Chlorpromazine and related antipsychotic tricyclic compounds competitively inhibit the interaction between tumor-promoting phorbol esters and their specific receptors.

Various antipsychotic and antidepressant drugs have been tested for their effects on the binding of [3H] phorbol-dibutyrate (PDBu) to its specific receptor. Chlorpromazine and related antipsychotic tricyclic compounds competitively inhibit the interaction between tumor-promoting phorbol esters and their specific receptors. The relative potency of drugs in competing for [3H]PDBU to receptors is fluphenzine greater than flupenthioxal greater than 2-chloroimipramine greater than chlorpromazine greater than imipramine. The significance of these findings is discussed with special reference to the potential tumor-promoting activity of these drugs.