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Benzalkonium chloride
General information
Quaternary ammonium compounds are surface-active agents. Some of them precipitate or denature proteins and destroy microorganisms. The most important disinfectants in this group are cationic surface-active agents, such as benzalkonium chloride, benzethonium chloride and methylbenzethonium chloride, and cetylpyridinium chloride; the problems that they cause are similar.
Benzalkonium chloride is composed of a mixture of alkyldimethylbenzylammonium chlorides. The hydrophobic alkyl residues are paraffinic chains with 8–18 carbon atoms. Benzalkonium chloride is used as a preservative in suspensions and solutions for nasal sprays and in eye-drops. Depending on the concentration of the solution, local irritant effects can occur. In nasal sprays it can exacerbate rhinitis [ ] and in eye-drops it can cause irritation or keratitis [ ].
A total of 125 ophthalmologists in private practice located throughout France examined 919 glaucomatous patients treated with eye-drops which either did or did not contain a preservative; the proportion of patients who experienced discomfort or pain during instillation was 58% for eye-drops containing a preservative and 30% for eye-drops with no preservative [ ]. Moreover, the proportion of patients presenting at least one symptom of eye irritation (sensation of itching or burning, sensation of a foreign body in the eye, and flow of tears) was greater with preservative-containing eye-drops (53 versus 34%). The experience of discomfort during instillation was more often associated with problems later on. The patient’s complaints were correlated with objective signs of conjunctival damage (conjunctival redness, conjunctival follicles), or corneal damage (superficial punctate keratitis). A higher proportion of patients treated with eye-drops containing a preservative had at least one conjunctival sign (52 versus 35%) or superficial punctate keratitis (12 versus 4%). In 164 patients whose treatment was changed from eye-drops containing a preservative to eye-drops with no preservative and who were examined a second time (mean interval between visits 3.3 months) the frequency of all symptoms and objective signs fell by a factor of 3–4.
Drug studies
Comparative studies
Benzalkonium chloride is widely used as a preservative in eye-drops, in higher concentrations it is used as an antiseptic and disinfectant. In a randomized crossover study two concentrations of benzalkonium chloride, 0.1% and 0.4%, used as a sanitary wipe were compared with a 62% ethyl alcohol emollient gel for safety and acceptability in male genital antisepsis [ ]. Of the 39 participants one reported dry skin with 0.1% benzalkonium and a genital ulcer was reported in one patient assigned to 0.4% benzalkonium. No adverse effects were observed during use of the ethanol gel, which was preferred by most men.
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