Alphagan: Uses, Dosage & Side Effects
A selective alpha-2 adrenergic agonist eye drop used to reduce elevated intraocular pressure in open-angle glaucoma and ocular hypertension
Alphagan (brimonidine tartrate) is a prescription eye drop that belongs to the class of alpha-2 adrenergic receptor agonists. It is primarily used to lower elevated intraocular pressure (IOP) in adults with open-angle glaucoma or ocular hypertension. Alphagan works through a dual mechanism—reducing the production of aqueous humor and increasing its drainage from the eye. It may be prescribed alone or in combination with other glaucoma medications such as beta-blocker eye drops, prostaglandin analogs, or carbonic anhydrase inhibitors.
Quick Facts: Alphagan
Key Takeaways
- Alphagan (brimonidine) lowers intraocular pressure by reducing aqueous humor production and increasing uveoscleral outflow, typically reducing IOP by 20–27%.
- Applied as one drop twice daily (approximately 12 hours apart) in the affected eye(s). It can be used alone or with other glaucoma medications.
- Must not be used in neonates and infants under 2 years due to severe CNS depression risk, and is not recommended in children under 12.
- Common side effects include eye irritation, blurred vision, headache, dry mouth, and drowsiness. Most are mild and tend to diminish over time.
- Remove contact lenses before application and wait at least 15 minutes before reinserting due to benzalkonium chloride preservative.
What Is Alphagan and What Is It Used For?
Alphagan contains the active substance brimonidine tartrate, which belongs to a pharmacological class known as alpha-2 adrenergic receptor agonists. These medications work by stimulating specific receptors in the eye that control fluid dynamics, resulting in a reduction of the pressure within the eyeball. Elevated intraocular pressure is the primary modifiable risk factor for glaucoma, a progressive optic neuropathy that can lead to irreversible vision loss if left untreated.
The drug exerts its therapeutic effect through a dual mechanism of action. First, it decreases the production of aqueous humor (the clear fluid that fills the front part of the eye) by the ciliary body. Second, it enhances uveoscleral outflow, which is one of the pathways through which aqueous humor drains from the eye. This combined action typically produces a 20–27% reduction in intraocular pressure from baseline, with the onset of effect occurring within approximately one hour and peak efficacy at around two hours after instillation.
Alphagan is indicated for the treatment of two primary conditions:
- Open-angle glaucoma — The most common form of glaucoma, characterized by gradual blockage of the eye’s drainage channels while the angle between the iris and cornea remains open. This leads to a slow, progressive increase in intraocular pressure and damage to the optic nerve.
- Ocular hypertension — A condition where intraocular pressure is elevated above the normal range (typically above 21 mmHg) but no detectable optic nerve damage or visual field loss has yet occurred. However, ocular hypertension is a major risk factor for developing glaucoma.
Alphagan may be prescribed as a first-line monotherapy when beta-blocker eye drops (such as timolol) are unsuitable or contraindicated—for example, in patients with asthma, COPD, certain cardiac conditions, or a history of intolerance to beta-blockers. It may also be used as add-on therapy in combination with another IOP-lowering medication (including beta-blockers, prostaglandin analogs, or carbonic anhydrase inhibitors) when a single agent does not provide sufficient pressure reduction. According to the European Glaucoma Society (EGS) guidelines, the target IOP should be individualized based on the severity of glaucoma, risk factors for progression, and the patient’s life expectancy.
In clinical trials, brimonidine has demonstrated sustained IOP-lowering efficacy over long-term treatment periods. A landmark study published in the American Journal of Ophthalmology showed that brimonidine provided clinically meaningful IOP reduction comparable to timolol 0.5% over 12 months, with additional potential neuroprotective properties. The Low-Pressure Glaucoma Treatment Study further demonstrated that patients treated with brimonidine had significantly less visual field progression compared to those treated with timolol, suggesting possible neuroprotective benefits beyond IOP reduction.
What Should You Know Before Using Alphagan?
Before beginning treatment with Alphagan, it is essential to have a thorough discussion with your ophthalmologist or prescribing physician about your complete medical history, current medications, and any known allergies. Certain conditions and drug combinations can make Alphagan unsafe or require careful monitoring during treatment.
