Loperamide have negative effects from rebound constipation. If a suspicion exists of diarrhea associated with organisms that can penetrate the intestinal walls, such as or "Salmonella", loperamide is contraindicated as a primary treatment. Loperamide treatment is not used in symptomatic "C. difficile" infections, as it increases the risk of toxin retention and precipitation of toxic megacolon. Loperamide should be administered with caution to people with liver failure due to reduced first-pass metabolism. Additionally, caution should be used when treating people with advanced HIV, as cases of both viral and bacterial toxic megacolon have been reported. If abdominal distension is noted, therapy
Loperamide milk, and is not recommended for breast-feeding mothers. Loperamide is a substrate of P-glycoprotein; therefore, the concentration of loperamide will increase when given with a P-glycoprotein inhibitor. Common P-glycoprotein inhibitors include quinidine, ritonavir, and ketoconazole, among others. Loperamide is capable of decreasing the absorption of some other drugs. As an example, saquinavir concentrations can decrease by half when given with loperamide. Loperamide is an antidiarrheal agent which decreases intestinal movement. As such, when combined with other antimotility drugs, the risk of constipation is increased. These drugs include other opioids, antihistamines, antipsychotics, and anticholinergics. Loperamide is an opioid-receptor agonist and acts