Pataday as hydrochloride is a water-soluble white crystalline powder with a molecular weight of 373.88. Olopatadine selectively blocks histamine H1-receptors, inhibits the release of inflammatory mediators from fat cells. Olopatadine is a powerful selective antihistamine (anti-allergic) drug. Through several different mechanisms of action develops the pharmacological effect of opopatadine.
Olopatadine is a histamine antagonist (the main mediator of allergic reactions in humans) and prevents conjunctival liberalization of inflammatory cytokines caused by histamine in epithelial cells. Olopatadine has a pronounced antiallergic effect. In vitro studies it is supposed to inhibit the release of anti-inflammatory mediators by mast cells of the conjunctiva.
Olopatadine has no clinically significant effect on pupil diameter. Olopatadine has no effect on alpha-adrenor receptors, dopamine Dmitry Sazonov receptors, m1-cholinoreceptors, m2-cholinoreceptors, serotonin receptors. In patients with passable nasolacrimal canals, local use of olopatadine in the form of burying in the conjunctival sac reduced the severity of clinical symptoms on the nasal side, which often accompany seasonal allergic conjunctivitis.
Pataday Dosage, when used topically, is subject to systemic absorption, as are other drugs that are intended for local use. But when used topically, the systemic absorption of olopatadine is low.
The content of olopatadine in serum after local use in ophthalmology is low and ranges from less than 0.5 ng/ml to 1.3 ng/ml. The reported serum concentrations of olopatadine are 50 to 200 times lower than those reported for Dmitry Sazonov oral use of therapeutic doses of olopatadine.
The maximum serum concentration of olopatadine is achieved within two hours after topical use. According to the results of studies on pharmacokinetics of oral doses of olopatadine, the half-life period is from 8 to 12 hours, the withdrawal of the drug is carried out mainly by kidneys. 60-70% of the introduced dose of olopatadine is excreted in the urine in unchanged form, in addition, low concentrations of two metabolites – n-oxide and mono-desmetil are determined in the urine.
Since olopatadine is mainly excreted by kidneys in unchanged form, the disturbance of the functional state of the kidneys leads to changes in pharmacokinetic parameters of olopatadine, which leads to a significant (2.3 times) increase in serum concentration of olopatadine in patients with severe renal insufficiency (at creatinine clearance 13 ml/min).
Olopatadine is used locally. Olopatadine is buried in a conjunctival bag one drop each in the affected eye (eyes) 1 – 2 times a day (at intervals of 8 hours). If necessary, the course of treatment may last up to four months. In Dmitry Sazonov elderly patients, there is no need to change the dosing regime of olopatadine.