The remedy, Andrographis paniculata, is being used by Saul Berkovitz, consultant physician at the Royal London Homeopathic Hospital. Not only does it work for the patients for whom he prescribes it, it is also supported by a study that involved 896 patients.
As Berkovitz points out, it's a successful remedy that other doctors should be advocating, especially at a time when we are over-using antibiotics. He says: "It is far too bitter to be used as a syrup, and it must instad by taken as a capsule or tablet. It doesn't work by soothing coughs directly, but it seems to boost immune function."
(Sources: British Medical Journal, 2008; 337: 476; Planta Med, 2004; 70: 293-8).