The beetle, Cantharis vesicatoria, dried. Hungary.

Characters. - From eight to ten lines long, furnished with two wing-covers of a shining metallic-green colour, under which are two membranous transparent wings; odour strong and disagreeable; powder greyish-brown, containing shining green particles. Free from mites.

Composition. - Cantharidin, a tasteless, inodorous substance, which may be crystallised from an alcoholic extract. It is insoluble in water and cold alcohol, although it may be extracted from the cantharides by both when in conjunction with the yellow colouring-matter. The other ingredients are unimportant.

Preparations.

B.P.

Strength.

Dose.

Acetum Cantharidis .....................................

... 2 oz. to 1 pint ..................................

Charta Epispastica........................................

..............................................................

Emplastrum Calefaciens ..............................

...1 part in 24, nearly...........................

,, Cantharidis...............................

...1 part in 3..........................................

Liquor Epispasticus......................................

...1 oz. to 2 1/2 fl. oz...........................

Tinctura Cantharidis.....................................

... 5 1/2 gr. to 1 fl. oz..........................

5-20 min.

Unguentum ,, .....................................

...1 part to 7, nearly.............................

U.S.P

Ceratum Cantharidis.

,, Extracti Cantharidis. Charta Cantharidis. Collodion cum Cantharide. Linimentum Cantharidis (p. 517). Tinctura Cantharidis.

Action. - Externally the preparations of cantharides produce, when applied to the skin, tingling, redness, and vesication; if the action is prolonged, the vesicles coalesce into a large bleb filled with serum, and if left on too long the true skin becomes irritated, and suppuration, ulceration, and even sloughing occur.

Internally the drug causes irritation of the alimentary canal, with a feeling of warmth in the mouth, oesophagus, and stomach, loss of appetite, and (if its use be prolonged, or if a single large dose be given) burning and pain in the stomach (increased by pressure), nausea, vomiting, and diarrhoea (the vomited and ejected matters often being mixed with blood).

It affects the trachea and larger bronchi, causing congestion and irritation.

It affects the kidneys and urinary passages, causing pain in the loins, burning in the bladder and along the urethra, irritation of the glans penis, and sometimes increased sexual appetite. If continued for a long time, it causes great pain in the kidneys, painful erections of the penis, difficulty of micturition or suppression of urine, the latter often containing albumen or blood.

The nervous system is usually not affected by small doses, but large doses cause headache and quickened pulse and respiration.

Very large doses produce insensibility, paralysis of respiration, and death with asphyxial convulsions.

The salivary glands and the back of the throat become so much swollen that swallowing is difficult, and the attempt to swallow may give rise to convulsions, like hydrophobia.

Urinary Organs. - The inflammation caused by cantharides begins in the glomeruli, and not in the straight tubes as is often stated.

The first condition of the kidneys noticed after the administration of cantharides is extravasation of leucocytes into the glomeruli and an exudation of a fibrinous matrix; next, following in order, we notice : (1) The glomeruli and the proximate tubules are filled with a granular fluid.

(2) The cells of the capsule become swollen.

(3) The cells of the collecting tubes are affected, and become swollen.

(4) The cells of the whole urinary tubule become swollen.

(5) In the straight collecting tubes the cells become multiplied, and are thrown off so that the lumen becomes full of exuded cells.

Treatment in Poisoning. - Evacuate the stomach, give mucilaginous drinks to lessen the gastro-intestinal irritation, but avoid oils or fats, which increase the solubility of cantharidin and the dangers arising from its absorption. Use opium and sitz-baths to relieve the strangury.

Uses.- It is used externally as an irritant and counter-irritant, and internally for its effect on the genito-urinary tract.

Externally as irritant (1) To increase the supply of blood to a part, and hence improve its nutrition, as in chronic ulcers in the leg.

(2) To cause disappearance of inflammatory products in chronic inflamed joints and swellings; also in acutely inflamed joints, as in acute rheumatism, in the form of a blister above and below the joint. In chronic rheumatism a large and strong blister should be used.

As counter-irritant it is used in pleurisy and pneumonia, and often relieves the pain almost immediately.

It is also used in acute inflammation of the heart and pericardium. It is better not to apply the blister directly over the affected part, but a little to one side, since there is a risk of getting the vessels just underneath it congested instead of anemic.

In affections of other serous membranes, as in meningitis, and often in inflammation of the brain itself, the application of a blister is very useful.

applied. Front view.

Fig. 226.   Diagram of the body showing some of the points where blisters or sinapisms are usually

Fig. 226. - Diagram of the body showing some of the points where blisters or sinapisms are usually

When applied to the nape of the neck, it often relieves giddiness and disturbed cerebral functions dependent on tertiary syphilis, diseases of the ear, or of the semicircular canals.

It is occasionally useful to keep up the irritation by means of savine ointment applied to the blistered surface.

It is also locally applied to the perineum in inflammation' of the prostate, and over the tender region in inflammation of the ovary.

A blister sometimes relieves the pain of sciatica and the tenderness of nerves in peripheral paralysis;. and a blister the size of a shilling may be applied over each tender spot in these diseases. In sciatica a row of such small blisters, or a long narrow blister along the course of the nerve, is sometimes better than single small blisters. A blister is a useful application applied under the ear in paralysis of the facial nerve due to cold.

Internally, in small doses of 1 or 2min. of tincture, it checks haematuria; in larger doses it increases the disease.

In Bright's disease, after the acute stage has passed, but a little albumen and blood still remain in the urine, it is very useful in doses of 1-3 min. every three hours.

Order Coleoptera Cantharis B and U S P Cantharides 327

Fig. 227. - Diagram, like Fig. 226. Back view.

In cystitis, especially where there is inability to retain the urine, and also in ordinary incontinence of urine, it is useful; though in both cases atropine generally acts better.

A drop of tincture three times a day will often relieve hordee.

Precautions. - (1) Do not use the blisters on debilitated persons, and children; or do not keep them on long, but just sufficient to start the blister, and then, after two or three hours, put on a poultice to make the blister rise.

(2) Be careful of its use both externally and internally in Bright's disease.