Antimotility agent
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Antimotility agents are drugs used to alleviate the symptoms of diarrhea. These include loperamide (Imodium), bismuth subsalicylate (Pepto-Bismol),[1] diphenoxylate with atropine (Lomotil), and opiates such as paregoric, tincture of opium, codeine, and morphine. In diarrhea caused by invasive pathogens such as Salmonella, Shigella, and Campylobacter, the use of such agents has generally been strongly discouraged, though evidence is lacking that they are harmful when administered in combination with antibiotics in Clostridioides difficile cases.[2] Use of antimotility agents in children and the elderly has also been discouraged in treatment of EHEC (Shiga-like toxin producing Escherichia coli) due to an increased rate of hemolytic uremic syndrome.[3]
Mechanism of action
Loperamide is a μ-opioid receptor agonist.[4] By binding to μ-opioid receptors, loperamide inhibits acetylcholine release and decreases excitation of neurons in the myenteric plexus, which leads to a decrease in peristalsis.[4] Decreasing intestinal motility prolongs the transit time of food content through the digestive tract, which allows for more fluid absorption; thereby alleviating diarrhea symptoms and improving stool consistency and frequency.[4]
Unlike other opiates, loperamide does not cross the blood brain barrier, so there is minimal risk for abuse.[5]
Adverse effects
Side effects of use of anti-motility agents include:
- Constipation[4]
- Abdominal cramps and discomfort[4]
- Nausea[4]
- Drowsiness[6]
- Dizziness[6]
- Dry mouth[6]
- Skin rash[6]
Contraindications
Contraindications include:
- Severe liver damage[7]
- Children 2 years old or younger[8]
- Malnourished individuals[6]
- Dehydrated individuals[6]
- Bloody diarrhea present[6]
Drug interactions
CYP3A4 inhibitors, such as erythromycin, fluconazole, ketoconazole, quinidine, and ritonavir, increase plasma levels of loperamide.[7]