Relestat (Epinastine)

What Is Relestat and What Is It Used For?

Relestat belongs to a class of medications known as ophthalmic antihistamines. Its active ingredient, epinastine hydrochloride, works through a dual mechanism of action that sets it apart from simple antihistamine eye drops. It directly blocks histamine H1 receptors on the conjunctival surface, preventing the allergic cascade that leads to symptoms such as itching and redness. Additionally, epinastine stabilizes mast cells, which are the immune cells responsible for releasing histamine and other inflammatory mediators when exposed to allergens.

Seasonal allergic conjunctivitis is a common condition that affects a significant portion of the global population, with estimates suggesting that up to 40% of people experience some form of ocular allergy during their lifetime. The condition is triggered by airborne allergens such as tree pollen, grass pollen, ragweed, dust mites, and animal dander. When these allergens come into contact with the conjunctiva (the thin, transparent membrane covering the white of the eye and the inner surface of the eyelids), they trigger an immune response in sensitized individuals that results in the characteristic symptoms of itching, redness, watering, and eyelid swelling.

The onset of action of Relestat is rapid, typically within 3 to 5 minutes of instillation, making it particularly useful for acute symptom relief. The duration of effect lasts approximately 8 hours, which supports the twice-daily dosing regimen. Clinical trials have demonstrated that epinastine significantly reduces ocular itching within minutes of administration and maintains its therapeutic effect throughout the dosing interval.

Relestat is indicated specifically for seasonal allergic conjunctivitis, which is the form of eye allergy that occurs during particular times of the year when pollen counts are elevated. It is not intended for the treatment of perennial allergic conjunctivitis (year-round allergy), although some physicians may prescribe it off-label for this purpose. The medication is also not appropriate for treating eye infections, inflammatory conditions unrelated to allergy, or contact lens-related eye irritation.

It is important to understand that Relestat treats symptoms rather than the underlying allergic condition. While it can provide significant relief from ocular discomfort, it does not alter the immune system's response to allergens over the long term. For patients seeking more comprehensive allergy management, additional treatments such as allergen avoidance strategies, oral antihistamines, or allergen immunotherapy may be recommended by their healthcare provider in conjunction with topical ophthalmic therapy.

What Should You Know Before Using Relestat?

Contraindications

Relestat must not be used if you are allergic (hypersensitive) to epinastine hydrochloride or to any of the other ingredients in the formulation. The excipients include benzalkonium chloride (a preservative), disodium edetate, sodium chloride, sodium dihydrogen phosphate dihydrate, sodium hydroxide or hydrochloric acid (for pH adjustment), and purified water. If you have experienced an allergic reaction to any antihistamine medication in the past, discuss this with your doctor before starting treatment with Relestat.

Patients with a known severe corneal disease or damage should exercise particular caution when using Relestat. The phosphate content of the solution (4.75 mg/ml) can, in very rare cases, cause calcification of the cornea in patients with significantly compromised corneal surfaces. This phenomenon, known as corneal calcification or band keratopathy, occurs when calcium phosphate deposits form on a damaged corneal epithelium. If you have a history of corneal dystrophy, recurrent corneal erosion, or any condition that has significantly damaged the surface of your cornea, your doctor will need to carefully assess whether Relestat is appropriate for you.

Warnings and Precautions

Several important precautions should be observed when using Relestat eye drops to ensure safe and effective treatment:

Benzalkonium chloride, the preservative in Relestat, can be irritating to the eyes, particularly in patients with dry eye syndrome or pre-existing corneal surface disorders. If you experience persistent stinging, burning, or pain in the eye after using the medication, discontinue use and contact your healthcare provider promptly. In some cases, preservative-free alternatives may be more appropriate.

To prevent contamination of the dropper tip and the solution, avoid touching the tip of the bottle to your eye, eyelid, fingers, or any other surface. Contaminated eye drops can cause serious eye infections. Always replace the cap tightly after each use.

