Are there any contraindications for open-angle glaucoma patients taking Topiramate (Topamax) or Phentermine (Adipex)?

From the Guidelines

Topiramate and phentermine should be avoided in patients with open-angle glaucoma due to their potential to worsen the condition. Topiramate carries a significant contraindication as it can cause acute angle-closure glaucoma through a unique mechanism involving supraciliary effusion and anterior displacement of the lens-iris diaphragm, as noted in the primary angle closure preferred practice pattern guidelines 1. While this primarily affects angle-closure risk, it can worsen existing open-angle glaucoma by further compromising outflow. Phentermine, as a sympathomimetic agent, can potentially increase intraocular pressure by dilating the pupil and impairing aqueous humor drainage, which could exacerbate open-angle glaucoma.

For patients with open-angle glaucoma requiring weight management, alternative medications like orlistat, GLP-1 receptor agonists (such as semaglutide), or naltrexone-bupropion combinations would be safer options, as outlined in the standards of medical care in diabetes-2020 1. Similarly, for seizure or migraine management, alternatives to topiramate such as lamotrigine, valproate, or certain beta-blockers should be considered. Any patient with glaucoma who must take either medication should undergo close ophthalmologic monitoring with regular intraocular pressure measurements and visual field testing, in line with the primary open-angle glaucoma preferred practice pattern guidelines 1.

Key considerations for managing open-angle glaucoma include:

• Lowering intraocular pressure to reduce the risk of disease progression, as supported by clinical trials 1
• Monitoring for signs of disease progression, including optic nerve damage and visual field defects 1
• Adjusting treatment as needed to achieve target intraocular pressure levels and prevent further damage 1

From the FDA Drug Label

A syndrome consisting of acute myopia associated with secondary angle closure glaucoma has been reported in patients receiving Topiramate. Symptoms include acute onset of decreased visual acuity and/or ocular pain Ophthalmologic findings can include myopia, anterior chamber shallowing, ocular hyperemia (redness) and increased intraocular pressure. Mydriasis may or may not be present. This syndrome may be associated with supraciliary effusion resulting in anterior displacement of the lens and iris, with secondary angle closure glaucoma. Symptoms typically occur within 1 month of initiating Topiramate therapy In contrast to primary narrow angle glaucoma, which is rare under 40 years of age, secondary angle closure glaucoma associated with topiramate has been reported in pediatric patients as well as adults.

Contraindications for open angle glaucoma and topiramate:

• Topiramate is associated with an increased risk of secondary angle closure glaucoma, which may be a concern for patients with open angle glaucoma.
• The FDA drug label does not explicitly state that open angle glaucoma is a contraindication for topiramate, but it does recommend caution when using topiramate in patients with any form of glaucoma.
• Phentermine is not mentioned in the provided drug labels as having any interaction with open angle glaucoma.
• Patients with open angle glaucoma should be closely monitored for signs of increased intraocular pressure or other ocular adverse events when taking topiramate 2 2.

From the Research

Contraindications for Open Angle Glaucoma and Topiramate or Phentermine

• Topiramate has been associated with an increased risk of angle-closure glaucoma, as reported in studies 3, 4, 5.
• The use of topiramate can lead to bilateral angle closure, choroidal thickening, and induced myopia, which can exacerbate open-angle glaucoma 3, 4.
• Phentermine, when combined with topiramate, has also been linked to bilateral angle closure, as seen in a case report 4.
• There is no direct evidence of contraindications for open-angle glaucoma and phentermine alone, but the combination of phentermine and topiramate may increase the risk of angle-closure glaucoma 4.
• Patients with open-angle glaucoma should be cautious when taking topiramate, and their intraocular pressure should be closely monitored 3, 5.

Key Findings

• Topiramate-induced angle closure is usually bilateral and associated with acute myopia 3.
• The treatment for topiramate-induced angle closure includes replacing topiramate with appropriate medication, strong cycloplegia, and topical steroids 3.
• The risk of angle-closure glaucoma is higher in patients taking topiramate, especially those under 50 years old 5.