upright=1, Eye drop of emedastine Emedastine (trade name Emadine) is a second generation

antihistamine Antihistamines are drugs which treat allergic rhinitis, common cold, influenza, and other allergies. Typically, people take antihistamines as an inexpensive, generic (not patented) drug that can be bought without a prescription and provides ...

used in

eye drop Eye drops or eyedrops are liquid drops applied directly to the surface of the eye usually in small amounts such as a single drop or a few drops. Eye drops usually contain saline to match the salinity of the eye. Drops containing only saline ...

s to alleviate the symptoms of

allergic conjunctivitis Allergic conjunctivitis (AC) is Allergic Inflammation, inflammation of the conjunctiva (the membrane covering the white part of the eye) due to allergy. Although allergens differ among patients, the most common cause is hay fever. Symptoms consist ...

. It acts as a H₁ receptor antagonist. It works by blocking the action of

histamine Histamine is an organic nitrogenous compound involved in local immune responses communication, as well as regulating physiological functions in the gut and acting as a neurotransmitter for the brain, spinal cord, and uterus. Discovered in 19 ...

that causes allergic symptoms. It is used in form of the di

fumarate Fumaric acid or ''trans''-butenedioic acid is an organic compound with the formula HO2CCH=CHCO2H. A white solid, fumaric acid occurs widely in nature. It has a fruit-like taste and has been used as a food additive. Its E number is E297. The sa ...

. The emedastine difumarate is a white, crystalline, water-soluble fine powder. Emedastine eye drops is usually applied twice a day to the affected eye. When the patients with allergic conjunctivitis were treated with 0.05% emedastine difumarate ophthalmic solution for six weeks, the signs and symptoms such as redness, itching and swelling of the eyes were relieved. Emedastine appears to be devoid of effects on adrenergic, dopaminergic and serotonin receptors. This drug was developed by

Alcon Alcon Inc. () is a Swiss-American pharmaceutical and medical device company specializing in eye care products. It has a paper headquarters in Geneva, Switzerland but its operational headquarters are in Fort Worth, Texas, United States, where it ...

, which is global medical company specializing in eye care products.

Pharmacodynamics

Emedastine is significantly selective to H₁ histamine receptors ( K_i = 1.3 nM), whereas its affinities for other histamine receptors were low (H₂: K_i = 49067 nM and H₃: K_i = 12430 nM) ub ''in vitro'' study. Topical ocular administration of emedastine inhibits histamine-stimulated vascular permeability in the conjunctiva as a concentration-dependent manner in ''in vitro'' study.

Pharmacokinetics

The human oral bioavailability is approximately 50% and maximum plasma concentration was achieved within 1–2 hours after dosing. Emedastine is mainly metabolized by the liver. There are two primary metabolites: 5-hydroxyemedastine and 6-hydroxyemedastine. They are excreted in the urine as both free and conjugated forms. The 5'-oxoanalogs of 5-hydroxyemedastine, 6-hydroxyemedastine and the ''N''-oxide are also formed as minor metabolites. The elimination half-life of oral emedastine in plasma is 3–4 hours, whereas that of topical emedastine is 10 hours. Approximately 44% of the oral dose is recovered in the urine over 24 hours with only 3.6% of the dose excreted as parent drug.

Contraindications

Emedastine should not be used in patients who are hypersensitive to emedastine or any other excipients of the preparation.

Benzalkonium chloride Benzalkonium chloride (BZK, BKC, BAK, BAC), also known as alkyldimethylbenzylammonium chloride (ADBAC) is a type of cationic surfactant. It is an organic salt classified as a quaternary ammonium compound. ADBACs have three main categories of use: ...

contained in the bottle of emedastine solution can discolor soft

contact lens Contact lenses, or simply contacts, are thin lenses placed directly on the surface of the eyes. Contact lenses are ocular prosthetic devices used by over 150 million people worldwide, and they can be worn to correct vision or for cosmetic ...

es, so people who wear contact lenses should be careful using it.

Adverse events

The most common adverse effect was headache (11%). The other minor adverse effects encountered in less than 5% of patients were

asthenia Weakness is a symptom of many different medical conditions. The causes are many and can be divided into conditions that have true or perceived muscle weakness. True muscle weakness is a primary symptom of a variety of skeletal muscle diseases, ...

, burning or stinging sensation, unpleasant taste, blurred vision, eye dryness and tearing.

References

H1 receptor antagonists Benzimidazoles Ethers Diazepanes Ethanolamines Ethoxy compounds {{respiratory-system-drug-stub