My 18 day old is on 1 ml of zantac (ranitidine) for 5 days now. she still has the arching of the back and painful cry. how long until meds kick in? new meds?

Wow: That must be some pretty bad reflux. Have you talked to your pediatrician about changing formulas (if your baby is formula fed)? Or maybe, if it hasn't been done yet, an upper GI series (xrays) to find out if the anatomy of the stomach and intestines is ok? Or, if your nursing, maybe something in your diet needs to be changed to decrease the symptoms in your baby. I've seen that help before.

Not a quick fix: Every baby has some reflux & some have more symptoms than others. The backwash of stomach acid produces the equivalent of a sunburn on the inside of the swallowing tube & that hurts. The Zantac (ranitidine) reduces the acidity some but it is not a pain controler. It just gives the gut a better chance to heal. After a week or 2 on meds u should see improvement. Discuss some other things u can try with the dr.