The effects of dyphylline [7-(2,3-dihydroxypropyl) theophylline] on the toxicity of hycanthone on the frog's heart.

The effects of the topical application of Dyphylline in concentrations of 1.0 mg/1.0 ml and 10 mg/1.0 ml Ringer's solution and 25 mg/1.0 ml, 0.065% NaCl solution (the content of ampoules in clinical use) were investigated on frog's heart in situ. Dyphylline in all of the above concentrations had a stimulatory effect on the frog's heart. Hycanthone methanesulphonate in concentration of 1.0 ml/1.0 ml when topically applied to the frog's heart had a depressant effect on both of the contractility and rhythmicity. The depressant effects of Hycanthone in concentration of 1:1 were compared before and after the topical application of Dyphylline in the above mentioned concentrations. It was found that Dyphylline in concentration of 1.0 mg/1.0 ml could partially antagonize the depressant effect of Hycanthone on the heart rate but not on the force of contraction. Dyphylline in concentration of 10 mg/1.0 ml could partially antagonize the depressant effects of Hycanthone on both of the heart rate and the force of contraction. Dyphylline in concentration of 25 mg/1.0 ml could completely antagonize the depressant effects of hycanthone on both of the heart rate and the force of contraction.