AN OVERVIEW OF THE METHYLXANTHINES AND THEIR REGULATION IN THE HORSE

Caffeine, theophylline and theobromine are naturally occurring members of the methylxanthine family; pentoxifylline, dyphylline and enprofyl line are structurally related synthetic pharmaceuticals. Caffeine has predominantly central nervous system effects, theophylline, dyphylline and enprofylline have predominantly bronchodilator effects, while the obromine is associated with diuretic responses. Pentoxifylline is thou ght to increase red cell deformability and facilitate bloodflow throug h capillary beds. The methylxanthines are not highly potent agents; th ey are typically administered in gram doses and they tend to have rela tively long plasma half-lives. They remain detectable in plasma and ur ine for relatively long periods. Similarly, traces of the naturally oc curring members of this family are not uncommonly identified in forens ic samples. In this review we report on the defection, actions, uses a nd regulatory control of this group of agents in performance.