Dextromethorphan 10 mg + Chlorpheniramine maleate 2 mg + Phenylephrine 5 mgTruquil

How Truquil works

This is a combination, and each component handles a different part of the problem. Chlorpheniramine acts on the H1 receptor and also enters the brain, which dries the secretions behind a runny nose and produces a calming, sedating effect. In a cold preparation that mild sedation is part of the intention, since it helps the person rest through the night. Phenylephrine narrows the swollen blood vessels in the lining of the nose. It is that swelling, not mucus alone, that blocks the nose during a cold, so shrinking the lining opens the airway and relieves the stuffiness and sinus pressure. Dextromethorphan acts to suppress cough. The target is a dry, unproductive cough, where coughing serves no purpose and only irritates the throat into more coughing. It works by raising the threshold of the cough centre in the brainstem, so minor throat irritation no longer sets the reflex off. Combining them means one preparation covers what would otherwise need two or three.