Gentian violet is variously known as hexamethyl-^-rosani-line chloride, crystal violet, methyl violet, and methyl-rosaniline chloride. It occurs as a green powder or green flakes with a metallic sheen. The compound is soluble in water (1:35) and alcohol (1:10) but insoluble in nonpolar organic solvents. Gentian violet is available in vaginal suppositories for the treatment of yeast infections. It is also used as a 1% to 3% solution for the treatment of ringworm and yeast infections. Gentian violet has also been used orally as an anthelmintic for strongyloidiasis (threadworm) and oxyuriasis.
Basic fuchsin is a mixture of the chlorides of rosaniline and ^-rosaniline. It exists as a green crystalline powder with a metallic appearance. The compound is soluble in water and in alcohol but insoluble in ether. Basic fuchsin is a component of carbol-fuchsin solution (Castellani's paint), which is used topically in the treatment of fungal infections, notably ringworm and athlete's foot.
Methylene blue is 3,7-bis(dimethylamino)-phenazathionium chloride (Urised). The compound occurs as a dark green crystalline powder with a metallic appearance that is soluble in water (1:25) and alcohol (1:65).
Methylene blue has weak antiseptic properties that make it useful for the treatment of cystitis and urethritis. The action of methylene blue is considered to be bacteriostatic. The compound colors the urine and stool blue green.
O MERCURY COMPOUNDS (MERCURIALS)
Mercury and its derivatives have been used in medicine for centuries. Elemental mercury incorporated into ointment bases was used topically for the treatment of localized infections and syphilis. Several inorganic salts of mercury, such as mercuric chloride (HgCl2) and mercurous chloride (calomel, Hg2Cl2) were at one time widely used as antiseptics. Ammoniated mercury [Hg(NH2)Cl] is still occasionally used for skin infections such as impetigo, psoriasis, and ringworm. Mercuric oxide is sometimes used to treat inflammation resulting from infection of the eye. Although the potential interaction of mercuric ion with the tissues is greatly reduced by the low water solubility of these agents, they can be irritating and can cause hypersensitivity reactions; therefore, their use is not recommended.
The comparatively few organomercurials still in use are employed as antiseptics, preservatives, or diuretics. Organomercurials can be grouped into two general classes: (a) compounds with at least one carbon-mercury bond that does not ionize readily and (b) compounds with mercury bonded to heteroatoms (e.g., oxygen, nitrogen, sulfur) that ionize partially or completely. In addition to its effect on ionization, the organic moiety may increase the lipid solubility of an organomercurial compound, thereby facilitating its penetration into microorganisms and host tissues.
The antibacterial action of mercury compounds is believed to result from their reaction with sulfhydryl (-SH) groups in enzymes and other proteins to form covalent compounds of the type R-S-Hg-R'. This action is reversible by treatment with thiol-containing compounds such as cysteine and dimercaprol (BAL); hence, organomercurials, reacting reversibly, are largely bacteriostatic. The antibacterial activity of organomercurial antiseptics is greatly reduced in serum because of the presence of proteins that inactivate mercury compounds. Organomercurial antiseptics are not very effective against spores.
The disadvantages of mercurials for antiseptic and disinfectant uses far outweigh any possible advantages that they might have. Hence, other more effective and less potentially toxic agents are preferable.
3-(Hydroxymercuri)-4-nitro-tf-cresol inner salt (Metaphen) occurs as a yellow powder that is practically insoluble in
water and is sparingly soluble in alcohol and most organic solvents. The sodium salt probably has the "inner salt" structure in which the inner shell electrons of mercury are occupied.15 The bonding to mercury in this salt should be collinear, thus the following structure is somewhat improbable. Nevertheless, this structure is shown in the USP and the Merck Index.
Nitromersol is nonirritating to mucous membranes and is nonstaining. Therefore, at one time, it was a very popular antiseptic for skin and ocular infections. Nitromersol has largely been replaced by superior agents.
[(o-Carboxyphenyl)-thio]ethylmercury sodium salt (Merthiolate) is a cream-colored, water-soluble powder. It is nonstaining and nonirritating to tissues. Thimerosal is a weakly bacteriostatic antiseptic that is applied topically in ointments or aqueous solutions.
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