Ammonium bituminosulfonate

Ammonium bituminosulfonate (ichthyol or ichthammol, CAS#) is a product of natural origin obtained in the first step by dry distillation of sulfur-rich oil shale. It is used in medicine as a remedy for treating some forms of skin diseases, such as acne, eczema and psoriasis. It is commonly used in an ointment in 10% or 20% concentrate as a "drawing salve", also called "black ointment". Its dermatological action was discovered by Austrian physician Paul Gerson Unna.

From elementary analysis its composition was calculated to be C28H36S5O6(NH4)2. However, as a product from natural origin it is a mixture of many different compounds.

Chemically, it is a sulfonated shale oil. It can be presented in two forms: pale sulfonated shale oil (PSSO), and dark sulfonated shale oil (DSSO). DSSO is also sometimes called ichthammol. The last form is a thick reddish brown liquid, possessing a bituminous odor and taste. It is soluble in water and miscible with glycerin, but is nearly insoluble in strong alcohol or concentrated ether. It contains a large percentage of organically combined sulfur. Ichthyol is incompatible with acids, alkali carbonates or hydrates and alkaloidal salts.

Pharmacologically, PSSO and DSSO have anti-inflammatory, bactericidal and fungicidal properties. In otology, a mixture of glycerol and ichthammol® (G & I) has been used for generations for the topical treatment of ear infections. It is efficient against Gram-positive organisms. The anti-inflammatory action is explained by its influence on the formation, secretion and effect of inflammation mediators. DSSO is well tolerated and no indications of teratogenic, mutagenic or carcinogenic effects have been noted.

The European Medicines Agency recently published a Summary Report on ICHTHYOL®-substances (synonym: bituminosulfonates) in course of the European Maximum Residue Limits (MRL) procedure (see report from June 2005) in veterinary medicine. The committee for Medicinal Products for Veterinary Use (CVMP) decided that because of good tolerance and safety there is no need to establish an MRL for ICHTHYOL®-substances. As a result, ICHTHYOL®-substances can be applied topically in all mammalian food producing species without restriction.