Effects of Persantin (RA8), a new coronary vasodilator, on coronary blood flow and cardiac dynamics in the dog.

• In 1951, Fischer and Roch made available an entirely new class of compounds which were basically a double-ring structure consisting of two condensed pyrimidine rings. Immediately following the introduction of this group of compounds, numerous derivatives from this pyrimido-(5, 4-d)-pyrimidine series were synthesized, and certain ones were demonstrated to possess interesting properties worthy of clinical evaluation. One of these compounds, Persantin (RA8) (fig. 1), was shown by Kadatz to have significant effects on coronary blood flow. Since this time, much interest has been stimulated by various investigators in evaluating the ability of this compound to improve coronary blood flow. In experiments performed on normal dogs, Persantin increased the coronary blood flow as much as 123 per cent as determined by the bubble flowmeter, 90 per cent with the Thermostromuhr of Rein, and 35 per cent with the nitrous-oxide method of Kety and Schmidt. Bretschneider et al., using the Stromuhr catheter of Kanzow, reported flow increases up to 400 per cent with a 200 per cent increase persisting for 10 minutes and 100 per cent increases for several hours. In these experiments, papaverine was only half as effective and its duration of action only one-fifth that of Persantin. Theophylline was found to be the least effective agent; the