Doxepin is Generally Safe in Open-Angle Glaucoma
Doxepin can be used safely in patients with open-angle glaucoma, as the FDA label explicitly states that "open-angle glaucoma is not a risk factor for angle closure glaucoma" and the concern with doxepin is specifically for angle-closure glaucoma, not open-angle glaucoma. 1
Key Distinction: Open-Angle vs. Angle-Closure Glaucoma
The critical issue is understanding which type of glaucoma poses risk with anticholinergic medications:
Open-angle glaucoma patients are NOT at increased risk from doxepin's pupillary effects, as the FDA label clearly differentiates that "pre-existing glaucoma is almost always open-angle glaucoma because angle closure glaucoma, when diagnosed, can be treated definitively with iridectomy" 1
Angle-closure glaucoma is the contraindication: The FDA warning specifically states that doxepin "may trigger an angle closure attack in a patient with anatomically narrow angles who does not have a patent iridectomy" 1
This distinction is supported by clinical evidence showing that anticholinergic drugs do not significantly worsen intraocular pressure in treated or untreated open-angle glaucoma 2, 3
Clinical Reasoning
The mechanism of concern does not apply to open-angle glaucoma:
- Doxepin can cause mild pupillary dilation through its anticholinergic effects 1
- Pupillary dilation only triggers angle closure in patients with anatomically narrow anterior chamber angles 4, 1
- Open-angle glaucoma patients have open anterior chamber angles by definition, so pupillary dilation does not obstruct aqueous outflow 5
Important Caveats
Verify the glaucoma diagnosis is truly open-angle:
- Confirm by reviewing gonioscopy results showing open anterior chamber angles 5
- If gonioscopy has never been performed, consider ophthalmology consultation to definitively rule out narrow angles 4
Monitor glaucoma control during treatment:
- Ensure the patient's open-angle glaucoma remains adequately controlled with their current regimen 5
- The concern is not that doxepin will worsen open-angle glaucoma, but rather ensuring baseline glaucoma management is optimized 5
Common Pitfall to Avoid
Many package inserts contain blanket warnings about "glaucoma" without specifying the type, leading to unnecessary medication avoidance in open-angle glaucoma patients 3. The FDA label for doxepin is actually more specific and helpful than most, explicitly stating that open-angle glaucoma is not a risk factor for the angle-closure complications 1.