Interaction of carbamazepine and other drugs with adenosine (A1 and A2) receptors.

The tricyclic anticonvulsant carbamazepine (CBZ) is effective in pain and affective disorder, but the mechanism of action for this drug has not been defined. Recently it was reported that CBZ had interaction with adenosine receptor, which is related to the inhibition of release of neurotransmitter. In the present study, we investigated the in vitro effects of CBZ and other drugs upon adenosine receptor binding using 3H-L-phenylisopropyladenosine (A1) and 3H-N-ethylcarboxamidoadenosine (A2). The following results were obtained: CBZ and its derivative oxcarbazepine inhibit 3H-PIA binding at therapeutic plasma level (20-30 microM) more than they inhibit 3H-NECA binding; Theophylline and caffeine, methylxanthines, which are adenosine antagonists, inhibit both bindings; Other anticonvulsants such as phenobarbital, phenytoin and valproate and still other psychotropic drugs such as diazepam, imipramine and chlorpromazine have little or no effect on both bindings. These findings suggest that anticonvulsive and sedative effects of CBZ and its derivatives appear due to action on adenosine receptors (A1 and partially A2) at the therapeutic level and methylxanthines have stimulant and convulsant effects due to occupation on both A1 and A2 adenosine receptors.