CANTHARIDES, or SPANISH Fuss, the blister-beetle (q.v.), when prepared for medical use. Their value is due to the presence of a chemical principle, called canthariden, which constitutes from Ys to 1 per cent of cantharides, with the formula CMH„O.. On hydrolysis, this is converted into cantharidic acid, Cs•HmOs. Cantharadin is obtained by treating the pulver ized insects with a solvent, such as alcohol, ether or chloroform (not water), the last being preferable. The solution is evaporated, and the residue is purified from a green oil which ad heres to it obstinately, by digesting with bisul phide of carbon or by redissolving in alcohol. Purification is further affected by animal char coal and the cantharidin crystallized from hot alcohol or chloroform.
Cantharides is used externally for its counter-irritant action. It must be used with discretion especially in cases of older persons, children or paralysis. It must not be used in
renal disease, owing to the risks attendant on absorption. It is administered internally in cases of impotence. Its criminal employment is usually intended to heighten sexual desire, and has frequently led to death. It produces severe frastro-intestinal irritation, and has toxic qual ities, the patient usually dying from arrest of the renal functions. The antidote is the admin istering of bland &lids, such as milk, soda water and plain water, to dilute the poison in the blood.
A number of insects other than cantharides possess the vesicant property, such as the Chinese beetle (Mylabris cichorii) which is especially rich in cantharidin, yielding about twice as much as the cantharides. Our native blister-beetles, when powdered, nearly resemble Mylabris in color, and are used as' adulterants to cantharides.