q000187:drug effects* / Q000502:physiology; D012996:Solutions; D014661:Vasoconstriction / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014665:Vasodilator Agents / Q000008:administration & dosage* / Q000494:pharmacology; D014700:Verapamil / Q000008:administration & dosage
chemical_list: D010276:Parasympatholytics; D012996:Solutions; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D010643:Phenoxybenzamine; D014700:Verapamil; D010208:Papaverine; D005996:Nitroglycerin