Do dilating eye drops contain Benzalkonium Chloride (BAK)?

Presence of Benzalkonium Chloride (BAK) in Dilating Eye Drops

Yes, many dilating eye drops contain benzalkonium chloride (BAK) as a preservative, as confirmed by FDA drug labels for common mydriatic agents like phenylephrine and tropicamide. 1, 2

Evidence of BAK in Common Dilating Drops

• Phenylephrine 10%: Contains 0.01% benzalkonium chloride as a preservative according to the FDA label 1
• Tropicamide 1%: Contains 0.01% benzalkonium chloride as a preservative according to the FDA label 2

Clinical Significance of BAK in Ophthalmic Preparations

BAK is the most commonly used preservative in ophthalmic medications due to its broad antimicrobial activity. However, it has well-documented toxic effects on the ocular surface, including:

• Tear film instability
• Loss of goblet cells
• Conjunctival inflammation and fibrosis
• Disruption of corneal epithelial barrier
• Epithelial apoptosis
• Subconjunctival fibrosis 3

Patient Risk Factors for BAK Toxicity

The risk of BAK-related adverse effects increases with:

1. Frequency of use: Higher exposure with multiple daily applications
2. Duration of treatment: Long-term use increases cumulative toxicity
3. Pre-existing ocular surface disease: Patients with dry eye are more vulnerable
4. Multiple medications: Combined preservative load from different eye drops 3, 4

Clinical Recommendations

High-Risk Patients Who Should Use Preservative-Free Options:

• Patients with pre-existing ocular surface disease
• Those requiring frequent eye drop administration
• Patients with proven allergy to preservatives
• Contact lens wearers 5
• Patients with severe dry eye syndrome 6

Specific Guidance for Dilating Drops:

• For routine dilated eye examinations in healthy patients, standard BAK-preserved dilating drops are generally well-tolerated for single-use applications
• For patients with ocular surface disease, preservative-free formulations are recommended 6
• When dilating drops are needed for patients with Stevens-Johnson syndrome/toxic epidermal necrolysis, non-preserved formulations (e.g., non-preserved dexamethasone 0.1%) should be used 6

Alternatives to BAK-Preserved Dilating Drops

When preservative-free options are indicated, consider:

• Preservative-free unit-dose formulations
• Drops with alternative, less toxic preservatives such as:
  • Polyquaternium-1 (Polyquad)
  • Sodium perborate
  • Oxychloro-complex (Purite®)
  • SofZia 5, 7

Conclusion

While BAK is present in most standard dilating eye drops, its clinical significance depends on patient factors and frequency of use. For routine dilated examinations in patients without ocular surface disease, the benefits of BAK-preserved dilating drops typically outweigh the risks. However, preservative-free alternatives should be considered for high-risk patients to minimize ocular surface damage and discomfort.