title: Clinical electrophysiology of flestolol, a potent ultra short-acting beta blocker.
abstract: We measured the electrophysiologic effects of flestolol, an ultra short-acting beta blocker, in 15 patients at two infusion rates: a 45 micrograms/kg loading dose followed by a 5 micrograms/kg/min infusion and a 60 micrograms/kg loading dose followed by a 10 micrograms/kg/min infusion. Electrophysiologic measurements were made after 15 minutes at each infusion rate (plasma concentrations 46 +/- 11 and 94 +/- 23 ng/ml). Flestolol produced dose-dependent effects on the sinus node, the atrioventricular (AV) node, and right ventricular refractoriness, whereas atrial refractoriness and infranodal conduction were unchanged. At the 10 micrograms/kg/min dose, flestolol prolonged sinus cycle length by a mean of 20% (p = 0.0001), corrected sinus node recovery time by 42% (p = 0.02), AH interval by 21% (p = 0.0001), AV node effective refractory period by 28%, AV node Wenckebach cycle length by 30% (0.0001), and right ventricular effective refractory period by 5% (p = 0.03). A significant concentration-effect relationship (p less than or equal to 0.03) was present for all variables which had significant dose-effect relationships. No patient developed hypotension, bradyarrhythmias, or other toxicity. Sinus cycle length decreased linearly with time in the post infusion period (r = 0.99); by 30 minutes post infusion, measured electrophysiologic variables had returned to control values and flestolol plasma concentration had decreased to 4 +/- 2 ng/ml. Flestolol's electrophysiologic effects are similar to those of other beta blockers. In doses up to 10 micrograms/kg/min, it is safe in selected patients, has rapid onset and offset of action, and does not cause acute rebound.
authors.forename: C D
authors.initials: CD
authors.lastname: Swerdlow
authors.forename: J
authors.initials: J
authors.lastname: Peterson
authors.forename: P
authors.initials: P
authors.lastname: Turlapaty
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use*; D000328:Adult; D000368:Aged; D001283:Atrioventricular Node / Q000503:physiopathology; D004562:Electrocardiography; D004594:Electrophysiology; D005260:Female; D005464:Fluorobenzenes; D006329:Heart Conduction System / Q000503:physiopathology; D006331:Heart Diseases / Q000188:drug therapy / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009431:Neural Conduction; D011412:Propanolamines / Q000009:adverse effects / Q000378:metabolism / Q000627:therapeutic use*; D011930:Reaction Time; D012849:Sinoatrial Node / Q000503:physiopathology; D013997:Time Factors
chemical_list: D000319:Adrenergic beta-Antagonists; D005464:Fluorobenzenes; D011412:Propanolamines; C047847:flestolol