I've taken Lasix for many years and have never had burping as a side effect. I wonder if he may be somehow eating or drinking a little different to where he is swallowing air. I'm glad the Pepcid made him feel better.
What are the possible side effects of Lasix
Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat. Stop using Lasix and call your doctor at once if you have any of these serious side effects:
dry mouth, thirst, nausea, vomiting;
feeling weak, drowsy, restless, or light-headed;
fast or uneven heartbeat;
muscle pain or weakness;
urinating less than usual or not at all;
easy bruising or bleeding, unusual weakness;
a red, blistering, peeling skin rash;
hearing loss; or
nausea, stomach pain, low fever, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes).
Less serious side effects may include:
diarrhea, constipation, or stomach pain;
headache;
numbness, burning, pain, or tingly feeling;
dizziness; or
blurred vision.
This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect.