Benzalkonium Chloride

Benzalkonium Chloride

Benzalkonium Chloride

Benzalkonium chloride occurs as a white or yellowish-white amorphous powder, a thick gel, or gelatinous flakes. It is hygroscopic, soapy to the touch, and has a mild aromatic odor and very bitter taste.

Nonproprietary Names

  • BP: Benzalkonium Chloride
  • JP: Benzalkonium Chloride
  • PhEur: Benzalkonium Chloride
  • USP-NF: Benzalkonium Chloride

Alkylbenzyldimethylammonium chloride; alkyl dimethyl benzyl ammonium chloride; benzalkonii chloridum; BKC; Hyamine 3500; Pentonium; Zephiran.

Chemical Name and CAS Registry Number Alkyldimethyl(phenylmethyl)ammonium chloride [8001-54-5]

Empirical Formula and Molecular Weight

The USP32–NF27 describes benzalkonium chloride as a mixture of alkylbenzyldimethylammonium chlorides of the general formula [C6H5CH2N(CH3)2R]Cl, where R represents a mixture of alkyls, including all or some of the group beginning with n-C8H17 and extending through higher homologs, with n-C12H25, n-C14H29, and n-C16H33 comprising the major portion. The average molecular weight of benzalkonium chloride is 360.

Functional Category

Antimicrobial preservative; antiseptic; disinfectant; solubilizing agent; wetting agent.

Applications in Pharmaceutical Formulation or Technology

Benzalkonium chloride is a quaternary ammonium compound used in pharmaceutical formulations as an antimicrobial preservative in applications similar to other cationic surfactants, such as cetrimide. In ophthalmic preparations, benzalkonium chloride is one of the most widely used preservatives, at a concentration of 0.01–0.02% w/v. Often it is used in combination with other preservatives or excipients, particularly 0.1% w/v disodium edetate, to enhance its antimicrobial activity against strains of Pseudomonas.

In nasal, and otic formulations a concentration of 0.002–0.02% w/v is used, sometimes in combination with 0.002–0.005% w/v thimerosal. Benzalkonium chloride 0.01% w/v is also employed as a preservative in small-volume parenteral products. Benzalkonium chloride was also shown to enhance the topical penetration of lorazepam. Benzalkonium chloride is additionally used as a preservative in cosmetics.

Method of Manufacture

Benzalkonium chloride is formed by the reaction of a solution of Nalkyl- N-methylbenzamine with methyl chloride in an organic solvent suitable for precipitating the quaternary compound as it is formed.

Related Substances

Benzethonium chloride; cetrimide.

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