Pharmacology: Dexchlorpheniramine Maleate is an anti-histamine with anti-cholinergic properties. It is capable of producing a slight to moderate sedative effect. It appears to compete with histamine for receptor sites on effector cells and are of value clinically in the prevention and relief of many allergic manifestations. It has been demonstrated that the predominant activity of the optically active isomers of chlorpheniramine is the dextro-isomer. The dextro-isomer is approximately two times more active than the racemic compound. Since dexchlorpheniramine is the dextro-isomer and active moiety of chlorpheniramine, its action and uses are similar to those of chlorpheniramine. Peak blood levels were achieved at an average time of 3 hours after administration. The half life of Dexchlorpheniramine Maleate ranged from 20 to 24 hours. The drug when given is found to be extensively metabolized. The drug and metabolites were primarily excreted in the urine, with 19% of the dose appearing in 24 hours and a total of 34% in 48 hours. Pseudoephedrine is a physiologically active stereoisomer of ephedrine that acts directly on alpha-adrenergic receptors and to a lesser degree, beta-adrenergic receptors. The alpha-adrenergic effects are believed to result from the reduced production of cyclic adenosine 3', 5' monophosphate (cyclic 3',5' AMP) by inhibition of the enzyme adenyl cyclase, whereas beta-adrenergic effects appear to be caused by the stimulation of adenyl cyclase activity. Pseudoephedrine acts on alpha-adrenergic receptors in the nasal mucosa and releases norepinephedrine, hence producing vasoconstriction of the dilated nasal arterioles resulting in shrinkage of swollen nasal mucous membranes, reduction of tissue hyperemia, oedema and nasal decongestion and an increase in nasal airway patency. Drainage of sinus secretions is increased and obstructed eustachian ostia may be opened. Relaxation of bronchial smooth muscle by stimulation of beta-adrenergic receptors may also occur. Following oral administration of 30 mg of pseudoephedrine hydrochloride effects are noted within 30 minutes with peak activity occuring at approximately one hour after administration and the effect persists for 4 to 6 hours. Pseudoephedrine is absorbed from the gastrointestinal tract. It is resistant to metabolism by monoamine oxidase and is largely excreted unchanged in the urine together with small amounts of its hepatic metabolite. It has half-life of several hours; elimination is enhanced and half-life accordingly shorter in acidic urine.