Loperamide is a drug that belongs to the class of opioids and is used to treat diarrhea. It is on the list of essential medicines of the WHO (World Health Organization).
What is loperamide?
The drug loperamide was first synthesized by Paul Janssen for Janssen Pharmaceutica. From a chemical point of view, loperamide is a diphenyl piperidine. It belongs to the sham opioids. The first clinical study with the active ingredient was published in 1973 in an American specialist magazine. In the same year loperamide was launched and is still available under the trade name Imodium®.
Loperamide has also been available on the German market since 1976. In Germany it is the most frequently sold, non-prescription remedy for diarrhea. It is recommended for the symptomatic treatment of acute diarrhea. The drug is administered orally and is also contained in some combination preparations together with the active ingredient simeticon. Loperamide is only available from pharmacies in all available forms.
Pharmacological effect
Loperamide hydrochloride binds to the µ-opioid receptors in the myenteric plexus. The myenteric plexus, also known as the Auerbach plexus, runs through almost the entire musculature of the gastrointestinal tract. It is part of the enteric nervous system (ENS) and regulates the peristalsis of the intestine. It also regulates the secretion of digestive enzymes into the bowel.
Loperamide reduces the activity of the smooth muscles of the intestinal wall via the µ-opioid receptors. In particular, the longitudinal and circular small intestine muscles are inhibited in their activity. Due to the weakened peristalsis, the intestinal contents remain in the small intestine longer. The intestinal contents are in contact with the mucous membrane of the small intestine over a longer period of time, so that electrolytes and fluids can be absorbed more. The chair becomes firmer. Loperamide also increases muscle tension in the anal sphincter. This improves stool continence.
Since loperamide cannot cross the blood-brain barrier, it does not reach the opioid receptors and is therefore counted among the sham opioids. Loperamide is only effective locally.
Medical application & use
The main indications for the use of loperamide are diarrhea of all kinds. The agent is taken orally for travelers' diarrhea, unspecific diarrhea, diarrhea caused by irritable bowel syndrome or diarrhea caused by disorders of the intestinal peristalsis.
Under medical supervision, loperamide is also used to treat diarrhea caused by cytostatics or so-called protease inhibitors as part of chemotherapeutic treatment. In combination with the active ingredient simeticone, loperamide is administered for acute diarrhea with abdominal cramps.
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➔ Medication for diarrheaRisks & side effects
It should be noted that loperamide only has a symptomatic effect and therefore does not fight the cause of the diarrheal disease. Although it can help to stop the loss of fluid and electrolytes, it should only be taken for a short time in the case of a known underlying disease or in parallel with a causal therapy.
Loperamide is not suitable for the treatment of infectious diarrheal diseases. These are usually noticeable as mucus, blood or pus in the stool. Loperamide calms the intestines and extends the intestinal passage. This effect is desirable for some diarrheal diseases, but for infectious dysentery it increases the duration of the pathogen's stay in the intestine. While the pathogens remain in the intestine, they can continue to release toxins into the intestine. This can be particularly dangerous when infected with enterohaemorrhagic E. coli (EHEC). The haemolytic uremic syndrome (HUS) can be triggered by the toxins.
Loperamide should also not be used in acute flare-ups of the inflammatory bowel disease ulcerative colitis. Further contraindications are pseudomembranous colitis, the use of broad spectrum antibiotics and all diseases in which the intestinal peristalsis is pathologically inhibited. These include the intestinal obstruction (ileus), the megacolon and the toxic megacolon.
In general, loperamide is very well tolerated. However, disrupting bowel movements can cause abdominal pain, nausea and constipation. The abdomen may be bloated. If there is no improvement in acute diarrhea within 48 hours of taking loperamide, a doctor must be consulted. Longer use should only take place after consulting a doctor.
Normally, loperamide cannot cross the blood-brain barrier. However, if the blood-brain barrier is impaired, the drug reaches the brain and can cause serious side effects there. In reciprocal action with other drugs, however, loperamide can cross the blood-brain barrier more easily.
If ketoconazole, verapamil and quinidine are taken at the same time, loperamide can cause breathing disorders. Interactions can also occur with ritonavir, an HIV proteinase inhibitor. It should also be noted that loperamide functionally inhibits acid sphingomyelinase (FIASMA). The resulting dysregulation can lead to serious clinical symptoms.
