Can discontinuing tobramycin (an aminoglycoside antibiotic) eye drops cause acute angle glaucoma?

No Evidence Supporting Acute Angle-Closure Glaucoma from Discontinuing Tobramycin Eye Drops

There is no evidence in the medical literature supporting that discontinuation of tobramycin eye drops can cause acute angle-closure glaucoma.

Understanding Acute Angle-Closure Glaucoma

Acute angle-closure glaucoma (AACG) is an ophthalmic emergency characterized by:

• Severe eye pain
• Blurred vision
• Halos around lights
• Headache
• Nausea/vomiting
• Eye redness
• Mid-dilated pupil 1

This condition occurs when the drainage angle between the iris and cornea becomes blocked, causing rapid increase in intraocular pressure (IOP) that can lead to permanent vision loss if not treated promptly.

Risk Factors for Acute Angle-Closure Glaucoma

The American Academy of Ophthalmology identifies several risk factors for AACG:

Anatomical Risk Factors:

• Hyperopia
• Shallow anterior chamber depth
• Short axial length
• Thick crystalline lens
• Steep corneal curvature 1, 2

Demographic Risk Factors:

• Asian descent (particularly Chinese)
• Older age (>50 years)
• Female gender
• Family history of angle closure 1

Medications Associated with Acute Angle-Closure Glaucoma

Several medications can precipitate AACG through different mechanisms:

1. Pupillary block mechanism (treatable by peripheral iridotomy):

   • Adrenergic agents (local or systemic)
   • Anticholinergic medications (tropicamide, atropine)
   • Tricyclic and tetracyclic antidepressants
   • Cholinergic agents like pilocarpine 3

2. Ciliary body edema mechanism (not responsive to iridotomy):

   • Sulfa-based drugs (acetazolamide, hydrochlorothiazide, cotrimoxazole)
   • Topiramate 3, 4

3. Other documented cases:

   • Homeopathic eyedrops containing Atropa belladonna 5
   • Discontinuation of escitalopram (antidepressant) 6

Tobramycin and Angle-Closure Glaucoma

Tobramycin is an aminoglycoside antibiotic commonly used in ophthalmic preparations. Based on the available evidence:

1. None of the guidelines from the American Academy of Ophthalmology mention tobramycin or aminoglycoside antibiotics as potential causes of AACG 2, 1.

2. Comprehensive reviews of drug-induced AACG do not list tobramycin or aminoglycosides as causative agents 7, 3.

3. The pharmacological mechanism of tobramycin (bacterial protein synthesis inhibition) does not suggest a plausible mechanism for causing angle closure upon discontinuation.

Clinical Implications

When evaluating a patient with symptoms suggestive of AACG:

1. Focus on known risk factors and medications associated with AACG
2. Consider anatomical predisposition (narrow angles)
3. Review all medications, particularly those with anticholinergic, adrenergic, or sulfa-based properties
4. Remember that most attacks occur in individuals unaware they have narrow iridocorneal angles 3

Conclusion

While medication-induced AACG is well-documented for several drug classes, there is no evidence supporting that discontinuation of tobramycin eye drops can cause acute angle-closure glaucoma. Clinicians should focus on established risk factors and known causative medications when evaluating patients with symptoms of AACG.