I have this condition as well.7 weeks  ago took a terrible cold/catarrah, have been terrible with post nasal drip  Went through 2 bottles of Adult Meltus for chesty coughs Then went to  doctor who  prescribed  me with antibiotics and prednisone for a week still bothered with it then tried Benylin for a week Still no joy.it.Then last week I bought Robitussin +congestion from Boots Chemist took 10ml 4 times a day and at last I am beginning to feel better Catarrah has thinned out and have stopped coughing so much I would definately recommend this one