Is mirtazapine safe to use in patients with glaucoma?

Mirtazapine Safety in Glaucoma Patients

Mirtazapine can be used cautiously in patients with open-angle glaucoma under close ophthalmologic supervision, but should be avoided or used with extreme caution in patients with narrow angles or angle-closure glaucoma due to risk of precipitating acute angle closure. 1, 2

Risk Profile by Glaucoma Type

Open-Angle Glaucoma

• Mirtazapine may cause mild pupillary dilation, but this is generally not problematic in patients with established open-angle glaucoma who have undergone definitive treatment (e.g., iridectomy) 1
• Pre-existing open-angle glaucoma is not a risk factor for angle-closure glaucoma, making mirtazapine relatively safer in this population 1
• All patients with glaucoma on antidepressants require rigorous ophthalmologic supervision with regular intraocular pressure monitoring 3

Angle-Closure Glaucoma (Narrow Angles)

• Mirtazapine poses significant risk in patients with anatomically narrow angles who lack a patent iridectomy 1
• A documented case report describes bilateral secondary angle closure in a 55-year-old female after 6 months of mirtazapine use, with raised intraocular pressure and ultrasound biomicroscopic findings showing ciliary body effusion 2
• The pupillary dilation caused by mirtazapine can trigger an acute angle-closure attack in susceptible individuals 1

Clinical Management Algorithm

Pre-Treatment Assessment

• Before initiating mirtazapine, patients should undergo ophthalmologic examination to determine if they are susceptible to angle closure 1
• Baseline documentation should include optic nerve status, visual field testing, and intraocular pressure measurements 3
• Patients with narrow angles should consider prophylactic iridectomy before starting mirtazapine 1

Monitoring During Treatment

• Target intraocular pressure should be maintained approximately 20% lower than baseline measurements 3
• Regular ophthalmologic follow-up is mandatory throughout treatment 3, 4
• Patients should be educated to report immediately if they develop eye pain, vision changes, or swelling/redness around the eye 1

If Angle Closure Occurs

• In the documented case, discontinuation of mirtazapine resulted in opening of the ocular angle, decreased ciliary body edema, and regression of associated cysts 2
• Intraocular pressure was successfully controlled with topical timolol 0.5% after drug discontinuation 2
• Peripheral laser iridotomy is not indicated in secondary angle closure due to ciliary body effusion 2

Important Clinical Considerations

Contraindications and Warnings

• The FDA label specifically warns about angle-closure glaucoma risk, noting that only some people are susceptible to these problems 1
• Patients with severe or unstable glaucoma should have consultation between psychiatry and ophthalmology before initiating therapy 3

Comparison to Other Antidepressants

• Unlike tricyclic antidepressants which have strong anticholinergic effects and should be avoided in glaucoma patients, mirtazapine's mechanism differs 4, 5
• Selective serotonin and noradrenaline reuptake inhibitors have better evidence for safety in glaucoma, though some SSRIs have been associated with intraocular pressure increases 6, 4
• The anticholinergic burden of various psychiatric medications can increase intraocular pressure, with 32.4% of closed-angle glaucoma patients receiving potentially inappropriate anticholinergic prescriptions 7

Special Populations

• Elderly patients warrant particular caution as they have higher rates of undiagnosed narrow angles and are more likely to receive multiple medications with anticholinergic properties 7
• Female patients may have slightly higher risk, as demonstrated in the case report 2

Common Pitfalls to Avoid

• Do not assume all glaucoma is the same - the distinction between open-angle and angle-closure glaucoma is critical for risk assessment 1
• Do not rely solely on patient history - many patients with narrow angles are asymptomatic until an acute attack occurs 1
• Do not prescribe without baseline ophthalmologic evaluation in patients with any glaucoma history or risk factors 3, 1
• Do not continue mirtazapine if signs of angle closure develop (eye pain, vision changes, elevated intraocular pressure) - immediate discontinuation and ophthalmologic consultation are required 2