Cyclic adenosine 3', 5'-monophosphate and the mechanism of action of three common anti-inflammatory drugs.

1 The effects of indomethacin, dexamethasone and colchicine on cyclic adenosine 3', 5'-monophosphate (cyclic AMP) concentration in leucocytes during a crystal-induced pleurisy in rats were studied. 2 Each of the drugs significantly increased leucocyte cyclic AMP content within 3 h of the injection of crystals. 3 By 6 h, leucocyte cyclic AMP levels returning toward control levels and could not be sustained at the higher level by an additional administration of the respective anti-inflammatory drug.