Suntuss Mechanism of Action

Pharmacology: Pharmacodynamics: Dextromethorphan is a cough suppressant. It acts centrally to elevate the threshold for coughing. It has no analgesic effect or sedative effect on the nervous system, nor any other established pharmacological action.
Diphenhydramine hydrochloride is an antihistamine with anticholinergic (drying) and sedative side-effects.
Antihistamines appear to compete with histamine for cell receptor sites on effector cells.
Pharmacokinetics: Dextromethorphan is well absorbed from the gastrointestinal tract. It is metabolised in the liver and excreted as unchanged dextromethorphan and demethylated morphinan compounds.
Diphenhydramine is readily absorbed from the gastrointestinal tract. It is extensively metabolised in the liver and excreted in the urine. Maximum plasma diphenhydramine concentrations ranging from 81 to 159 mg per ml were obtained 2 to 4 hours after administration of diphenhydramine hydrochloride 100 mg by mouth to 4 healthy subjects. The plasma half-life calculated over the period 4 to 24 hours after administration ranged from 5 to 8 hours. Urinary excretion of diphenhydramine metabolites was about 64% of the dose after 96 hours.