Title: Cantharidin
CAS Registry Number: 56-25-7
CAS Name: Hexahydro-3a,7a-dimethyl-4,7-epoxyisobenzofuran-1,3-dione
Additional Names: 2,3-dimethyl-7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic anhydride; exo-1,2-cis-dimethyl-3,6-epoxyhexahydrophthalic anhydride; cantharides camphor
Molecular Formula: C10H12O4
Molecular Weight: 196.20
Percent Composition: C 61.22%, H 6.16%, O 32.62%
Literature References: Defensive toxin produced by blister beetles of the family Meloidae. Active principle of cantharides, q.v. and notorious "Spanish Fly" aphrodisiac. Synthesis and stereochemistry: Woodward, Loftfield, J. Am. Chem. Soc. 63, 3167 (1941); Ziegler et al., Ann. 551, 1 (1942). Stereospecific synthesis: Stork, Van Tamelen et al., J. Am. Chem. Soc. 75, 384 (1953). Simple efficient synthesis: W. G. Dauben et al., ibid. 102, 6893 (1980). Crystal structure: M. Zehnder, U. Thewalt, Helv. Chim. Acta 60, 740 (1977). Review of biological source and medicinal uses: L. Moed et al., Arch. Dermatol. 137, 1357-1360 (2001).
Properties: Orthorhombic plates, scales, mp 218°. Sublimes at about 110° (12 mm Hg, 3-5 mm distance). Insol in cold water, somewhat sol in hot water. One gram dissolves in 40 ml acetone, 65 ml chloroform, 560 ml ether, 150 ml ethyl acetate. Sol in oils.
Melting point: mp 218°
CAUTION: Extreme irritant and vesicant. Direct contact may cause intense blister formation. Potential symptoms of overexposure are burning sensation of throat and oral cavity; diarrhea, hemorrhagic necrosis of upper GI tract, abdominal pain; urinary urgency, strangury, hematuria, priapism, oliguria, tubular necrosis, renal failure. See Clinical Toxicology of Commercial Products, R. E. Gosselin et al., Eds. (Williams & Wilkins, Baltimore, 5th ed., 1984) Section II, 270.
Therap-Cat: Vesicant; in treatment of warts and molluscum.
Therap-Cat-Vet: Rubefacient, vesicant, counterirritant.
Capobenic Acid Capravirine Caprenin Capreomycin Caproic Aldehyde

Cantharidin structure.png
CAS number 56-25-7 N
ChemSpider 2297293 YesY
KEGG C16778 N
Jmol-3D images Image 1
Molecular formula C10H12O4
Molar mass 196.20 g/mol
Density 1.41 g/cm³
Melting point 212 °C
GHS pictograms The skull-and-crossbones pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
EU classification Very Toxic T+
R-phrases R28-R36/37/38
S-phrases S53-S45
Main hazards Highly toxic
NFPA 704
NFPA 704.svg
LD50 0.03–0.5 mg/kg (human)
 N (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Cantharidin, a type of terpenoid, is a chemical compound secreted by many species of blister beetle, and most notably by the Spanish fly, Lytta vesicatoria. The false blister beetles, cardinal beetles and soldier beetles also produce cantharidin. It is a poisonous substance, acting as a blister agent, and can cause severe chemical burns, but these same properties make it effective as a topical medication.