The Potential Mechanisms behind Loperamide-Induced Cardiac Arrhythmias Associated with Human Abuse and Extreme Overdose

Loperamide has been a safe and effective treatment for diarrhea for many years. However, many cases of cardiotoxicity with intentional abuse of loperamide ingestion have recently been reported. We evaluated loperamide in in vitro and in vivo cardiac safety models to understand the mechanisms for this cardiotoxicity. Loperamide slowed conduction (QRS-duration) starting at 0.3 µM [~1200-fold (×) its human Free Therapeutic Plasma Concentration; FTPC] and reduced the QT-interval and caused cardiac arrhythmias starting at 3 µM (~12,000× FTPC) in an isolated rabbit ventricular-wedge model. Loperamide also slowed conduction and elicited Type II/III A-V block in anesthetized guinea pigs at overdose exposures of 879× and 3802× FTPC. In ion-channel studies, loperamide inhibited hERG (IKr), INa, and ICa currents with IC50 values of 0.390 µM, 0.526 µM, and 4.091 µM, respectively (i.e., >1560× FTPC). Additionally, in silico trials in human ventricular action potential models based on these IC50s confirmed that loperamide has large safety margins at therapeutic exposures (≤600× FTPC) and confirmed repolarization abnormalities in the case of extreme doses of loperamide. The studies confirmed the large safety margin for the therapeutic use of loperamide but revealed that at the extreme exposure levels observed in human overdose, loperamide can cause a combination of conduction slowing and alterations in repolarization time, resulting in cardiac proarrhythmia. Loperamide's inhibition of the INa channel and hERG-mediated IKr are the most likely basis for this cardiac electrophysiological toxicity at overdose exposures. The cardiac toxic effects of loperamide at the overdoses could be aggravated by co-medication with other drug(s) causing ion channel inhibition.

Effects of opioid receptor agonist and antagonist medications on electrocardiogram changes and presentation of cardiac arrhythmia: review article

BACKGROUND/PURPOSE

Mortality associated with prescription opioids has significantly increased over the past few decades and is considered a global pandemic. Prescribed opioids can cause cardiac arrhythmias, leading to fatal outcomes and unexpected death, even in the absence of structural cardiac disease. Despite the extent of cardiac toxicity and death associated with these medications, there is limited data to suggest their influences on cardiac electrophysiology and arrhythmias, with the exception of methadone. The goal of our review is to describe the possible mechanisms and to review the different ECG changes and arrhythmias that have been reported.

METHODS

A literature search was performed using Google Scholar, PubMed, Springer, Ovid, and Science Direct to identify studies that demonstrated the use of prescription opioids leading to electrocardiogram (ECG) changes and cardiac arrhythmias.

RESULTS

Many of the commonly prescribed opioid medications can uniquely effect the ECG, and can lead to the development of various cardiac arrhythmias. One of the most significant side effects of these drugs is QTc interval prolongation, especially when administered to patients with a baseline risk for QTc prolongation. A prolonged QTc interval can cause lethal torsades de pointes and ventricular fibrillation. Obtaining an ECG at baseline, following a dosage increase, or after switching an opioid medication, is appropriate in patients taking certain prescribed opioids. Opioids are often used first line for the treatment of acute and chronic pain, procedural sedation, medication opioid use disorders, and maintenance therapy.

CONCLUSIONS

To reduce the risk of cardiac arrhythmias and to improve patient outcomes, consideration of accurate patient selection, concomitant medications, electrolyte monitoring, and vigilant ECG monitoring should be considered.

Efficacy of acupuncture in refractory irritable bowel syndrome: study protocol for a randomised controlled trial

INTRODUCTION

Irritable bowel syndrome (IBS) is a common chronic functional gastrointestinal disorder that presents with abdominal pain/discomfort and altered bowel patterns. IBS has multiple potential causes for which conventional medicines have had limited success, resulting in a significant number of patients who do not sensitively respond to pharmacotherapy for a period of 12 months and who develop a continuing symptom profile (described as refractory IBS) and seek help through (non)pharmacological treatments. The aim of this study is to investigate the efficacy and safety of acupuncture therapy for refractory IBS on the basis of conventional treatments.

METHODS AND ANALYSIS

A total of 170 eligible patients who meet the Rome IV criteria for refractory IBS will be randomly allocated to receive acupuncture or sham acupuncture. Each patient will receive 12 sessions of acupuncture over 4 weeks and a 4-week follow-up. The primary outcome will be the IBS Symptom Severity Score. Secondary outcomes will include the proportion of participants experiencing adequate relief of global IBS symptoms, the weekly frequency of defecation, the stool properties assessed by the Bristol Grading Scale, the Work and Social Adjustment Scale, the IBS-Quality of Life score, and the Self-Rating Depression Scale and Self-Rating Anxiety Scale anxiety and depression scores. Outcome measures will be collected at baseline, 2 and 4 weeks of the intervention, and 6 and 8 weeks after the intervention. Categorical variables will be compared with Fisher's exact test or the Wilcoxon rank-sum test, and continuous variables will be compared using Student's t-test or the Wilcoxon rank-sum test.

