Been taking zantac (ranitidine) 150 for acid reflux once a day for the past 2-3 days. i feel like i'm coming down with a cold, can i take dayquil tablets with it?

I wouldn't.: Over the counter cough and cold medicines have no proven benefit and many side effects. See http://tinyurl.com/osmaxzo Also, if your cold symptoms started after taking the Zantac, (ranitidine) and you have never had it before, I would stop it for now, to be sure that did not play a role in your new symptoms. You can safely use liquid antacids or tablet antacids (like calcium carbonate) for stomach upset.