Pregnancy and Breastfeeding

The safety of Relestat during pregnancy has not been established through adequate and well-controlled clinical studies in pregnant women. Animal reproduction studies are not always predictive of human response, and there is limited data regarding the use of topical ophthalmic epinastine during pregnancy. If you are pregnant, think you may be pregnant, or are planning to have a baby, consult your doctor or pharmacist before using Relestat. Your physician will carefully evaluate whether the potential benefits of treatment justify the possible risks to the developing fetus.

It is unknown whether epinastine or its metabolites are excreted in human breast milk following topical ophthalmic administration. While the systemic absorption of epinastine from eye drops is expected to be minimal, a risk to the nursing infant cannot be completely excluded. Consult your doctor before using Relestat if you are breastfeeding. Your healthcare provider may recommend monitoring the infant for any adverse effects or may suggest an alternative treatment during the breastfeeding period.

Driving and Operating Machinery

Your vision may become temporarily blurred immediately after instilling Relestat eye drops. This is a common and transient effect that typically resolves within a few minutes. You should not drive a vehicle or operate machinery until your vision has returned to normal. Be particularly cautious when driving at night or in low-light conditions, as any residual visual disturbance may be more pronounced in these environments. If you consistently experience prolonged blurred vision after using Relestat, discuss this with your doctor, as it may indicate an underlying issue that requires attention.

How Does Relestat Interact with Other Drugs?

Because Relestat is administered topically to the eye, its systemic absorption is minimal. The low plasma concentrations achieved after ophthalmic administration significantly reduce the potential for systemic drug interactions compared to oral medications. Clinical studies and post-marketing surveillance have not identified any clinically significant drug-drug interactions with topical ophthalmic epinastine.

Nevertheless, there are important practical considerations when using Relestat alongside other ophthalmic preparations. When multiple eye drops are prescribed simultaneously, the order and timing of administration can affect the efficacy of each product. Instilling drops too close together can result in the second drop diluting or washing out the first, reducing its therapeutic effect.

Although systemic drug interactions with Relestat are considered unlikely due to its topical route of administration, it is always good medical practice to inform your doctor or pharmacist about all medications you are currently taking, have recently taken, or plan to take. This includes prescription medications, over-the-counter products, herbal supplements, and vitamins. Providing a complete medication history allows your healthcare team to identify any potential issues and optimize your overall treatment plan.

Patients using multiple classes of ophthalmic medications (for example, antihistamines, anti-inflammatory agents, and glaucoma drops) should work with their ophthalmologist to establish a clear dosing schedule that ensures adequate spacing between different products and maximizes the therapeutic benefit of each.

What Is the Correct Dosage of Relestat?

Always use Relestat exactly as your doctor has prescribed. If you are unsure about any aspect of your treatment, consult your doctor or pharmacist for clarification. Consistent use during the allergy season is important for maintaining symptom control, but treatment should not extend beyond 8 weeks without medical reassessment.

Adults and Adolescents (12 years and older)

Children (under 12 years)

Elderly Patients

How to Apply Relestat Eye Drops

Proper administration technique is essential to maximize the effectiveness of your treatment and minimize the risk of contamination or side effects. Follow these steps carefully each time you use Relestat:

1. Check the seal: If the tamper-evident seal on the bottle neck is broken before first use, do not use the product and return it to your pharmacy.
2. Wash your hands thoroughly with soap and water before handling the eye drop bottle.
3. Tilt your head back and look up toward the ceiling.
4. Gently pull down your lower eyelid with a clean finger to create a small pocket between the eyelid and the eye.
5. Invert the bottle and squeeze gently to release one drop into the pocket created by the lower eyelid. Avoid touching the dropper tip to your eye or any other surface.
6. Release the eyelid and close your eye gently for approximately 30 seconds. Do not blink excessively.
7. Wipe away any excess solution from your cheek with a clean tissue.
8. Replace the cap tightly immediately after use.

If the drop misses your eye, try again with a new drop. If you are treating both eyes, repeat the procedure for the second eye.

Missed Dose

If you forget to use Relestat at the scheduled time, apply the missed dose 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 dosing schedule. Do not apply a double dose to make up for a missed one, as this will not improve symptom control and may increase the risk of side effects such as eye irritation.