Contraindications
- You are allergic (hypersensitive) to brimonidine tartrate or any other ingredient in the formulation, including benzalkonium chloride
- You are currently taking monoamine oxidase (MAO) inhibitors (e.g., phenelzine, tranylcypromine, isocarboxazid) or have taken them within the past 14 days
- You are taking certain antidepressant medications that interact with alpha-2 agonists — always inform your doctor about all antidepressant use
- You are breastfeeding, as brimonidine may pass into breast milk
- The patient is a neonate or infant from birth to 2 years of age
Warnings and Precautions
Talk to your doctor before using Alphagan if you have or have previously had any of the following conditions, as they may require dose adjustment, additional monitoring, or alternative therapy:
- Depression or reduced mental capacity — Brimonidine has been associated with depression and CNS effects in some patients
- Cardiovascular disease — Including coronary insufficiency, Raynaud’s phenomenon, orthostatic hypotension, or thromboangiitis obliterans, as brimonidine can affect blood pressure and heart rate
- Cerebrovascular insufficiency — Reduced blood supply to the brain may be exacerbated
- Low blood pressure — Brimonidine may cause further blood pressure reduction
- Liver or kidney problems — These organs are involved in metabolizing and excreting the drug, and impaired function may lead to increased systemic exposure
Alphagan is contraindicated in neonates and infants (birth to 2 years) due to reports of serious adverse events including CNS depression, apnea, bradycardia, hypothermia, and hypotension. It is not recommended for children aged 2–12 years due to a high incidence of somnolence (up to 25% in clinical studies). It should generally not be used in adolescents aged 12–17 years as clinical studies have not been conducted in this age group.
Pregnancy and Breastfeeding
If you are pregnant, think you may be pregnant, or are planning to become pregnant, consult your doctor before using Alphagan. Animal reproductive studies have not demonstrated fetal harm, but there are no adequate and well-controlled studies in pregnant women. Alphagan should not be used during pregnancy unless the potential benefit to the mother justifies the potential risk to the fetus.
Breastfeeding: Alphagan must not be used while breastfeeding. It is not known whether brimonidine is excreted in human breast milk, but given the drug’s potential for serious adverse effects in nursing infants—particularly CNS depression—breastfeeding is contraindicated during treatment. If treatment is necessary, breastfeeding should be discontinued.
Driving and Operating Machinery
Alphagan can cause blurred vision, visual disturbances, drowsiness, and fatigue in some patients. These effects may be more pronounced at night or in reduced lighting conditions. If you experience any of these symptoms, do not drive or operate machinery until they have resolved. You are responsible for assessing whether you are fit to perform activities that require concentration and alertness.
Important Information About Contact Lenses
Alphagan contains benzalkonium chloride (0.05 mg/ml) as a preservative. This compound can be absorbed by soft contact lenses and may cause discoloration of the lenses. You should remove contact lenses before applying the eye drops and wait at least 15 minutes before reinserting them. Benzalkonium chloride may also irritate the eyes, particularly if you have dry eye syndrome or corneal disorders. If you experience irritation, stinging, or pain after using Alphagan, contact your doctor promptly.
How Does Alphagan Interact with Other Drugs?
Drug interactions with Alphagan can occur through several mechanisms, including pharmacodynamic effects (additive or opposing actions on the same physiological systems) and pharmacokinetic effects (altered absorption, distribution, metabolism, or excretion). Although topical ophthalmic administration results in relatively low systemic exposure, clinically relevant interactions can still occur, particularly in patients using multiple medications.
Always inform your doctor or pharmacist about all medications you are currently taking, have recently taken, or plan to take, including prescription drugs, over-the-counter medications, and herbal supplements. This is especially important if any of your medications are changed or their doses are adjusted during Alphagan treatment.
| Interacting Drug/Class | Severity | Effect | Recommendation |
|---|---|---|---|
| MAO inhibitors (phenelzine, tranylcypromine) | Contraindicated | Risk of hypertensive crisis and severe cardiovascular events | Do not use together. Wait 14 days after stopping MAO inhibitors. |
| Tricyclic antidepressants (amitriptyline, nortriptyline) | Major | May reduce the hypotensive effect of brimonidine and increase CNS depression | Avoid combination or use with close monitoring. |
| CNS depressants (opioids, benzodiazepines, barbiturates, alcohol) | Major | Enhanced sedation, drowsiness, and impaired psychomotor function | Use caution. Avoid alcohol. Monitor for excessive sedation. |
| Antihypertensives / cardiac glycosides | Moderate | Additive blood pressure lowering; may exacerbate orthostatic hypotension | Monitor blood pressure and heart rate regularly. |
| Beta-blockers (timolol eye drops) | Moderate | Additive IOP reduction but also additive cardiovascular effects | Combination is therapeutic but monitor heart rate and blood pressure. |
| Methylphenidate / chlorpromazine / reserpine | Moderate | May affect metabolism or interfere with alpha-2 receptor signaling | Use with caution; inform your doctor. |
| Alpha-receptor agonists/antagonists (isoprenaline, prazosin) | Moderate | Competition for the same receptor may reduce or alter therapeutic effect | Avoid concurrent use if possible. |
| General anesthetics | Moderate | Enhanced cardiovascular depression during surgical procedures | Inform your anesthesiologist before any surgical procedure. |
When using Alphagan together with other eye drops, allow an interval of 5–15 minutes between instillation of each medication. This prevents the second drop from washing out the first before adequate absorption has occurred. Eye drops should generally be applied before eye ointments or gels, as the thicker formulations can create a barrier to absorption.
