Compendium of the most significant studies with reference to properties, intake, effects.

Seino S, Takada Y, Saika S. Effects of Benzalkonium Chloride in Ophthalmic Eyedrop Medications on Corneal Epithelium. Yakugaku Zasshi. 2021;141(1):35-39. doi: 10.1248/yakushi.20-00177-1. 

Abstract. Eyedrops often contain additives other than active pharmaceutical ingredients, such as preservatives. The most frequently used preservative is benzalkonium chloride (BAC). When the ocular surface is exposed to eyedrops, the active pharmaceutical ingredients and additives can cause corneal epithelial disorder. Particularly in clinical settings, there is great interest in corneal epithelial disorders resulting from the use of glaucoma eyedrops, which is inevitable when instilled for a long period of time after the onset of disease. At the authors' institute, glaucoma is treated with consideration of reducing corneal epithelial disorder while ensuring the effect of lowering intraocular pressure by the appropriate choice of eyedrops. In this review, we show the examples of the retrospective studies. Sodium hyaluronate eyedrops are prescribed for corneal epithelial disorders such as superficial punctate keratitis associated with dry eye. Prescribable concentrations of sodium hyaluronate in Japan are 0.1% or 0.3%, and the 0.3% formulation does not contain BAC. The authors' study showed that 0.3% sodium hyaluronate pretreatment reduced the cytotoxicity of BAC in cultured corneal epithelial cells, whereas an in vivo study in mice showed that a 0.3% sodium hyaluronate instillation was suggested and that the drug may enhance the cytotoxicity of separately administered BAC. It is suggested that sodium hyaluronate prolonged the retention of BAC on the ocular surface. However, there have been no reports of this problem in the clinical setting. It is important for ophthalmologists to understand the properties of additives other than the active pharmaceutical ingredients in eyedrops.

Goldstein MH, Silva FQ, Blender N, Tran T, Vantipalli S. Ocular benzalkonium chloride exposure: problems and solutions. Eye (Lond). 2022 Feb;36(2):361-368. doi: 10.1038/s41433-021-01668-x. 

Abstract. Preservatives in multidose formulations of topical ophthalmic medications are crucial for maintaining sterility but can be toxic to the ocular surface. Benzalkonium chloride (BAK)-used in approximately 70% of ophthalmic formulations-is well known to cause cytotoxic damage to conjunctival and corneal epithelial cells, resulting in signs and symptoms of ocular surface disease (OSD) including ocular surface staining, increased tear break-up time, and higher OSD symptom scores. These adverse effects are more problematic with chronic exposure, as in lifetime therapy for glaucoma, but can also manifest after exposure as brief as seven days. Multiple strategies are available to minimize or eliminate BAK exposure, among them alternative preservatives, preservative-free formulations including sustained release drug delivery platforms, and non-pharmacological therapies for common eye diseases and conditions. In this paper, we review the cytotoxic and clinical effects of BAK on the ocular surface and discuss existing and emerging options for ocular disease management that can minimize or eliminate BAK exposure. © 2021. The Author(s).

Kabashima K, Murakami A, Ebihara N. Effects of Benzalkonium Chloride and Preservative-Free Composition on the Corneal Epithelium Cells. J Ocul Pharmacol Ther. 2020 Nov;36(9):672-678. doi: 10.1089/jop.2019.0165.

Abstract. Purpose: Benzalkonium Chloride (BAK) is reported to have the potential to damage the cornea. We developed a composition with broad-spectrum antimicrobial activity without preservatives by combining trometamol, boric acid, and ethylenediaminetetraacetic acid (TBE). This study aimed at evaluating the corneal damage caused by TBE and comparing it with that caused by BAK. Methods: SV40-immortalized human corneal epithelial cell line (HCE-T) was treated with BAK or TBE, and the cell viability was measured. The exposure time that caused 50% cell death (CDT50) was calculated. Transepithelial electrical resistance (TEER) was measured before and after treatment with BAK or TBE. Occludin was detected with immunostaining and Western blotting after treatment with BAK or TBE. The effect of BAK or TBE on membrane-associated mucins was evaluated with rose bengal (RB) staining. Results: In the BAK group, cell viability decreased in a dose-dependent manner. The viability of the TBE group was significantly greater than that of the BAK group. The CDT50 of the TBE group is greater than that of the BAK groups. In the BAK groups, the recovery of TEER was delayed in a dose-dependent manner, whereas in the TBE group, the recovery occurred earlier. Localization of occludin was disrupted, and the amount of occludin was significantly reduced among the cells exposed to BAK. The area stained with RB in the BAK groups increased, whereas that in the TBE group did not increase. Conclusion: These results suggest that the application of TBE would be useful for developing preservative-free ophthalmic preparations that offer both sufficient safety and antimicrobial activity.

