Ano ang effective over the counter medicine ninyo for cough?

If I have a really bad cough, I buy Robitussin DM over the counter. I've been using it for years whenever my cough gets worse, and effective naman talaga sya. It easily takes away my phlegm. Though I heard hindi hiyang sa iba that's why they prefer Lagundi. If the cough is really worse, it's always better to consult a physician for proper medication.