PHENYLMERCURY NITRATE

Chemical Properties

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 Properties

white crystalline powder

Uses

Pharmaceutic aid (antimicrobial agent).

Production Methods

Phenylmercuric nitrate is readily formed by heating benzene with mercuric acetate, and treating the resulting acetate with an alkali nitrate.

Definition

ChEBI: Phenylmercuric nitrate is a member of benzenes.

brand name

Phenmerzyl Nitrate (Marion Merrell Dow).

General Description

Lustrous scales decomposing at 187-190°C. Very slightly soluble in water. Used as an antiseptic, germicide, fungicide.

Air & Water Reactions

Very slightly soluble in water.

Reactivity Profile

Strongly reactive with many other groups. Incompatible with acids and bases. Organometallics are good reducing agents and therefore incompatible with oxidizing agents. Often reactive with water to generate toxic or flammable gases. Generally highly toxic. Often react on contact with tissues to give toxic products.

Health Hazard

Highly toxic, may be fatal if inhaled, swallowed or absorbed through skin. Avoid any skin contact. Effects of contact or inhalation may be delayed. Fire may produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may be corrosive and/or toxic and cause pollution.

Fire Hazard

Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive and/or toxic fumes. Containers may explode when heated. Runoff may pollute waterways.

Pharmaceutical Applications

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;

Safety Profile

Poison by intravenous route. FDA over-the-counter drug. When heated to decomposition it emits very toxic fumes of Hg and NOx. See also MERCURY COMPOUNDS and NITRATES.

Safety

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.
Phenylmercuric salts are irritant to the skin at 0.1% w/w concentration in petrolatum.In solution, they may give rise to erythema and blistering 6–12 hours after administration. In a modified repeated insult patch test, a 2% w/v solution was found to produce extreme sensitization of the skin.
Eye drops containing phenylmercuric nitrate as a preservative should not be used continuously for prolonged periods as mercurialentis, a brown pigmentation of the anterior capsule of the lens may occur. Incidence is 6% in patients using eye drops for greater than 6 years; however, the condition is not associated with visual impairment.Cases of atypical band keratopathy have also been attributed to phenylmercuric nitrate preservative in eye drops.
Concern that the absorption of mercury from the vagina may be harmful has led to the recommendation that phenylmercuric nitrate should not be used in intravaginal formulations.
(mouse, IV): 27 mg/kg
(mouse, oral): 50 mg/kg
(rat, SC): 63 mg/kg

storage

All phenylmercuric compound solutions form a black residue of metallic mercury when exposed to light or after prolonged storage. Solutions may be sterilized by autoclaving, although significant amounts of phenylmercuric salts may be lost, hence reducing preservative efficacy, owing to incompatibilities with packaging components or other excipients, e.g. sodium metabisulfite.
Phenylmercuric nitrate should be stored in a well-closed container, protected from light, in a cool, dry place.

Incompatibilities

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 salts are absorbed by rubber stoppers and some types of plastic packaging components; uptake is usually greatest to natural rubbers and polyethylene, and least to polypropylene. Incompatibilities with some types of filter membranes may also result in loss of phenylmercuric salts following sterilization by filtration.

Regulatory Status

Included in the FDA Inactive Ingredients Database (parenteral and ophthalmic preparations). Included in parenteral products and eye drops in the EU. Included in the Canadian List of Acceptable Nonmedicinal Ingredients (ophthalmic, nasal and otic preparations only up to 0.002%; there must be no other suitable alternative preservative).
Prohibited in first aid antiseptic drug products, antimicrobial diaper rash drug products and vaginal contraceptive drug products in the USA. Limited uses permitted in Japan and the EU for cosmetics.