Cutaneous leishmaniasis is not a threat to the health of the world, but the protozoan parasite which causes it is not too distantly related to the parasites of malaria. An agent effective against Leishmania could, more significantly, lead to assault on malaria. The communication by Peña Chavarría in this issue (p 1142) documents his experience in treating cutaneous leishmaniasis with cycloguanil pamoate suspended in a mixture of benzyl benzoate and castor oil. This focuses upon a striking example of drug development which has been largely neglected, the influence of the physical state of a drug on its effectiveness.
The structural formula used by Peña Chavarría resulted from the problem of how to make a compound—known to be active in minute concentrations against malarial parasites—available on a continuous basis as a plasma solute. A therapeutically effective level was needed without incurring the risk of folic acid inhibition. The absorption of the