This section is from the book "A Practitioner's Handbook Of Materia Medica And Therapeutics", by Thos. S. Blair. Also available from Amazon: A Practitioner's handbook of Materia Medica and Therapeutics.
Cantharis. An irritant diuretic and aphrodisiac. Externally used as a rubefacient and vesicant. In very small doses it is much employed by sectarian and somewhat by regular physicians in cystitis, irritable bladder, and nephritis, but we have so much better remedies that it must be considered as of secondary importance except in relaxation of the bladder walls. Cantharidin has been recommended in lupus and tuberculosis. (Tr., 1/4 to 10 I Merck's cantharidin in I to 100,000 solution, using 1% alcohol in 99% water as solvent, and giving 5 to 40 I doses, well diluted.)