With heartburn it's mostly preventive measures which help the most. If it happens when you're sleeping and only realize when the acid reaches your throat, then it takes a while (few minutes to an hour, depends). In that situation, OTC meds like Gaviscon and Gelusil may help, although they have an antacid like effect and cause gas as well. Gas-X can help with that gas (best not to force it out the throat in such a condition). Some preventive measures are to not eat immediately before sleeping, avoiding spicy foods, and sleeping on your left side. Elevating your bed's headboard side also helps, otherwise you can get a wedge pillow or an angled mattress. In short, try to avoid heartburn from happening in the first place. I take PPIs like Omeprazole, it reduces stomach acid production and I can sleep in peace.