|Systematic (IUPAC) name|
|Molecular mass||302.415 g/mol|
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Emedastine (trade name Emadine) is a second generation antihistamine used in eye drops to treat allergic conjunctivitis. It acts as a H1 receptor antagonist. It works by blocking certain natural substances, histamines that cause allergic symptoms. It is used in form of the difumarate. The formation of emedastine difumarate is a white, crystalline, water-soluble fine powder. Emedasine is applied as an eye drop with 2 times a day. When the patients with allergic conjunctivitis were treated with 0.05% emedastin 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 which is global medical company specializing in eye care products.
Emedastine is significantly selective to H1 histamine receptors (Ki=1.3 nM), whereas its affinities for other histamine receptor are low (H2: Ki=49067 nM and H3: Ki=12430 nM ) in vitro study. Tropical ocular administration of emedastine inhibits histamine-stimulated vascular permeability in the conjunctiva as a concentration dependent manner in vitro study.
The human oral bioavailability is approximately 50% and maximum plasma concentration were 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 and 6-hydroxy-emedastine 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.
Emedastine should not be used in patients who are hypersensitive to any other ingredients or emedastin. Benzalkonium chloride contained in the bottle of emedastines can discolor soft contact lenses, so people who wear the lenses should be careful with using it. The most common adverse effect was headache (11%). The other minor adverse effect less than 5% of patients: asthenia, burning or stinging, bad taste, blurred vision, dry eye and tearing.
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