Spanish Fly

SPANISH FLY, Litta vesicatoria Fabri-cius (syn. Cantharis vesicatoria L.), an insect of the beetle species (incorrectly called a fly) (see illustration) from the family of blistering beetles, found in the southern and central parts of the Soviet Union and in Southern and Central Europe; it has an elongated, metallic, golden-green body, 1.5-2 cm long and 4-8 mm wide. The collected beetles are dried and stored in well-sealed tins. The active principle of S.F. in the amount of 0.5-1% is cantharidin, C₁₀H₁₂O₄, - * the anhydride of cantharidic acid, C₈H₈O₄(COOH)₂, which is found in S.F. in the sex gland and in the blood partly in free form, partly in the form of alkaline salts; cantharidin is a crystalline substance, volatile even at the temperature of a water bath, melting at t°+214-217°, sparingly soluble in water (1: 30,000), more easily in acidified water; difficult in 90% alcohol (1: 3,300), easily in chloroform, acetone, acetic acid, in fatty and essential oils. Cantharidin has a local irritant effect; on the skin it causes redness, burning, pain and abundant exudation of serous fluid from the vessels of the papillary layer, as a result of which the epidermis rises at the site of action of cantharidin and a blister filled with serous fluid forms, in which cantharidin can be found. If cantharidin acts for a long time, the inflammation takes on a purulent character, and the tissues may undergo necrosis. On mucous membranes, cantharidin acts faster and more sharply than on the skin; powder of S.F., getting into the mouth, nose, throat and intestines, after 2-3 hours causes attacks of severe acute poisoning; blisters appear on the mucous membrane, pain and burning, swallowing is difficult, salivation appears, extreme thirst, vomiting, abdominal pain, diarrhea, often with blood; frequent urges to urinate with an increase in the amount of urine excreted; pains appear in the kidney area, protein, cylinders and blood in the urine, the amount of urine subsequently sharply decreases and anuria sets in; urination becomes painful; in men, a painfully painful erection is observed. The general effect in severe poisoning with cantharidin is manifested by the appearance of severe headaches, clonic and tetanic convulsions, drowsiness, delirium, a drop in pulse, difficulty breathing, cyanosis, cold sweat, cooling of the extremities; on the 4-5th day after the introduction of the poison, death occurs from paralysis of respiration. Assistance in poisoning with S.F. and its preparations - see Poisoning. For humans, the lethal dose of cantharidin is 0.01, and of S.F. powder - 1.5 g; animals have different resistance to cantharidin, resp. S.F.: for dogs the lethal dose of cantharidin is 0.001 per 1 kg of body weight, for chickens - 0.015 per 1 kg, for hedgehogs - 0.03; frogs, however, eat S.F. without any harm to themselves. Cantharidin is excreted through the kidneys with urine, causing inflammatory phenomena throughout the excretory path with symptoms of priapism, often even with external application of S.F. preparations for therapeutic purposes. Therefore, S.F. is now used very rarely for therapeutic purposes and only externally: for neuralgias, e.g. of the sciatic nerve, sometimes for diseases of a rheumatic nature, for inflammations of the eye, pleura and especially for pericarditis, preparations of S.F. are used as a counter-irritant ('flies' on the back of the head or back). Preparations of S.F.: 1) Pulvis Cantharidis, powder of S.F., for preparing all preparations of S.F. Handling of the S.F. powder should be very careful. 2) Emplastrum Cantharidum ordinarium (Ph. VII), ordinary S.F. plaster; used as a local irritant. The plaster is spread on cloth, paper or adhesive plaster and applied to the skin: 3) Emplastrum Cantharidum perpetuum, resinous S.F. plaster; used as the previous one; the effect is more moderate. 4) Collodium cantharidatum (Ph. VII), S.F. collodion, syn. Collodium vesicans, blistering collodion. It is applied directly to the skin, acts like Empl. Canth. ord. 5) Weimar balm (see). 6) T-ra Cantharidis (Ph. VII), tincture of S.F.; the highest dose internally is 0.2 per dose. It was previously used as a diuretic and as an aphrodisiac in impotence; now, when it has been established that the erection after S.F. tincture occurs as a result of irritation of the urethral mucosa by cantharidin, the use of S.F. tincture has been completely abandoned. The tincture is used externally for growing hair on bald spots; the result of treatment is doubtful, therefore the preparation should be considered superfluous. For preparing preparations 'flies' Litta vesicatorianp-n use other cantharidin-containing insects (Meloe, Mylabris).