Guaifenesin & Levomenthol When you're suffering from a deep, chesty cough, but still want to get on with your normal daily routine, Benylin Chesty Coughs Non-Drowsy works deep down to loosen phlegm, clear bronchial congestion, and make your cough more productive. What the medicine is for Benylin Chesty Coughs Non-Drowsy is a medicine which is used to help relieve chesty coughs. It contains Guaifenesin (an expectorant) to help loosen mucus (phlegm) from the lungs and make it easier to cough up, and Levomenthol to help you breathe more easily by easing congestion. The medicine is for use in adults and children aged 12 years and over. What the medicine looks like Benylin Chesty Coughs Non-Drowsy is a clear red syrup, available in 150 ml and 300 ml glass bottles.