What's the cause? Really, it's getting at the heart of what's causing the cough - is it post viral cough, reflux, post-nasal drip, etc. You would treat each of them differently. For nonspecific therapy, honey has been shown to be just as effective as most otc meds. Cough meds w/ opiods are probably the most effective (codeine, hycodan) but they come with their own risks - resp depression, constipation.