For a persistant cough, I would recommned seeing a doctor, even the labels on the cough medicine suggest this.
hie......u can prefer 'tulsi' in this case bcoz i think ur lungs is affected so Tulsi is the best medic to keep ur lungs healthy and keeps u far away from cough and cold........
U just daily early in the morning take 2 leafs of tulsi with little bit honey,this increases ur resistivity power
Try it and TAKE CARE...........
Try Mucinex (Guaifenesin)
Purchase an over-the-counter expectorant. That should help you ou by loosening the mucus. They come in both long-action tablet form and liquid..