What Is the Correct Dosage of Alphagan?
Always use Alphagan exactly as your doctor has instructed. If you are unsure about any aspect of your treatment, consult your ophthalmologist or pharmacist. Consistent adherence to the prescribed dosage schedule is essential for maintaining stable intraocular pressure control and preventing glaucoma progression.
Adults
Standard Adult Dosage
One drop of Alphagan 0.2% (2 mg/ml) in the affected eye(s) twice daily, with approximately 12 hours between doses (e.g., morning and evening). Do not change the dose or stop using Alphagan without first speaking to your doctor, as abrupt discontinuation may lead to a rebound increase in intraocular pressure.
Children
Pediatric Use
- Under 2 years: Contraindicated — must not be used.
- 2–12 years: Not recommended due to safety concerns (high incidence of somnolence).
- 12–17 years: Generally not recommended as clinical studies have not been conducted in this age group.
Elderly Patients
Elderly (65 years and older)
No specific dose adjustment is required for elderly patients. However, older adults may be more susceptible to systemic side effects such as drowsiness, hypotension, and dizziness. Blood pressure and heart rate should be monitored, particularly at the start of treatment. Patients with renal or hepatic impairment should be closely observed.
How to Apply Eye Drops
Proper application technique is crucial for ensuring the medication reaches the eye effectively while minimizing systemic absorption and potential side effects. Follow these steps carefully:
- Wash your hands thoroughly before handling the eye drop bottle.
- Tilt your head back and look upward toward the ceiling.
- Gently pull down the lower eyelid to create a small pocket.
- Hold the bottle upside down and squeeze gently until one drop falls into the pocket formed by the lower eyelid.
- Release the lower eyelid, close your eye, and press your finger gently against the inner corner of the eye (near the nose) for about 1 minute. This technique (nasolacrimal occlusion) reduces systemic absorption through the nasolacrimal duct.
- If the drop misses the eye, try again with a new drop.
- Do not let the bottle tip touch the eye, eyelid, fingers, or any other surface to avoid contamination.
- Replace and tighten the cap immediately after use.
Missed Dose
If you forget a dose, apply it as soon as you remember. However, if it is almost time for your next scheduled dose, skip the missed dose and continue with your regular routine. Do not apply a double dose to make up for a forgotten one. Maintaining a consistent 12-hour interval between doses is ideal for optimal IOP control.
Overdose
In adults: Excessive topical application may cause the known side effects of brimonidine, including drowsiness, hypotension, and bradycardia. Accidental oral ingestion has been associated with blood pressure changes (initial hypotension followed by hypertension in some cases).
In children: Accidental ingestion in children has caused serious adverse events including severe drowsiness, flaccidity, hypothermia, pallor, and respiratory depression. These can be life-threatening. If a child accidentally ingests Alphagan, seek emergency medical care immediately.
Contact your doctor, hospital, or poison control center immediately if overdose is suspected.
What Are the Side Effects of Alphagan?
Like all medicines, Alphagan can cause side effects, although not everybody gets them. The side effects are categorized below by how frequently they occur and whether they affect the eye or the rest of the body. Most ocular side effects are mild to moderate and tend to diminish as your body adjusts to the medication. However, if any side effect becomes severe, persistent, or bothersome, contact your doctor promptly.
