Chloroquine, quinine, procaine, quinidine and clomipramine are prostaglandin agonists and antagonists.

@article{Manku1976ChloroquineQP,
  title={Chloroquine, quinine, procaine, quinidine and clomipramine are prostaglandin agonists and antagonists.},
  author={Mehar S. Manku and David F. Horrobin},
  journal={Prostaglandins},
  year={1976},
  volume={12 5},
  pages={789-801}
}
Chloroquine, quinine, procaine, quinidine and clomipramine behave as prostaglandin (PG) antagonists in a rat mesenteric vascular bed preparation. The ID50 concentrations were within the range of therapeutically effective human plasma levels in each case. Antagonism to PGE2 was studied in detail and seemed to be at least in part competitive. The drugs also antagonized the effects of PGs A1, A2, F2alpha and E1. Each drug also had weak prostaglandin agonist activity but only over a very narrow… CONTINUE READING