Effect of sodium cyanate on Plasmodium falciparum in vitro.

Sodium cyanate at concentrations as low as 0.5 mM inhibited the growth of Plasmodium falciparum (FCR-3 Strain) utilizing the Trager-Jensen continuous culture system. At concentration higher than 1 mM, the parasites were irreversibly destroyed. Utilizing synchronized cultures, the relative susceptibilities of early and late trophozite forms were examined, and it was found that both developmental forms were equally susceptible to the action of cyanate. Pretreatment of red cells with sodium cyanate prior to infection did not alter the intracellular growth of the parasite. Consequently, the effect of the drug is likely to be on the parasite per se rather than the red cell. The mechanism of action is probably the carbamylation of essential, parasite proteins that eventually impair growth and/or function. Published pharmacological studies in humans would predict that the level of cyanate at which growth inhibition occurs in vitro can be achieved in vivo and that the adverse effects will likely be minimal for short treatment periods.