Products
Benzalkonium chloride is commercially available as an active pharmaceutical ingredient in the form of lozenges, as a gargling solution, as a gel and as a disinfectant, among others. As a preservative, it is commonly added in pharmaceuticals to eye drops, nasal sprays, nose drops and inhalation solutions for asthma and COPD treatment. It is also found in personal care products.
Structure and properties
Benzalkonium chloride is a surface-active quaternary ammonium compound. It is a mixture of alkylbenzyldimethylammonium chlorides whose alkyl moiety consists of C8– to C18 chains. Benzalkonium chloride is present as a white to yellowish white powder or as gelatinous yellowish white pieces. The substance is hygroscopic, soapy to the touch, and very soluble in water. An aqueous solution forms a strong foam when shaken.
Effects
Benzalkonium chloride is antibacterial and antiviral against some enveloped viruses (e.g., herpes virus, hepatitis B virus, influenza virus). It is less effective against gram-negative bacteria, fungi, and spores. Some sources also attribute antifungal properties to it. The effects are due to disruption of cell membrane permeability and protein and enzyme function.
Indications for use
Therapeutic indications:
- Topical disinfection, for example, for inflammation of the mouth and throat, for skin disinfection.
- As a spermicide for contraception, see under benzalkonium chloride tampons.
Pharmaceutical excipient:
- As a preservative for medicinal products.
Contraindications
Benzalkonium chloride is contraindicated in case of hypersensitivity. Full precautions can be found in the drug label.
Interactions
Benzalkonium chloride is inactivated by proteins, serum, and pus. Soaps, porous materials such as rubber, cotton, and cork, and plastics and lipids may reduce effectiveness. Benzalkonium chloride may attach to soft contact lenses. Therefore, lenses should not be worn when administering eye drops containing the preservative. They should be removed and not reinserted until 15 minutes after application.
Adverse effects
Benzalkonium chloride is known for its skin-irritating properties. Whether it also causes allergic reactions is controversial in the literature (Basketter et al 2004). On the eye, benzalkonium chloride can lead to corneal disorders (keratitis punctata, toxic ulcerative keratitis). Other side effects such as dry eyes and histological changes have been associated with benzalkonium chloride (e.g., Rasmussen et al., 2014). Because of the adverse effects, eye drops without preservatives are now marketed. These include the monodoses and specially designed dropper bottles whose contents are not contaminated during application (e.g., ABAK, COMOD system). Benzalkonium chloride has also been associated with the development or exacerbation of rhinitis medicamentosa, or “dependence” on decongestant nasal sprays. It can affect the nasal mucosa. Benzalkonium chloride is also used as a preservative for inhalation solutions in asthma and COPD therapy, as mentioned earlier. Cases of paradoxical bronchospasm attributed to the preservative have been reported in the literature (George et al., 2017). Single doses without preservative are also available as an alternative. In summary, it seems reasonable to preferentially dispense or use medications without the preservative due to the potential adverse effects.