some agents ( e.g . zk 62 711 , ici 63,197 , ro 20 -- 1724 , dipyridamol ) were considerably more potent as inhibitors of cyclic amp than of cyclic gmp hydrolysis , while other agents ( m & b 22.948 and dilazep ) selectively inhibited cyclic gmp breakdown , and some ( theophylline , papaverine , ibmx and sq 20,006 ) showed little selectivity .
C0039771
theophylline
C0000096
ibmx