Benylin Chesty Coughs Non-Drowsy is a medicine that helps to loosen phlegm and clear bronchial congestion, making your cough more productive. It contains guaifenesin, an expectorant that helps to loosen mucus from the lungs, and levomenthol, which helps to ease congestion and make breathing easier. This non-drowsy syrup is suitable for adults and children aged 12 years and over, and is available in a clear red liquid form in 125ml bottles.