Chrysarobinum, B.P. Chrysarobin.
Related entry: Araroba
Chrysarobin, as generally found in pharmacy, is a mixture of substances obtained from araroba by extracting with hot chloroform, evaporating to dryness, and powdering. The synonym chrysophanic acid, a name by which it is very generally known, is a misnomer, since the substance consists of chrysarobin (C30H26O7), (Chrysarobinum, U.S.P.), dichrysarobin, and dichrysarobin methyl-ether. Chrysarobin occurs as a yellow micro-crystalline, odourless, tasteless powder, which has an irritating effect on the mucous membranes and especially the conjunctiva. On heating it melts, giving off yellow vapours, and on complete ignition leaves not more than 1 per cent. of ash.
Slightly soluble in water and in ether; entirely soluble in hot chloroform and fats, and almost entirely in hot alcohol; partially soluble in petroleum spirit, and in solutions of alkalies with brown colouration.
Action and Uses.—Chrysarobin has been given internally in psoriasis and chronic skin diseases, but is rarely so employed, since it readily causes gastroenteritis. A small quantity is absorbed and colours the urine yellow, which changes to red on the addition of an alkali. It is best administered in a pill made with glycerin of tragacanth. Externally Pigmentum Chrysarobini and Unguentum Chrysarobini are commonly used in psoriasis, alopecia, ringworm of the scalp, and other parasitic affections of the skin. The former is a cleanly application by which the drug is brought into close contact with the skin over a long period. The ointment, which should not be applied over a large surface, is often required to be diluted. It stains the skin and linen; such stains may be removed by a solution of chlorinated lime. Plasters are prepared of various strengths. Oxidised chrysarobin was formerly recommended by Unna for use in ointments as a substitute for chrysarobin; it is darker in colour and is much less irritating. Recent researches seem to show that the action of chrysarobin is dependent upon an oxidising process taking place upon the skin in which the oleic acid secreted by the sweat and sebum glands is concerned. Ointment of lead oleate is suggested as the best basis. Derivatives of chrysarobin similarly used are anthrarobin, a reduction product of alizarin, chrysarobin triacetate (Eurobin), and chrysarobin tetra-acetate (Lenirobin).
Dose.—½ to 6 centigrams (1/10 to 1 grain).
- Pigmentum Chrysarobini, B.P.C.—CHRYSAROBIN PAINT. 1 in 10.
- Applied to the skin with a stiff brush in chronic psoriasis. It has the advantage over chrysarobin ointments of not staining the linen.
- Unguentum Chrysarobini, B.P.—CHRYSAROBIN OINTMENT.
- Chrysarobin, 4; benzoated lard, 96. Mix the chrysarobin gradually with the previously melted lard, heat gently until it is dissolved, and stir till cold. The chrysarobin is not usually entirely soluble, and the insoluble portion should be strained out. Chrysarobin ointment is applied to the patches in chronic psoriasis. Diluted with 2 to 4 parts of benzoated lard it is used in chronic eczema, acne, and other skin affections. Chrysarobin ointment stains the hair, skin, and linen. It should not be applied over large surfaces.
- Unguentum Chrysarobini, U.S.P.—CHRYSAROBIN OINTMENT.
- Chrysarobin, 6; benzoinated lard, 94.
- Unguentum Chrysarobini Compositum, B.P.C.—COMPOUND CHRYSAROBIN OINTMENT.
- Chrysarobin, 5; ammonium ichthosulphonate, 5; salicylic acid, 2; soft paraffin, yellow, 88.