Myphetane DX (Brompheniramine Maleate / Pseudoephedrine Hydrochloride / Dextromethorphan Hydrobromide) - Description and Clinical Pharmacology

Rx only

DESCRIPTION

Myphetane DX Cough Syrup is a clear, light pink syrup with a butterscotch flavor.

Each 5 mL (1 teaspoonful) contains:

Brompheniramine Maleate, USP. .. .. .. .. .  2 mg

Pseudoephedrine Hydrochloride, USP. .. .. 30 mg

Dextromethorphan Hydrobromide, USP. ..  10 mg

Alcohol 0.95% v/v

In a palatable, aromatic vehicle.

Inactive Ingredients: artificial butterscotch flavor, citric acid anhydrous, dehydrated alcohol, FD&C Red No. 40, glycerin, liquid sugar, methylparaben, propylene glycol, purified water and sodium benzoate. It may contain 10% citric acid solution or 10% sodium citrate solution for pH adjustment. The pH range is between 3.0 and 6.0.

Brompheniramine Maleate, USP
(±)-2- p -Bromo-α-2-(dimethylamino)ethylbenzyl-pyridine maleate (1:1)

Pseudoephedrine Hydrochloride, USP
(+)-Pseudoephedrine hydrochloride

Dextromethorphan Hydrobromide, USP
3-Methoxy-17-methyl-9α, 13α, 14α -morphinan hydrobromide monohydrate

Antihistamine/Nasal Decongestant/Antitussive syrup for oral administration.

CLINICAL PHARMACOLOGY

Brompheniramine maleate is a histamine antagonist, specifically an H₁-receptor-blocking agent belonging to the alkylamine class of antihistamines. Antihistamines appear to compete with histamine for receptor sites on effector cells. Brompheniramine also has anticholinergic (drying) and sedative effects. Among the antihistaminic effects, it antagonizes the allergic response (vasodilation, increased vascular permeability, increased mucus secretion) of nasal tissue. Brompheniramine is well absorbed from the gastrointestinal tract, with peak plasma concentration after single, oral dose of 4 mg reached in 5 hours; urinary excretion is the major route of elimination, mostly as products of biodegradation; the liver is assumed to be the main site of metabolic transformation.

Pseudoephedrine acts on sympathetic nerve endings and also on smooth muscle, making it useful as a nasal decongestant. The nasal decongestant effect is mediated by the action of pseudoephedrine on α-sympathetic receptors, producing vasoconstriction of the dilated nasal arterioles. Following oral administration, effects are noted within 30 minutes with peak activity occurring at approximately one hour.

Dextromethorphan acts centrally to elevate the threshold for coughing. It has no analgesic or addictive properties. The onset of antitussive action occurs in 15 to 30 minutes after administration and is of long duration.