The short answer is yes, these medications may counteract each other.
Domedon is not approved by the U.S. Food and Drug Administration (FDA). Therefore, the active ingredients of this product are unknown. In some countries, Domedon contains the active ingredient Domeperidone. Domeperidone is used to treat nausea and increase motility or movement of the digestive tract. Immodium (loperamide) has the opposite effect on the digestive tract. It decreases motility in the small intestines which allows your body to remove nutrients and fluids from the stool.
Patients who are experiencing nausea and diarrhea associated with excessive food intake or bad food choices may want to try a Bismuth Subsalicylate product such as Kaopectate or Pepto-Bismol to relieve these symptoms. This product helps relieve upset stomach, heartburn, nausea, and diarrhea. If diarrhea is still a problem after taking the Bismuth Subsalicylate, Immodium can be taken according to the instructions on the package. If there is severe cramping, blood in the stool, or if the diarrhea does not resolve in about 24 hours consult your physician. Do not take Bismuth Subsalicylate if you have had a severe allergic reaction (rash, hives, difficulty breathing) to aspirin or a nonsteroidal anti-inflammatory drug (NSAID) such as ibuprofen or naproxen, or if you have bleeding problems such as hemophilia, an active bleeding ulcer, or black or bloody stools.