Practolol Disopyramide

Cumming AD, Robertson C. Interaction between disopyramide and practolol. BMJ 1979 2(6200) 1264. 

Harrison, P.M. Tonkin, A.M. McLean, A.J. Simple and rapid analysis of atenolol and metoprolol in plasma using solid-phase extraction and high-performance liquid chromatography. J.Chromatogr, 1985, 339, 429-433 [plasma SPE fluorescence detection LOD 10 ng/mL non-interfering chlorothiazide, disopyramide, furosemide, hydralazine, lidocaine, methydopa, prazosin, verapamil simultaneous alprenolol, oxprenolol, pindolol, practolol, propranolol, timolol]... 

Two patients with supraventricular tachycardia (180 bpm) were treated, firstly with intravenous practolol (20 and 10 mg respectively) and shortly afterwards with disopyramide (150 and 80 mg respectively). The first patient rapidly developed sinus bradycardia of 25 bpm, lost consciousness and became profoundly hypotensive. He did not respond to 600 micrograms of atropine, but later his heart rate increased to 60 bpm while a temporary pacemaker was being inserted. He was successfully treated with disopyramide 150 mg alone for a later episode of tachycardia. The second patient also developed severe bradycardia and asystole, despite the use of atropine. He was resuscitated with adrenaline (epinephrine) but later died. ... 

Severe bradycardia has been reported in another patient, similarly treated with intravenous practolol and then disopyramide. Another patient developed severe bradycardia and died when treated for supraventricular tachycardia with pindolol 5 mg and disopyramide 250 mg (both orally). Another patient l ng oral disopyramide 250 mg twice daily developed asystole when given a total of 60 mg of intravenous sotalol. ... 

The general cliitical importance of this interaction is uncertain. A clear risk seemed to exist in patients who were treated with disopyramide and practolol. Considerable caution should be exercised in patients treated... 

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