Shinallerg Mechanism of Action

Pharmacology: Pharmacodynamics: Antazoline is an anti-histamine of the ethylenediamine class, which are selective H1-antagonist. When used systemically, this group of anti-histamine can cause moderate sedation (despite having weak CNS effects), gastric disturbances, and skin sensitization. Antazoline competitively blocks H1 receptors. Effects mediated by H1 receptors include the contraction of smooth muscle and the dilatation and increased permeability of the capillaries.
Tetrahydrozoline is a sympathomimetic with alpha adrenergic activity. Its vasoconstrictive effect reduces redness and oedema in allergic conjunctivitis.
Antihistamines, which act by blocking the H1 histamine receptor, are highly effective in providing relief of itching but are not very active in relieving the associated redness. The use of products combining an anti-histamine and a vasoconstrictor is well established in the symptomatic relief of allergic eye disease. Tetrahydrozoline has a rapid onset of action and its effect can last for 4 to 8 hours.
Pharmacokinetics: No specific human pharmacokinetic studies have been conducted with this product. However, systemic effects have been reported following topical administration of naphazoline (which is very similar to tetrahydrozoline).