Loperamide: A Readily Available but Dangerous Opioid Substitute

Loperamide-Induced Torsades de Pointes

Loperamide is a readily available, over-the-counter medication used to treat diarrhea. At therapeutic doses, loperamide exerts its effects mainly on the intestinal opioid receptors with minimal psychoactive effects; however, at supratherapeutic doses, it reaches central opioid receptors. With tighter regulations on opioid prescriptions, loperamide has emerged as a popular drug of abuse among opioid users. At supratherapeutic doses, loperamide can cause severe cardiac toxicity, resulting in wide QRS rhythms, severe bradycardia, prolonged QTc, polymorphic ventricular tachycardia, and cardiac arrest. We present the case of a 27-year-old female with a history of heroin abuse who suffered torsades de pointes resulting in cardiac arrest in the setting of a loperamide overdose.

Electroacupuncture Improves Intestinal Motility through Exosomal miR-34c-5p Targeting SCF/c-Kit Signaling Pathway in Slow Transit Constipation Model Rats

Background. The pathogenesis of slow transit constipation (STC) is associated with exosomal miR-34c-5p. Electroacupuncture (EA) improves gastrointestinal motility in gastrointestinal disorders, especially STC. Our study aimed to explore the mechanism by which EA improves intestinal motility by modulating the release of exosomes and the transmission of exosomal miR-34c-5p. Methods. Fifty rats were randomly divided into five groups. STC model rats were induced, and GW4869, the exosome release inhibitor, was used to inhibit the release of exosome. The serum exosomes were authenticated under a transmission electron microscope and nanoparticle tracking analysis. RT-qPCR detected the expression of miR-34c-5p in serum exosomes and colonic tissues. The fecal number in 24 hours, Bristol scores, and intestinal transit rates were used to assess intestinal motility. Subsequently, hematoxylin and eosin (H&E) staining was used to examine the colonic mucosal histology. Finally, the expression of stem cell factor (SCF) and receptor tyrosine kinase (c-Kit) protein was measured using immunohistochemistry staining. Results. We found that EA upregulated exosomal miR-34c-5p in serum and downregulated miR-34c-5p in colonic tissues ( $P<0.01$ ). EA improved fecal numbers in 24 hours, Bristol scores, and intestinal transit rates in STC rats ( $P<0.01$ ). EA recovered the colonic histological structure and enhanced the expression of SCF and c-Kit protein ( $P<0.01$ ). The therapeutic effect of EA was attenuated after inhibiting the release of the exosome. Conclusion. Our results indicated that EA improves intestinal motility in STC rats by transporting of exosomal miR-34c-5p targeting the SCF/c-Kit signaling pathway.

Case Report: Opioid Use Disorder Associated With Low/Moderate Dose of Loperamide in an Intellectual Disability Patient With CYP3A and P-Glycoprotein Reduced Activity

Loperamide is an over-the-counter antidiarrheal for which increasing cases of abuse or misuse are described. We report the onset of opioid use disorder associated with low to moderate doses of loperamide in an intellectual disability patient without previous history of substance use disorder (SUD). Our patient presented strongly reduced activities of CYP3A and P-glycoprotein, which are mainly involved in loperamide metabolism and transport. We suggest that this led to an increase in bioavailability, systemic exposure, and brain penetration thus allowing loperamide to act on the central nervous system and contributing to the development of SUD. Slow release oral morphine (SROM) was chosen as opioid agonist treatment, which successfully contained loperamide use and globally improved her clinical condition. This situation highlights the need for caution and awareness when prescribing loperamide, particularly in vulnerable patients with few cognitive resources to understand the risks of self-medication and little insight into its effects.

DARK Classics in Chemical Neuroscience: Loperamide

Loperamide, a popular and inexpensive over-the-counter antidiarrheal medicine, is a potent μ-opioid receptor agonist approved by the U.S. Food and Drug Administration (FDA). It has been on the market since 1976 and is relatively safe with no central nervous system-related side effects when used for a short period of time at the recommended therapeutic dose (2-8 mg/day). In recent years, loperamide has become notoriously known as the "poor man's methadone" for people with substance dependence due to the increase in loperamide overdoses from self-administered medication to treat opioid withdrawal symptoms. As a result, in 2018, the FDA decided to limit the available packaged dose of loperamide to stop prominent abuse. This review provides the synthesis and chemical properties of loperamide as well as the pharmacology and adverse effects of its use and the social effects of such abuse.

Discovery and Characterization of the Biflavones From Ginkgo biloba as Highly Specific and Potent Inhibitors Against Human Carboxylesterase 2

Human carboxylesterase 2 (CES2), one of the most abundant hydrolases distributed in the small intestine, has been validated as a key therapeutic target to ameliorate the intestinal toxicity caused by irinotecan. This study aims to discover efficacious CES2 inhibitors from natural products and to characterize the inhibition potentials and inhibitory mechanisms of the newly identified CES2 inhibitors. Following high-throughput screening and evaluation of the inhibition potency of more than 100 natural products against CES2, it was found that the biflavones isolated from Ginkgo biloba displayed extremely potent CES2 inhibition activities and high specificity over CES1 (>1000-fold). Further investigation showed that ginkgetin, bilobetin, sciadopitysin and isoginkgetin potently inhibited CES2-catalyzed hydrolysis of various substrates, including the CES2 substrate-drug irinotecan. Notably, the inhibition potentials of four biflavones against CES2 were more potent than that of loperamide, a marketed anti-diarrhea agent used for alleviating irinotecan-induced intestinal toxicity. Inhibition kinetic analyses demonstrated that ginkgetin, bilobetin, sciadopitysin and isoginkgetin potently inhibited CES2-catalyzed fluorescein diacetate hydrolysis via a reversible and mixed inhibition manner, with K _i values of less than 100 nM. Ensemble docking and molecular dynamics revealed that these biflavones could tightly and stably bind on the catalytic cavity of CES2 via hydrogen bonding and π-π stacking interactions, while the interactions with CES1 were awfully poor. Collectively, this study reports that the biflavones isolated from Ginkgo biloba are potent and highly specific CES2 inhibitors, which offers several promising lead compounds for developing novel anti-diarrhea agent to alleviate irinotecan-induced diarrhea.

Opioid Management: Initiating, Monitoring, and Tapering

Numerous guidelines targeting safe use of opioids for chronic pain have been published but substantial challenges persist in clinical application of best practice recommendations. This article describes a pragmatic approach to clinical care of adults with chronic pain receiving long-term opioid therapy. Three components of care are emphasized: (1) medical and mental health assessment before initiating opioid therapy, (2) clinical surveillance during the course of long-term opioid therapy, and (3) clinical considerations and strategies governing opioid tapering. A pressing need exists for ongoing research to further clarify the optimal role that long-term opioid therapy has in treatment of chronic pain.