Eye-Related Side Effects
Very Common
May affect more than 1 in 10 users
- Eye irritation (redness, burning, stinging, foreign body sensation, itching)
- Follicles or white spots on the conjunctiva (clear membrane covering the eye)
- Blurred vision
- Allergic reaction in the eye
Common
May affect up to 1 in 10 users
- Local irritation (eyelid inflammation, swelling of conjunctiva)
- Sticky eyes, eye pain, increased tearing
- Light sensitivity (photophobia)
- Corneal erosion and discoloration
- Dry eyes
- Conjunctival blanching (whiteness)
- Abnormal vision
- Conjunctivitis (inflammation of the conjunctiva)
Very Rare
May affect up to 1 in 10,000 users
- Iritis (inflammation within the eye)
- Miosis (reduced pupil size)
Not Known
Frequency cannot be estimated
- Eyelid itching (pruritus)
Systemic (Whole-Body) Side Effects
Very Common
May affect more than 1 in 10 users
- Headache
- Dry mouth
- Fatigue / drowsiness
Common
May affect up to 1 in 10 users
- Dizziness
- Common cold symptoms (upper respiratory infection)
- Gastrointestinal symptoms (nausea, upset stomach)
- Taste disturbance
- Weakness (asthenia)
Uncommon
May affect up to 1 in 100 users
- Depression
- Palpitations or changes in heart rate
- Nasal dryness
- Generalized allergic reactions
Rare
May affect up to 1 in 1,000 users
- Shortness of breath (dyspnea)
Very Rare
May affect up to 1 in 10,000 users
- Insomnia
- Syncope (fainting)
- Hypertension (high blood pressure)
- Hypotension (low blood pressure)
Not Known
Frequency cannot be estimated
- Skin reactions including redness, facial swelling, itching, rash, and vasodilation
Contact your doctor immediately if you experience severe allergic reactions (facial swelling, difficulty breathing, widespread rash), significant changes in heart rate or blood pressure, severe eye pain, sudden vision changes, or signs of depression. If you suspect an allergic reaction to the eye drops, stop use and consult your ophthalmologist as an alternative medication may be more appropriate.
Long-term studies have shown that some patients may develop a delayed allergic reaction to brimonidine, typically appearing after several months of use. This manifests as a follicular conjunctival response, eyelid dermatitis, and ocular pruritus. If this occurs, your doctor will likely switch you to an alternative IOP-lowering medication. The allergic reaction typically resolves completely after discontinuation of brimonidine.
How Should You Store Alphagan?
Proper storage of Alphagan is essential to maintain the medication’s potency and sterility throughout its shelf life. Eye drops are particularly susceptible to contamination and degradation if not stored correctly, which could reduce their effectiveness or introduce infection risk.
- Temperature: Store at or below 25°C (77°F). Do not freeze.
- Light: Keep the bottle in its outer carton when not in use to protect from light.
- Children: Store out of the sight and reach of children.
- Seal: Do not use the bottle if the tamper-evident seal around the cap is broken before first use.
- Expiry: Do not use after the expiry date stated on the label and carton (the expiry date refers to the last day of that month).
- After opening: Discard the bottle 28 days after first opening, even if there is solution remaining. Write the date you first open the bottle on the label to help you remember.
Do not dispose of medicines in wastewater or household waste. Return unused or expired medication to a pharmacy for safe disposal. This helps protect the environment and prevents accidental exposure.
What Does Alphagan Contain?
Understanding the composition of Alphagan is important for identifying potential allergens and for understanding why certain precautions (such as contact lens removal) are necessary.
| Component | Role | Amount |
|---|---|---|
| Brimonidine tartrate | Active ingredient | 2.0 mg/ml (equivalent to 1.3 mg/ml brimonidine) |
| Benzalkonium chloride | Preservative | 0.05 mg/ml |
| Polyvinyl alcohol | Viscosity agent (aids retention on eye surface) | As required |
| Sodium chloride | Tonicity agent (osmotic balance) | As required |
| Sodium citrate | Buffering agent | As required |
| Citric acid monohydrate | Buffering agent / pH regulator | As required |
| Purified water | Vehicle / solvent | To volume |
| Sodium hydroxide / hydrochloric acid | pH adjustment | As required |
Physical appearance: Alphagan 0.2% eye drops is a clear, green-yellow to slightly green-yellow solution supplied in a plastic dropper bottle. Each bottle contains either 2.5 ml, 5 ml, or 10 ml of solution. The product is available in pack sizes of 1, 3, or 6 bottles (not all pack sizes may be marketed in all countries).
Preservative-free alternatives: For patients who are sensitive to benzalkonium chloride or who require long-term treatment with multiple preserved eye drops, preservative-free formulations of brimonidine (such as Alphagan P, which uses Purite as a milder preservative) may be available in some markets. Discuss these options with your ophthalmologist if you experience significant ocular surface irritation.
Frequently Asked Questions About Alphagan
Alphagan (brimonidine tartrate) is a prescription eye drop used to lower elevated intraocular pressure (IOP) in patients with open-angle glaucoma or ocular hypertension. It can be used as monotherapy when beta-blocker eye drops are unsuitable, or as add-on therapy when a single medication is insufficient to control IOP. Brimonidine works by reducing the production of aqueous humor and increasing its drainage from the eye, typically producing a 20–27% reduction in eye pressure.
