Related entry: Cantharides
C10H12O4 = 196.096.
Cantharidin, C10H12O4, the anhydride, or lactone, of cantharidic acid, is obtained from Cantharis vesicatoria and other blistering beetles. It may be obtained by digesting powdered cantharides, 1000, with a mixture of concentrated sulphuric acid, 20, and acetic ether, 1500, for two days at ordinary temperature, then mixing with barium carbonate, 40, and exhausting the mixture with acetic ether. The latter is distilled off and the residue set aside for some days for the cantharidin to crystallise out, when it is covered with petroleum ether (specific gravity, 0.740), 200, and gently warmed, to dissolve the fat. The solution is filtered, and the cantharidin washed with petroleum ether and recrystallised from hot alcohol. It occurs in odourless, tasteless, white, rectangular prisms or scales. Melting-point, 218°. It will sublime at a temperature of about 120°.
Very slightly soluble in water, sparingly soluble in alcohol; soluble in ether (1 in 700), acetic ether (1 in 150), chloroform (1 in 65), acetone (1 in 46), glacial acetic acid, or almond oil (1 in 1000). It dissolves in solution of sodium or potassium hydroxides, with the formation of a cantharidate of the base. From these solutions, however, the addition of acids causes re-precipitation of cantharidin.
Action and Uses.—Solutions of cantharidin are used in place of corresponding preparations of cantharides as being more uniform in strength, and more cleanly in application. A solution of cantharidin for internal use may contain 1 milligram (1 grain) dissolved in 2 mils (30 minims) of absolute alcohol with water to make 100 mils (3 ⅓ fluid ounces). This is equivalent to 1 in 100,000 of cantharidin. Potassium and sodium cantharidates are prepared for hypodermic injection by dissolving cantharidin in the corresponding alkali hydroxide; they are used in tuberculosis, lupus and pityriasis rubra (see Liebreich's solution below). In cases of poisoning by cantharidin, emetics should be given and the stomach-pump used, followed by mucilaginous drinks, with ice, camphor, and opium; oils and fats should be avoided.
Dose.—¼ to ½ milligram (1/240 to 1/120 grain).
- Acetum Cantharidini, B.P.C.—VINEGAR OF CANTHARIDIN. 1 in 2000.
- Recommended for use instead of Acetum Cantharidis, because of its uniform strength.
- Collodium Cantharidini, B.P.C.—CANTHARIDIN COLLODION. 3.4 in 1000.
- May be used instead of Collodium Vesicans, which is not uniform in strength.
- Emplastrum Cantharidini, B.P.C.—CANTHARIDIN PLASTER. 1 in 500.
- This plaster is more suitable for blistering purposes than cantharides plaster, as it is more certain in its action.
- Emplastrum Cantharidini Calefaciens, B. P.C.—WARMING CANTHARIDIN PLASTER. 1 in 5000.
- This preparation, which is uniform in composition, may be used with advantage instead of Emplastrum Calefaciens.
- Emplastrum Cantharidini Mite, B.P.C.—MILD CANTHARIDIN PLASTER. 1 in 1000.
- Lotio Cantharidini, B.P.C.—CANTHARIDIN LOTION. Syn.—Lotio Crinalis Stimulans; Stimulating Hair Lotion. 1 in 5000.
- This preparation is used as a stimulating lotion for the scalp. It may be further diluted with alcohol when required for sensitive skins. The head should be washed after a few applications.
- Solutio Cantharidini (Liebreich).—LIEBREICH'S CANTHARIDIN SOLUTION.
- Cantharidin, 0.02; potassium hydroxide, 0.04; distilled water, 100. Dose.—5 decimils (0.5 milliliters) (8 minims).
- Tinctura Cantharidini, B.P.C.—TINCTURE OF CANTHARIDIN. 1 in 10,000.
- This preparation has been suggested as an alternative to Tinctura Cantharidis, because it yields a product of more uniform strength. Dose.—3 to 10 decimils (0.3 to 1.0 milliliters) (5 to 15 minims); if frequently repeated, 1 to 3 decimils (0.1 to 0.3 milliliters) (2 to 5 minims).
- Unguentum Cantharidini, B.P.C.—CANTHARIDIN OINTMENT. 1 in 3000.
- This ointment is more uniform in strength than Unguentum Cantharidis, and is employed similarly.