Loperamide bloody diarrhea. In 1990, all formulations for children of the antidiarrheal loperamide were banned in Pakistan. Loperamide is not recommended in the UK for use during pregnancy or by nursing mothers. In the US, loperamide is classified by the FDA as pregnancy category C. Studies in rat models have shown no teratogenicity, but sufficient studies in humans have not been conducted. One controlled, prospective study of 89 women exposed to loperamide during their first trimester of pregnancy showed no increased risk of malformations. This, however, was only one study with a small sample size. Loperamide can be present in breast
Loperamide first-pass metabolism by the liver. Loperamide metabolizes into an MPTP-like compound, but is unlikely to exert neurotoxicity. Efflux by P-glycoprotein also prevents circulating loperamide from effectively crossing the blood–brain barrier, so it can generally only antagonize muscarinic receptors in the peripheral nervous system, and currently has a score of 1 on the anticholinergic cognitive burden scale. Concurrent administration of P-glycoprotein inhibitors such as quinidine potentially allows loperamide to cross the blood–brain barrier and produce central morphine-like effects. Loperamide taken with quinidine was found to produce respiratory depression, indicative of central opioid action. Loperamide has been shown to cause a mild