Overdose

If you accidentally instill more drops than prescribed, it is unlikely to cause serious harm. The eye can only hold a limited volume of liquid, and excess solution will simply overflow onto the cheek. Apply your next dose at the regular scheduled time. If you are concerned about accidental overuse, contact your doctor or pharmacist for reassurance.

What Are the Side Effects of Relestat?

Like all medicines, Relestat can cause side effects, although not everyone experiences them. Most side effects associated with Relestat are mild, localized to the eye, and transient in nature. The following information categorizes side effects by their frequency of occurrence, based on clinical trial data and post-marketing surveillance reports.

Phosphate-Related Side Effects

Relestat contains phosphates (4.75 mg/ml). In very rare cases, phosphate-containing eye drops have been associated with the development of corneal calcification (calcium phosphate deposits on the cornea) in patients with pre-existing severe corneal damage. This complication, while extremely uncommon, can lead to cloudy patches on the cornea that may affect vision. Patients with significantly compromised corneal integrity should discuss the risks and benefits of using phosphate-containing eye drops with their ophthalmologist.

Reporting Side Effects

If you experience any side effects, including those not listed above, talk to your doctor or pharmacist. You can also report side effects directly to your national medicines regulatory authority (for example, the FDA in the United States, the MHRA in the United Kingdom, or the EMA in Europe). By reporting side effects, you help provide more information about the safety of this medicine and contribute to the ongoing monitoring of drug safety for all patients.

How Should You Store Relestat?

Proper storage of Relestat is essential to maintain the quality, sterility, and effectiveness of the eye drop solution. Incorrect storage can lead to degradation of the active ingredient, microbial contamination, or changes in the solution's pH and osmolarity that could affect both safety and efficacy.

• Temperature: Store at or below 25°C (77°F). Do not refrigerate or freeze the solution unless specifically directed by your pharmacist.
• Light protection: Keep the bottle in its original outer carton when not in use. Epinastine may be sensitive to light exposure, and the carton provides necessary protection from degradation.
• After opening: The bottle must be discarded 28 days after first opening, regardless of how much solution remains. After this period, the preservative system may no longer adequately protect against microbial growth, increasing the risk of eye infection. To help you remember, write the date of first opening on the outer carton.
• Expiry date: Do not use Relestat after the expiry date printed on the bottle label and carton (after "EXP"). The expiry date refers to the last day of that month.
• Visual inspection: Before each use, check the solution for any signs of deterioration such as color change, cloudiness, or visible particles. If the solution appears discolored or contains particles, do not use it and return it to your pharmacy for disposal.
• Child safety: Keep this medicine out of the sight and reach of children.
• Disposal: Do not dispose of medications via the household waste or down the drain. Ask your pharmacist about approved medicine disposal programs in your area. Proper disposal helps protect the environment.

Each bottle of Relestat contains 5 ml of solution in a plastic dropper bottle with a screw cap. When you receive a new bottle, note that it is deliberately only half-full; this is by design to allow proper function of the dropper mechanism and is not an indication of a filling error.

What Does Relestat Contain?

Understanding the full composition of Relestat can be particularly important for patients with known sensitivities to specific excipients. Each component of the formulation serves a specific purpose in ensuring the stability, sterility, and tolerability of the eye drop solution.

Relestat is a clear, colorless solution supplied in a 5 ml white plastic dropper bottle with a screw cap. Each package contains one bottle. The solution has been formulated to be isotonic and buffered to a pH that is compatible with the natural tear film, minimizing irritation upon instillation.

International Brand Names

Relestat is marketed under different brand names across various countries. In the European Economic Area (EEA), the product is approved under the following names:

• Relestat – Austria, Germany, Denmark, Greece, Hungary, Ireland, Luxembourg, Poland, United Kingdom, Spain
• Purivist – Czech Republic, France, Slovakia

The active ingredient and concentration are identical across all brand names. If you are traveling internationally and need to obtain a refill, provide your pharmacist with the generic name (epinastine hydrochloride 0.5 mg/ml ophthalmic solution) to ensure you receive the correct product.