This study will determine if an interaction occurs between the HIV medicine raltegravir and an antacid. A prior study found an interaction with another medicine like raltegravir called elvitegravir and an antacid. The elvitegravir levels were reduced by half. The same interaction may occur with raltegravir and an antacid based on the structure of this medicine and how it works. When the levels of HIV medications are reduced, people with HIV can "fail" their treatment. The virus can multiply when the drug levels are too low and the medications can stop working. We need to be sure that antacids will not cause this problem with raltegravir.