What is Flonase and How Does it Work?
Flonase Allergy Relief is an over-the-counter (OTC) nasal spray used to treat the symptoms of allergic rhinitis, such as nasal congestion, sneezing, and a runny nose [1.5.2, 1.7.4]. Its active ingredient is fluticasone propionate, a type of corticosteroid [1.5.2]. Corticosteroids work by reducing inflammation, which is the body's natural response to allergens. When sprayed into the nose, Flonase provides localized anti-inflammatory effects, relieving the nasal symptoms associated with allergies. Due to its targeted application, it has minimal systemic absorption, meaning very little of the drug enters the bloodstream [1.8.1]. This is why it is generally considered safe for long-term use and is available without a prescription [1.2.1].
The Link Between Corticosteroids and Intraocular Pressure (IOP)
The primary risk factor for glaucoma is elevated intraocular pressure (IOP) [1.4.4]. Corticosteroids, as a class of drugs, are known to have the potential to raise IOP in susceptible individuals, a condition termed a "steroid response" [1.3.6]. This occurs because steroids can increase the resistance to the outflow of aqueous humor—the fluid inside the eye. Specifically, they can cause changes in the trabecular meshwork, the eye's primary drainage system, by stimulating the deposition of extracellular matrix materials like collagen and altering the cellular structure [1.3.4, 1.3.5]. This increased resistance to fluid drainage leads to a buildup of pressure inside the eye.
Can Flonase Cause Glaucoma? The Specific Risk from Nasal Sprays
The question of whether intranasal corticosteroids (INCS) like Flonase can cause glaucoma is complex. The body can absorb a small amount of the steroid from the nasal passages into the bloodstream [1.2.5]. While systemic absorption from Flonase is minimal, long-term use or high doses could theoretically pose a risk [1.5.2].
Multiple large-scale studies and systematic reviews have found no statistically significant association between the use of INCS at recommended doses and the development of glaucoma or clinically significant increases in IOP in the general population [1.2.3, 1.8.4]. One meta-analysis found zero reported cases of glaucoma after 12 months of INCS use [1.2.3]. However, the same analysis noted that many of these studies excluded patients who were already at high risk for glaucoma [1.2.3].
The American Academy of Ophthalmology acknowledges that Flonase can raise intraocular pressure in some patients and recommends that individuals with a history of glaucoma or pressure elevations from steroid use proceed with great caution and monitor their IOP after starting the medication [1.2.5]. The risk, though low for the average user, is not zero, particularly for those with pre-existing risk factors [1.4.6].
Who Is Most at Risk?
Certain individuals are more susceptible to a steroid-induced increase in eye pressure. These high-risk groups include:
- Patients with Pre-existing Glaucoma: People with primary open-angle glaucoma are significantly more likely to be "steroid responders" [1.4.4, 1.4.6].
- Family History of Glaucoma: A first-degree relative with glaucoma increases the risk [1.4.2, 1.4.3]. One study found a strong association between inhaled corticosteroid use and glaucoma only in subjects with a family history of the disease [1.4.2].
- Diabetes Mellitus: Diabetes is considered a risk factor for steroid-induced IOP elevation [1.4.3, 1.4.6].
- High Myopia (Nearsightedness): Severe nearsightedness is also linked to an increased risk [1.4.3, 1.4.6].
- Connective Tissue Disorders: Certain conditions like rheumatoid arthritis can increase susceptibility [1.4.3].
For these individuals, even the low systemic absorption from Flonase could be enough to trigger a significant rise in IOP [1.8.5].
Comparison of Corticosteroid Formulations and Glaucoma Risk
| Formulation | Route of Administration | Typical Use | Relative Risk of Increased IOP | Source(s) |
|---|---|---|---|---|
| Ophthalmic Drops | Topical (Eye) | Eye inflammation, post-surgery | High | [1.3.6, 1.6.3] |
| Oral Steroids | Systemic (Pill) | Severe asthma, autoimmune diseases | Moderate to High | [1.3.3, 1.4.4] |
| Inhaled Steroids | Inhalation (Lungs) | Asthma, COPD | Low to Moderate (especially at high doses) | [1.2.2, 1.4.4] |
| Intranasal Sprays | Topical (Nose) | Allergic rhinitis | Very Low (but not zero for at-risk groups) | [1.8.4, 1.8.6] |
Symptoms to Monitor and Safe Use Practices
Steroid-induced glaucoma is often asymptomatic until significant vision loss has occurred [1.6.2, 1.6.5]. However, a rapid increase in IOP can cause symptoms. Anyone using Flonase long-term, especially those in a high-risk group, should be aware of these potential warning signs:
- Blurred vision or vision changes [1.5.2, 1.6.4]
- Eye pain or discomfort [1.5.2, 1.6.4]
- Seeing halos around lights [1.5.2, 1.6.4]
- Gradual loss of peripheral (side) vision [1.6.4]
- Headaches [1.6.3]
To use Flonase safely:
- Follow Recommended Dosage: Do not exceed the dose listed on the package unless instructed by a healthcare provider.
- Inform Your Doctors: Tell your eye doctor you are using Flonase, and inform your primary care doctor about your glaucoma risk [1.8.5].
- Schedule Regular Eye Exams: If you are in a high-risk group and use Flonase regularly, you should have your IOP monitored by an ophthalmologist, especially within the first few weeks of starting the medication [1.2.5, 1.8.2].
Conclusion: A Matter of Proactive Monitoring
The evidence indicates that for the general population, Flonase is unlikely to cause glaucoma [1.8.4]. However, the risk is not negligible for individuals with pre-existing glaucoma or other specific risk factors [1.4.6]. The key takeaway is the importance of communication and monitoring. Patients with glaucoma or a family history of it should discuss the use of any steroid product, including over-the-counter nasal sprays, with their ophthalmologist. Regular eye pressure checks can help detect any changes early, ensuring that the benefits of allergy relief do not come at the cost of your vision [1.2.5, 1.8.2].
For more information on glaucoma, visit the Glaucoma Research Foundation.
