Optihist Plus Eye Drop

Allergic conjunctivitis is one of the most common eye conditions and is triggered by allergens such as pollen, dust, pet dander, or mould. When the conjunctiva (the thin membrane covering the white of the eye and lining the inner eyelid) comes into contact with an allergen, mast cells release histamine and other inflammatory mediators, causing itching, redness, watering, and swelling. Non-allergic irritation from smoke, air conditioning, or screen use can produce similar symptoms.

Chlorpheniramine maleate is a first-generation antihistamine. On topical application, chlorpheniramine blocks histamine H1 receptors on conjunctival nerve endings, reducing the itching and watering caused by histamine.

Tetrahydrozoline is a sympathomimetic agent that acts on alpha-adrenergic receptors in the small blood vessels of the conjunctiva. By stimulating these receptors, it constricts the vessels and rapidly reduces redness. It does not treat the underlying allergy or inflammation — its action is symptomatic.

Boric acid is a mild antiseptic with weak antibacterial and antifungal activity. In ophthalmic preparations, its main role is as a buffer to maintain the formulation at a comfortable pH close to that of natural tears, with secondary mild antiseptic action. Sodium chloride keeps the formulation isotonic with tear fluid, preventing the discomfort caused by drops that are too dilute or too concentrated.

• Symptomatic relief of allergic conjunctivitis, which manifests as itchy, red, watery eyes from pollen, dust, or other allergens.

• Temporary relief of eye redness due to minor irritation from smoke, dust, wind, or screen use.

• Short-term symptomatic comfort in mild non-infective eye irritation.

• Combination of an antihistamine (anti-allergic), a vasoconstrictor (blood vessel narrowing agent), a mild antiseptic, and an isotonic vehicle for comprehensive symptom relief.

• Rapid reduction of redness from tetrahydrozoline.

• Reduces itching and watering through chlorpheniramine.

• Buffered, isotonic formulation is comfortable on the eye.

• Available over-the-counter for short-term symptomatic use.

Common:

• Brief stinging or burning on instillation
• Temporary blurring of vision
• Mild dryness in the eyes

Uncommon:

• Eyelid itching or contact dermatitis
• Mild headache
• Dilated pupils with frequent or prolonged use

Serious side effects requiring immediate attention:

• Rebound redness, which would cause worsening of eye redness when the drops are stopped after prolonged use
• Severe allergic reaction
• Eye pain, marked visual loss, or severe photophobia
• Acute angle-closure glaucoma signs, such as eye pain, halos around lights, nausea, and vomiting

To use Optihist Plus Eye Drop, wash your hands. Tilt your head back, look up, and gently pull down the lower eyelid to form a small pocket. Hold the bottle above the eye, close to but not touching the eye or lashes, and instil one or two drops into the pocket. Close your eyes gently for a minute and press lightly on the inner corner of the eye to reduce drainage into the nose. Use only as needed for symptomatic relief, and do not use continuously for more than 3 to 5 days without medical advice. This is because prolonged use of decongestant drops can cause rebound redness.

Chlorpheniramine blocks H1 histamine receptors on conjunctival sensory nerve endings. Histamine, released by mast cells (immune cells) during an allergic reaction, normally binds to these receptors and triggers itching, watering, and vasodilation (widening of blood vessels). By blocking H1 receptors, chlorpheniramine prevents these signals from being generated, reducing the itch–scratch–tear cycle of allergic eye disease.

Tetrahydrozoline acts as an alpha-adrenergic agonist. The small arterioles of the conjunctiva have alpha-1 receptors on their smooth muscle walls; when stimulated, the smooth muscle contracts and the vessels narrow. This reduces the amount of blood passing through the conjunctival vessels and rapidly reduces visible redness.

Boric acid maintains the solution at a slightly acidic pH similar to natural tears, which is the most comfortable pH range for the ocular surface. Sodium chloride keeps the osmotic concentration matched to tear fluid, so the drops do not cause discomfort by drawing water into or out of corneal cells.

Optihist Plus Eye Drop has no clinically significant food interactions when used topically in the eyes.

• MAOIs (SEVERE): Adding tetrahydrozoline to MAOI therapy (used for the management of depressive disorders) can cause a dangerous spike in blood pressure.

• Tricyclic antidepressants (CAUTION): Amplify tetrahydrozoline's effect on heart rate and blood pressure.

• Other sympathomimetic drugs (CAUTION): Decongestants, cold medicines, and similar drugs add to the same cardiovascular effects.

• Other anticholinergic drugs (CAUTION): Combining with chlorpheniramine can worsen dry mouth, blurred vision, and urinary retention.

• Narrow-angle or angle-closure glaucoma (CONTRAINDICATED): Vasoconstrictors can precipitate acute angle-closure. The drops slightly dilate the pupil, which can block fluid drainage in narrow-angled eyes and trigger a painful, sight-threatening pressure spike.

• Active ocular infection (CONSULT YOUR DOCTOR): These drops do not treat infection. Masking the redness can hide an infection that needs proper antibiotic treatment instead.

• Severe cardiovascular disease, hypertension, hyperthyroidism, or diabetes (CAUTION): Small amounts of tetrahydrozoline can enter the bloodstream and raise heart rate or blood pressure, which can be problematic in these conditions.

• Recent eye surgery (CAUTION): Healing tissues are more sensitive, and vasoconstrictors can hamper the blood flow to the recovering eye. Therefore, consult with your doctor before use.

• Dry eye disease (CAUTION): Vasoconstrictors reduce conjunctival blood flow, which can worsen dryness with prolonged use.

Accidental ingestion of Optihist Plus Eye Drop, especially by children, can cause serious systemic effects, which can manifest as drowsiness, slow heart rate, low blood pressure, low body temperature, and, in severe cases, coma. Keep this product safely out of reach of children. Suspected ingestion requires urgent medical attention.

This product is used as needed for symptom relief. If you forget a dose, simply apply it when symptoms occur. Do not use more than directed to make up for a missed dose.