Tramadol and Pepcid for acid reflux?

There is a moderate interaction between both drugs, moderate meaning:

Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.

Interactions between your drugs
Moderate
famotidine traMADol
Applies to: Pepcid AC (famotidine), tramadol

Using famotidine together with traMADol can increase the risk of an irregular heart rhythm that may be serious and potentially life-threatening, although it is a relatively rare side effect. You may be more susceptible if you have a heart condition called congenital long QT syndrome, other cardiac diseases, conduction abnormalities, or electrolyte disturbances (for example, magnesium or potassium loss due to severe or prolonged diarrhea or vomiting). Talk to your doctor if you have any questions or concerns. You should seek immediate medical attention if you develop sudden dizziness, lightheadedness, fainting, shortness of breath, or heart palpitations during treatment with these medications, whether together or alone. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Interaction report:
https://www.drugs.com/interactions-check.php?drug_list=1066-606,2221-0

Pepcid AC is an OTC medication, I suggest you speak to your Dr. and inform him/her about the possibility of taking this OTC medication (Pepcid AC), and further discuss this potential interaction.