Phenylmercuric Nitrate

Synonyms: Basic phenylmercury nitrate; mercuriphenyl nitrate; merphenyl nitrate; nitratophenylmercury; phenylhydrargyri nitras; phenylmercury nitrate; Phe-Mer-Nite; PMN.

Description: Phenylmercuric nitrate PhEur 6.0, and USP32–NF27, is an equimolecular compound of phenylmercuric hydroxide and phenylmercuric nitrate; it occurs as a white, crystalline powder with a slight aromatic odor.

Chemical Name: Hydroxyphenylmercury mixture with (nitrato-O)phenylmercury:

Antimicrobial preservative.

• Phenylmercuric salts are used as antimicrobial preservatives mainly in ophthalmic preparations, but are also used in cosmetics , parenteral, and topical pharmaceutical formulations

• Phenylmercuric salts are active over a wide pH range against bacteria and fungi and are usually used in neutral to alkaline solutions, although they have also been used effectively at slightly acid pH.

• In acidic formulations, phenylmercuric nitrate may be preferred to phenylmercuric acetate or phenylmercuric borate as it does not precipitate.

• Phenylmercuric nitrate is also an effective spermicide, although its use in vaginal contraceptives is no longer recommended.

• A number of adverse reactions to phenylmercuric salts have been reported, and concern at the toxicity of mercury compounds may preclude the use of phenylmercuric salts under certain circumstances

The antimicrobial activity of phenylmercuric salts may be reduced in the presence of anionic emulsifying agents and suspending agents, tragacanth, starch, talc, sodium metabisulfite, sodium thiosulfate, disodium edetate and silicates (bentonite, aluminum magnesium silicate, magnesium trisilicate, and kaolin). Phenylmercuric salts are incompatible with halides, particularly bromides and iodides, as they form less-soluble halogen compounds. At concentrations of 0.002% w/v precipitation may not occur in the presence of chlorides. Phenylmercuric salts are also incompatible with aluminum and other metals, ammonia and ammonium salts, amino acids, and with some sulfur compounds, e.g. in rubber

Phenylmercuric nitrate and other phenylmercuric salts have been widely used as antimicrobial preservatives in parenteral and topical pharmaceutical formulations. However, concern over the use of phenylmercuric salts in pharmaceuticals has increased as a result of greater awareness of the toxicity of mercury and other mercury compounds. This concern must, however, be balanced by the effectiveness of these materials as antimicrobial preservatives and the low concentrations in which they are employed.

Observe normal precautions appropriate to the circumstances and quantity of material handled. Phenylmercuric nitrate may be irritant to the skin, eyes, and mucous membranes. Eye protection, gloves, and a respirator are recommended.

Phenylmercuric acetate; phenylmercuric borate; thimerosal.