Acetaminophen; Caffeine; Magnesium Salicylate; Phenyltoloxamine: (Major) Methylxanthines, through antagonism of adenosine and thus pharmacologic-induced coronary vasodilation, have been associated with false-negative results during dipyridamole-thallium 201 stress testing. This medicineВ is onlyВ available on prescription. Monitor with digoxin, phenytoin, warfarin. This may be related to diminished liver metabolism in premature babies. Our doctors will review your order and issue your prescription. Entecavir: (Moderate) Both entecavir and trimethoprim are secreted by active tubular secretion.