Johnson NF. Pulmonary Toxicity of Benzalkonium Chloride. J Aerosol Med Pulm Drug Deliv. 2018 Feb;31(1):1-17. doi: 10.1089/jamp.2017.1390.

Abstract. The available toxicity data of benzalkonium chloride (BKC) clearly shows that it is toxic; however, the weight of evidence favors the view that at doses encountered in nasally and orally inhaled pharmaceutical preparations it is well tolerated. The adverse toxicological data predominantly come from in vitro and animal studies in which doses and exposure periods employed were excessive in relation to the clinical doses and their posology and, therefore, not directly applicable to the clinic. The conflict between the in vitro and animal data and the clinical experience can be reconciled by understanding some of the physicochemical properties of BKC, the nasal and respiratory tract microenvironments, the doses used, and the posology.

Rasmussen CA, Kaufman PL, Kiland JA. Benzalkonium chloride and glaucoma. J Ocul Pharmacol Ther. 2014 Mar-Apr;30(2-3):163-9. doi: 10.1089/jop.2013.0174.

Abstract. Glaucoma patients routinely take multiple medications, with multiple daily doses, for years or even decades. Benzalkonium chloride (BAK) is the most common preservative in glaucoma medications. BAK has been detected in the trabecular meshwork (TM), corneal endothelium, lens, and retina after topical drop installation and may accumulate in those tissues. There is evidence that BAK causes corneal and conjunctival toxicity, including cell loss, disruption of tight junctions, apoptosis and preapoptosis, cytoskeleton changes, and immunoinflammatory reactions. These same effects have been reported in cultured human TM cells exposed to concentrations of BAK found in common glaucoma drugs and in the TM of primary open-angle glaucoma donor eyes. It is possible that a relationship exists between chronic exposure to BAK and glaucoma. The hypothesis that BAK causes/worsens glaucoma is being tested experimentally in an animal model that closely reflects human physiology.

Romanowski EG, Yates KA, Shanks RMQ, Kowalski RP. Benzalkonium Chloride Demonstrates Concentration-Dependent Antiviral Activity Against Adenovirus In Vitro. J Ocul Pharmacol Ther. 2019 Jun;35(5):311-314. doi: 10.1089/jop.2018.0145.

Abstract. Purpose: Adenoviral conjunctivitis is the most common cause of conjunctivitis worldwide with no approved antiviral treatment. Benzalkonium chloride (BAK) is a common preservative in ophthalmic medications and is the active ingredient in some skin disinfectants and hand sanitizers. BAK is known to be effective in killing bacteria and enveloped viruses; however, its activity against ocular types of nonenveloped adenoviruses (Ads) is unknown. The goal was to determine whether BAK is an effective antiviral agent against common human ocular types of adenovirus in vitro. Methods: The direct inactivating activity of BAK was determined by incubating several human adenovirus types with BAK concentrations of 0.001%, 0.003%, 0.005%, 0.01%, 0.1%, and 0% for 1 h at 33°C. Resulting adenovirus titers were determined after treatment. Decreases in titers of ≥3 Log10 were considered virucidal, while decreases in titers of <1 Log10 were considered ineffective. Results: BAK 0.1% was virucidal for Ad3, Ad5, Ad7a, Ad19/64, and Ad37, while it reduced titers >1 Log10, but <3 Log10 for Ad4 and Ad8. Decreases in titers >1 Log10 were demonstrated for BAK 0.003%, 0.005%, and 0.01% for Ad5 only. Decreases in titers for the other adenovirus types for those concentrations were ≤0.53 Log10. 0.001% BAK produced minimal decreases in titers for all types. Conclusions: BAK, at 0.01% or less was not consistently effective as an antiviral against adenovirus, but higher concentrations, such as 0.1%, should be further investigated as a possible topical treatment for adenoviral ocular infections, providing ocular toxicity is not an issue.

Choi SM, Roh TH, Lim DS, Kacew S, Kim HS, Lee BM. Risk assessment of benzalkonium chloride in cosmetic products. J Toxicol Environ Health B Crit Rev. 2018;21(1):8-23. doi: 10.1080/10937404.2017.1408552.

