Pharmaniaga Diphenhydramine Expectorant Mechanism of Action

Ammonium chloride is used as an expectorant.
Diphenhydramine is an ethanolamine derivative with the actions and uses of the histamine H₁-receptor antagonist.
Ammonium chloride is absorbed from the gastro-intestinal tract. The ammonium ion is converted into urea in the liver, the anion thus liberated into the blood stream and extracellular fluid causes a metabolic acidosis and decreases the pH of the urine; this is followed by transient diuresis.
Diphenhydramine is well absorbed from the gastro-intestinal tract, though high first-pass metabolism appears to affect systemic availability. Peak plasma concentrations are achieved about 1 to 4 hourrs after administration by mouth. Diphenhydramine is widely distributed throughout the body including the CNS.
It crosses the placenta and has been detected in breast milk. Diphenhydramine is highly bound to plasma proteins. Metabolism is extensive. Diphenhydramine is excreted mainly in the urine as metabolites, little is excreted as unchanged drug. Excretion is almost complete within 24 hours of administration.