Motilium tablets contain the active ingredient domperidone, which is a type of medicine called a dopamine antagonist. It is an antisickness medicine, and has also been used to relieve uncomfortable symptoms of stomach bloating, fullness and reflux in adults, although this use is no longer recommended – see below. Domperidone is also available without a brand name, ie as the generic medicine.
Domperidone works primarily by blocking dopamine receptors found in the upper end of the digestive system. This causes tightening of the muscles at the entry to the stomach, relaxation of the muscles at the exit of the stomach and increased contraction of the muscles in the stomach itself. These actions speed up the passage of food through the stomach into the intestine, which physically helps prevent vomiting and reduces feelings of sickness, bloating and fullness. It also prevents food from flowing the wrong way through the stomach and so prevents reflux (regurgitation of the stomach contents back into the foodpipe).
Domperidone also blocks dopamine receptors found in an area of the brain known as the chemoreceptor trigger zone (CTZ). The CTZ is activated by nerve messages from the stomach when an irritant is present. It is also activated directly by agents circulating in the blood, for example chemotherapy medicines. Once activated, it sends messages to another area of the brain, the vomiting centre, which in turn sends messages to the gut, causing the vomiting reflex. Blocking the dopamine receptors in the CTZ prevents nausea messages from being sent to the vomiting centre. This reduces the sensation of nausea and prevents vomiting.