Abstract. A risk assessment of benzalkonium chloride (BAC) was conducted based upon its toxicological profile and exposure evaluation. Since 1935, BAC has been used in a wide variety of products such as disinfectants, preservatives, and sanitizers. It is well-established that BAC is not genotoxic nor does it display tumorigenic potential, but safety concerns have been raised in local usage such as for ocular and intranasal applications. The Foundation of Korea Cosmetic Industry Institute (KCII) reported that in a hair conditioner manufactured as a cosmetic or personal product in South Korea, BAC was present at concentrations of 0.5-2%. The systemic exposure dosage (SED) was determined using the above in-use concentrations and a risk assessment analysis was conducted. The Margin of Safety (MOS) values for hair conditioners were calculated to be between 621 and 2,483. The risk of certain personal and cosmetic products was also assessed based upon assumptions that BAC was present at the maximal level of regulation in South Korea and that the maximal amount was used. The MOS values for the body lotion were all above 100, regardless of the application site. Collectively, data indicate that there are no safety concerns regarding use of products that contain BAC under the current concentration restrictions, even when utilized at maximal permitted levels. However, a chronic dermal toxicity study on BAC and comprehensive dermal absorption evaluation needs to be conducted to provide a more accurate prediction of the potential health risks to humans.

Wu JH, Wang TH, Huang JY, Su CC. Ocular Surface Disease in Glaucoma Patients Randomized to Benzalkonium Chloride-Containing Latanoprost and Preservative-Free Bimatoprost. J Ocul Pharmacol Ther. 2021 Oct 4. doi: 10.1089/jop.2021.0071.

Abstract. Purpose: To investigate the influence of benzalkonium chloride (BAK) on ocular surface disease (OSD) in glaucoma patients receiving ocular-hypotensive agent. Methods: Patients were randomized to receive BAK-containing latanoprost (Xalatan) or preservative-free bimatoprost (Lumigan PF). Intraocular pressure (IOP), basal Schirmer's test, noninvasive keratograph tear-breakup time (TBUT), conjunctival redness score (R score), OSD index (OSDI), and corneal Oxford staining were recorded and compared between the 2 groups at 1-month and 4-month visits. The influence of BAK was analyzed by a generalized estimating equation model. Results: We enrolled 74 and 76 eyes treated with latanoprost and bimatoprost, respectively. The IOP decreased in both groups, although greater reduction was observed for latanoprost (13.95 vs. 15.42 mmHg, P = 0.0264). There was a significantly negative association between tear flow and latanoprost use (β = -0.763, P = 0.0243). The first and average TBUT did not show intergroup differences, but the area with unstable tear film increased with latanoprost use and showed marginal significance at 4-month visit (9.33% vs. 5.94% P = 0.055). In both groups, OSDI decreased, whereas Oxford stain increased over time, and R scores showed improvement after transient increase in the first month. The bimatoprost group had significantly worse conjunctival hyperemia, whereas a negative association with conjunctival hyperemia was revealed for latanoprost use (R score-bulbar nasal: β = -0.045, P = 0.0423). Conclusions: BAK-containing latanoprost was associated with decreased tear secretion and may be associated with tear-film instability, whereas bimatoprost was associated with worse conjunctival hyperemia. Ocular surface side effects should be considered when prescribing BAK-containing medication to glaucoma patients.

Yamashiro C, Tokuda K, Kobayashi Y, Higashijima F, Yoshimoto T, Ota M, Ogata T, Ashimori A, Kobayashi M, Hatano M, Uchi SH, Wakuta M, Teranishi S, Kimura K. Benzalkonium chloride-induced myofibroblastic transdifferentiation of Tenon's capsule fibroblasts is inhibited by coculture with corneal epithelial cells or by interleukin-10. Sci Rep. 2021 Aug 9;11(1):16096. doi: 10.1038/s41598-021-94852-8.

Abstract. Benzalkonium chloride (BAC) is used as a preservative in eyedrops but induces subconjunctival fibrosis that can result in failure of glaucoma surgery. Tenon's capsule fibroblasts in subconjunctival tissue interact with the corneal epithelium through tear fluid. With the use of a coculture system, we have now investigated the effect of human corneal epithelial (HCE) cells on myofibroblastic transdifferentiation of human Tenon fibroblasts (HTFs) induced by BAC (5 × 10-6%). Immunofluorescence and immunoblot analyses revealed that the BAC-induced expression of α smooth muscle actin (αSMA) in HTFs was suppressed by coculture of these cells with HCE cells (p < 0.01). The concentration of interleukin-10 (IL-10) in culture supernatants of BAC-treated HTFs was increased by coculture with HCE cells (17.26-fold, vs. coculure, p < 0.001). Immunofluorescence and immunoblot analyses also showed that exogenous IL-10 (300 pg/ml) suppressed the BAC-induced expression of αSMA by 43.65% (p < 0.05) as well as the nuclear translocation of myocardin-related transcription factor-A (MRTF-A) by 39.32% (p < 0.01) in HTFs cultured alone. Our findings suggest that corneal epithelial cells may protect against subconjunctival fibrosis by maintaining IL-10 levels and preventing the MRTF-A-dependent transdifferentiation of HTFs into myofibroblasts.