Almokalant is a newly developed selective blocker of the delayed outward K+ current and exhibits the electrophysiological properties of a class III antiarrhythmic agent. In a Scandinavian multicenter, placebo-controlled trial, the antiarrhythmic efficacy of
almokalant was investigated in patients with
paroxysmal supraventricular tachycardia: 87 patients with mean age of 50 +/- 14 years (range 21-71 years), with
reciprocating tachycardia due to either Wolff-Parkinson-White (
WPW) syndrome (n = 58) or
atrioventricular nodal reentry tachycardia (AVNRT) (n = 29) were studied with transesophageal atrial stimulation. After a baseline procedure, during which sustained
tachycardia was induced and overdrive terminated,
tachycardia was reinduced and an intravenous (i.v.) infusion of either placebo or
almokalant (aiming at a pseudoequilibrium plasma level of 20, 50, 100, or 150 nM) (Cpl 20-Cpl 150), was administered. Each patient was studied at two Cpl. Thirty-nine patients were randomly assigned in a double-blind fashion to either placebo+almokalant at Cpl 20 or Cpl 20 + Cpl 50; 26 patients were studied openly at Cpl 50 + Cpl 100, and 22 were studied openly at Cpl 100 + Cpl 150
almokalant. The antiarrhythmic efficacy was assessed as the ability to terminate induced
tachycardia and to suppress inducibility: The proportion of patients in which the
tachycardia was terminated was placebo 3 of 20 (15%); Cpl 20, 7 of 36 (19%): Cpl 50, 10 of 36 (28%); Cpl 100, 14 of 35 (40%); and Cpl 150, 5 of 9 (56%).(ABSTRACT TRUNCATED AT 250 WORDS)