Although propentofylline is a derivative of the same heterocyclic ring system
(1,3,7-trisubstituted xanthines), its mechanisms of action differ considerably from
those of the classical natural methylxanthines: theophylline and caffeine, and of pentoxyfylline,
to which it bears a close structural resemblance (Table 1). The divergent
profiles can be summarized according to the rank order of decreasing potency (approximate
active concentration shown in brackets) as follows: propentofylline: adeno-