Sunex Mechanism of Action

Pharmacology: Diphenhydramine hydrochloride is well absorbed following oral administration but apparently undergoes first-pass metabolism in the liver and only about 40-60% of an oral dose reaches systemic circulation as unchanged diphenhydramine. Following oral administration of a single dose of diphenhydramine, the drug appears in plasma within 15 minutes and peak plasma concentrations are attained within 1-4 hours. Distribution of diphenhydramine into human body tissues and fluids has not been fully characterized. The terminal elimination half-life of diphenhydramine has not been fully elucidated but appears to range from 2.4-9.3 hours in healthy adults. The terminal elimination half-life reportedly is prolonged in adults with liver cirrhosis. Diphenhydramine is rapidly and apparently almost completely metabolized principally to diphenylmethoxyacetic acid which may further undergo conjugation. The drug also undergoes dealkylation to form the N-demethyl and N, N-didemethyl derivatives. Diphenhydramine and its metabolites are excreted principally in urine.
Ammonium chloride, following oral administration, is rapidly absorbed from the GI tract, complete absorption occurring within 3-6 hours. The drug is metabolized in the liver to form urea and hydrochloric acid. Sodium citrate is an alkalinizing agent whose activity depends on conversion to bicarbonate. When oxidative activity is intact, oxidation of the citrate salt is essentially complete and less than 5% of the drug is excreted in urine unchanged.
Actions and Mode or Mechanisms of Action: Diphenhydramine is an ethanolamine-derivative antihistamine. It shares the action and uses of other antihistamines. It is also used as an antifussive for temporary relief of cough caused by minor throat and bronchial irritation such as may occur with common colds or inhaled irritants.
It has been suggested that ammonium chloride may act as an expectorant by reflex stimulation of bronchial mucous glands resulting from irritation of gastric mucosa following oral administration. Sodium citrate is used as a source of bicarbonate when employed as alkalinizing agent.