Alphagan contains brimonidine, a selective alpha-2 adrenergic receptor agonist. It works through a dual mechanism: first, it reduces the production of aqueous humor (the fluid inside the eye) by acting on alpha-2 receptors in the ciliary body; second, it increases uveoscleral outflow, one of the pathways through which fluid drains from the eye. The onset of action is approximately 1 hour, peak effect occurs at 2 hours, and the duration of IOP-lowering effect is approximately 12 hours, which is why it is typically dosed twice daily.
Alphagan must not be used in neonates and infants from birth to 2 years of age due to serious safety concerns including CNS depression, apnea, bradycardia, hypothermia, and hypotension. It is not recommended for children aged 2–12 years because of a high incidence of drowsiness (up to 25% in clinical studies). It should generally not be used in adolescents aged 12–17 years as clinical studies have not been conducted in this age group. If a child requires glaucoma treatment, your pediatric ophthalmologist will recommend a safer alternative.
Alphagan contains benzalkonium chloride as a preservative, which can be absorbed by soft contact lenses and may cause lens discoloration. You should remove your contact lenses before applying the eye drops and wait at least 15 minutes before reinserting them. If you experience persistent eye irritation, stinging, or pain while using Alphagan with contact lenses, contact your eye doctor. In some markets, preservative-free formulations (such as Alphagan P with Purite) may be available and may be better tolerated by contact lens wearers.
Alphagan should be stored at or below 25°C (77°F) and kept out of the reach of children. Once opened, the bottle must be discarded after 28 days, even if there is solution remaining, because the preservative cannot guarantee sterility indefinitely after the seal is broken. Write the opening date on the bottle to help you track this. Do not use the product past its printed expiry date or if the seal was already broken when you received it.
If you accidentally apply more drops than prescribed, you may experience known side effects of brimonidine such as increased drowsiness, dry mouth, or low blood pressure. In most cases, these effects are temporary. However, if you or someone else (especially a child) accidentally swallows the eye drops, seek emergency medical attention immediately. In children, accidental oral ingestion has been associated with serious adverse events including severe drowsiness, hypothermia, pallor, flaccidity, and breathing difficulties. Contact your doctor, emergency department, or poison control center right away.
References
- European Medicines Agency (EMA). Alphagan – Summary of Product Characteristics. Last updated 2025. Available at: www.ema.europa.eu
- U.S. Food and Drug Administration (FDA). Alphagan P (brimonidine tartrate ophthalmic solution) – Prescribing Information. Revised 2024. Available at: www.fda.gov
- American Academy of Ophthalmology (AAO). Preferred Practice Pattern: Primary Open-Angle Glaucoma. 2025. Available at: www.aao.org
- European Glaucoma Society (EGS). Terminology and Guidelines for Glaucoma, 5th Edition. 2024. Available at: www.eugs.org
- Krupin T, Liebmann JM, Greenfield DS, et al. A Randomized Trial of Brimonidine Versus Timolol in Preserving Visual Function: Results from the Low-Pressure Glaucoma Treatment Study. American Journal of Ophthalmology. 2011;151(4):671–681. doi:10.1016/j.ajo.2010.09.026
- World Health Organization (WHO). Model List of Essential Medicines. 23rd List, 2023. Available at: www.who.int
- British National Formulary (BNF). Brimonidine tartrate – Monograph. Updated 2025. Available at: bnf.nice.org.uk
- Weinreb RN, Aung T, Medeiros FA. The Pathophysiology and Treatment of Glaucoma: A Review. JAMA. 2014;311(18):1901–1911. doi:10.1001/jama.2014.3192
- Tham YC, Li X, Wong TY, et al. Global prevalence of glaucoma and projections of glaucoma burden through 2040: a systematic review and meta-analysis. Ophthalmology. 2014;121(11):2081–2090. doi:10.1016/j.ophtha.2014.05.013
- National Institute for Health and Care Excellence (NICE). Glaucoma: diagnosis and management. NICE guideline [NG81]. Updated 2024. Available at: www.nice.org.uk
Editorial Team
Medical Content
iMedic Medical Editorial Team – Specialists in Ophthalmology and Clinical Pharmacology
Medical Review
iMedic Medical Review Board – Independent review according to international guidelines (WHO, EMA, FDA, AAO, EGS)
Evidence Framework
GRADE methodology – Evidence Level 1A based on systematic reviews and randomized controlled trials
Last Reviewed
– Content verified against current EMA SmPC and FDA label
This article was prepared based on the approved Summary of Product Characteristics (SmPC) for brimonidine tartrate, peer-reviewed clinical literature, and international ophthalmology guidelines. All medical facts have been independently verified. iMedic receives no commercial funding and has no conflicts of interest.