Aanika Arjumand | April 5th, 2025
When navigating a world where scientific breakthroughs are constantly reshaping our lives, we tend to place blind trust in medications without doing research of our own on their true impact. While many pharmaceutical drugs and treatments have passed multiple regulatory checks and present minimal risks, there are some that still carry hidden dangers that demand our attention.
Benzalkonium chloride (BAK) is a commonly used preservative in glaucoma medications, chosen for its low cost, easy accessibility, and effectiveness in preventing bacterial contamination. While it is a crucial component in ensuring the sterility of medications, emerging research has highlighted its detrimental adverse effects on the ocular surface. For glaucoma patients, the long-term use of BAK can cause significant damage to the eye, contributing to discomfort, dry eye, and even corneal toxicity. These negative side effects not only affect patients’ quality of life but also serve as a financial burden for managing the disease. The implications of BAK can be further attributed to a barrier in treatment adherence, drawing on insights from a study conducted at Vanderbilt University Medical Center.
The role of BAK in glaucoma treatment
Glaucoma is a leading cause of blindness, affecting 80 million people worldwide. The primary objective of glaucoma treatment is to lower intraocular pressure (IOP) to prevent damage to the optic nerve. Topical medications, including prostaglandins, analogs, beta-blockers, and alpha agonists, are commonly prescribed to control IOP. However, many of these medications are often prescribed as eye drops containing BAK as a preservative, a choice made by pharmaceutical companies to maintain the stability of the eye drop solutions and prevent microbial contamination. As a quaternary ammonium compound, BAK is highly effective at preventing microbial growth, a crucial concern for ophthalmic medications frequently exposed to environmental contamination. The preservative also helps extend the shelf life of the medication, making it a cost-effective choice for pharmaceutical manufacturers.
Ocular damage caused by BAK
Despite its commercial benefits in preserving medication, there is substantial evidence concerning its potential toxicity. The primary concern with BAK is its detrimental impact on the ocular surface. BAK has been shown to disrupt the lipid layer of the tear film, increasing tear evaporation and causing symptoms of dry eye. The resulting symptoms include irritation and inflammation, leading to discomfort, redness, and sensitivity to light. Prolonged exposure to BAK can cause damage to the corneal epithelial cells, loss of conjunctival goblet cells, and delayed corneal wound healing. Moreover, BAK-induced toxicity has been linked to the development of ocular surface disease (OSD), a condition where the surface of the eye is damaged and inflamed. OSD can heighten the difficulty of managing glaucoma by worsening symptoms such as dryness, pain, and blurred vision, ultimately reducing a patient’s quality of life. This potential presence of OSD can create a dangerous cycle for glaucoma patients: the long-term glaucoma treatment further increases their exposure to BAK, which in turn worsens ocular surface disease and leads to a multitude of complications.
Financial strains of BAK-induced ocular surface disease
Besides the usual expenses of medications, doctor visits, and potential surgeries adding up over time, the presence of BAK can amplify these costs even further. Eventually, ocular surface disease caused by BAK will require additional treatments such as lubricating drops, anti-inflammatory medications, and even surgical procedures if the condition becomes severe. Since the cost of these treatments can quickly escalate, it places an additional strain on patients, many of whom are already struggling to manage chronic disease expenses. Patients who suffer from the adverse effects of BAK or eventually ocular surface disease may also experience a reduction in work productivity due to the discomfort and extraneous financial stress. As a result, the use of BAK in glaucoma eye drops may not only worsen patients’ physical health but also their mental health due to the financial burdens.
Medication adherence and the role of BAK
A study conducted in 2022 at Vanderbilt University Medical Center shed light on the barriers to medication adherence in glaucoma patients, many of whom are most likely prescribed BAK-containing eye drops. The study discovered that side effects of glaucoma eye drops, such as eye discomfort, pain, and irritation, significantly impacted patients’ adherence to their medication regime. Nearly 35% of patients reported that their eye drops cause pain or discomfort, and 16.4% of patients admitted to suffering from side effects that interfered with their treatment. These factors contribute to poor medication adherence, which can worsen glaucoma symptoms and lead to further complications. The side effects of BAK-containing eye drops create an unfortunate barrier to adherence, as patients may avoid using their eye drops to avoid discomfort, compromising the effectiveness of the treatment.
Alternative solutions and future implications
As researchers are addressing the growing concerns about the toxic effects of BAK, they are also exploring alternative preservatives and preservative-free glaucoma eye drops. Polyquaternium-1 (Polyquad), oxidizing preservatives such as stabilized oxychloro complex (SOC, trade name Purite) and sodium perborate (GenAqua), and the ionic buffered preservative SofZia are a few classes of preservatives being developed to combat the ocular surface damage caused by BAK. Additionally, preservative-free eye drop formulations are being manufactured and made widely available. However, they are often single-use vials, which are not sustainable and can be hard to keep track of. As research continues to uncover the dangers of BAK, it is vital for clinicians and pharmaceutical manufacturers to consider safer preservative or eye drop alternatives that eliminate detrimental adverse side effects and improve patient care. There must also be an emphasis on increased transparency between the patients and their healthcare providers, so patients are fully aware of how their medication will affect their body. By focusing on preservative-free formulas and patient education, we can help mitigate the harmful effects of BAK and improve the quality of life for glaucoma patients.
References
Gatwood, J et al. (2022). Facilitators and Barriers to Glaucoma Medication Adherence. Journal of Glaucoma, 31(1). doi: 10.1097/IJG.0000000000001965
Goldstein, M et al. (2021) Ocular benzalkonium chloride exposure: problems and solutions. The Scientific Journal of The Royal College of Ophthalmologists. 36(2), 361-368. doi: 10.1038/s41433-021-01668-
Nijm, L et al. (2023). Glaucoma and Dry Eye Disease: Opportunity to Assess and Treat. Dovepress Clinical Ophthalmology. 3063-3076. doi: 10.2147/OPTH.S420932.
Steven, D et al. (2018) Preservatives in glaucoma medication. British Journal of Ophthalmology. 102(11), 1497-1503. doi: 10.1136/bjophthalmol-2017-311544.
Zhou, X et al. (2022). A Narrative Review of Ocular Surface Disease Related to Anti-Glaucomatous Medications. Ophthalmology and Therapy. 11(5), 1681-1704. doi: 10.1007/s40123-022-00557-0.