ETHICS AND DISSEMINATION

The entire project has been approved by the ethics committees of Beijing University of Chinese Medicine (2020BZYLL0507) and Sichuan Province Regional Institution for Conducting Research on Traditional Chinese Medicine (2020KL-025). The outcomes of the trial will be disseminated through peer-reviewed publications.

TRIAL REGISTRATION NUMBER

NCT04276961.

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.

Loperamide Abuse and Its Sequelae

INTRODUCTION

Loperamide is an opioid available over the counter and in prescription form. Loperamide functions as a μ-agonist within the enteric nervous system to slow intestinal motility. Its antidiarrheal properties and primarily peripheral activity make loperamide an important tool in the management of inflammatory bowel disease.

CASE REPORT

A 42-year-old man was found unconscious in cardiac arrest, and emergency medical personnel restored normal sinus rhythm. Family reported complaints of abdominal pain and that he "went through a lot" of loperamide. In the emergency department, the patient exhibited symptoms consistent with an opioid overdose. Mental status improved after administration of naloxone, an opioid antagonist. An electrocardiogram revealed a prolonged QTc interval, which progressed into Torsades de Pointes rhythm during admission. The patient succumbed from hypoxic brain injury, and there was evidence of acute pancreatitis at autopsy. Loperamide and desmethylloperamide (loperamide metabolite) were detected in blood samples. Cause of death was ruled loperamide toxicity.

DISCUSSION

Because of reduced central nervous system activity and associated euphoria at therapeutic doses, loperamide abuse is rarely reported. This case demonstrates that an overdose on loperamide can occur in patients seeking symptom alleviation, and may mimic the presentation of opioid overdose.

Randomised, double-blind, placebo controlled multi-centre study to assess the efficacy, tolerability and safety of Enterosgel® in the treatment of irritable bowel syndrome with diarrhoea (IBS-D) in adults

BACKGROUND

Irritable bowel syndrome (IBS) with diarrhoea (IBS-D) is a common and chronic condition that can significantly impair quality of life. The emergence of new drugs for IBS-D has been slow and there is a need for new treatments, including drug-free treatments, which are easy to use and suitable for different patient groups. Currently available drug-free treatments include Enterosgel®, an intestinal adsorbent approved for use in IBS-D and acute diarrhoea and available over-the-counter in the UK and 30 countries worldwide. The aim of this randomised, double-blind, placebo-controlled, multi-centre study is to test the efficacy and safety of Enterosgel® compared to placebo in symptomatic treatment in IBS-D.

METHODS/DESIGN

We will recruit 430 participants with IBS-D from approximately 30 primary and secondary care sites in England. Participants meeting the required abdominal pain and stool consistency criteria over a 2-week screening period will be randomly allocated to receive blinded treatment (Enterosgel® or placebo) for 8 weeks. This will be followed by an 8-week open-label treatment phase with Enterosgel®. Participants will be allowed to adjust their daily dosage during both phases based on their symptoms. Participants will then return to standard care and those who responded to treatment will receive a follow-up call 8 weeks later. Co-medication with loperamide will be permitted and use recorded. The primary outcome measure is the percentage of participants defined as responders for abdominal pain and stool consistency during at least 4 weeks in the 8-week blinded phase. Secondary outcome measures include stool frequency, stool consistency, abdominal pain, bloating, urgency, adequate relief, questionnaire scores and rescue medication use. Exploratory outcomes will be assessed in subsets of participants including qualitative and quantitative data on faecal microorganisms and biomarkers and gut-related measurements from magnetic resonance imaging data.

DISCUSSION

This is the first large scale randomised controlled trial investigating Enterosgel® in IBS-D. A study design with blinded phase followed by an open-label phase was chosen to encourage participation and study completion. Demonstrating that Enterosgel® is effective and safe in IBS-D could encourage adoption by patients and healthcare professionals and foster future clinical trials assessing its use in related conditions.

TRIAL REGISTRATION

ISRCTN17149988. Prospectively registered on 14 November 2017.

Left Ventricular Regional Wall Motion Abnormality in the Setting of Acute Loperamide Overdose

Loperamide is an inexpensive, over-the-counter antidiarrheal agent with emerging reports of overdose due to its opioid properties. Although it is considered by many patients to be safe, cardiotoxicity has been reported, prompting the United States Food and Drug Administration to release a warning regarding the arrhythmogenic potential of loperamide. We present a case of a 32-year-old male presenting in acute loperamide overdose and subsequent cardiac dysrhythmia with focal wall motion abnormalities on echocardiogram. This finding has not been previously reported in the literature and is unique in this clinical presentation. We also highlight the potential mechanisms for loperamide cardiotoxicity and its challenging management.

Loperamide cardiotoxicity: "A Brief Review"

Loperamide is a popular antidiarrheal medication that has been used for many years. It is currently gaining more attention among healthcare professionals due to its increasing potential for side effects. At present, it is considered safe enough to be sold over the counter. In contrast with other opioid agonists, loperamide is a peripherally acting μ-receptor agonist exerting its effects mainly on the myenteric plexus of the gastrointestinal longitudinal muscle layer. It decreases peristalsis and fluid secretion resulting in longer gastrointestinal transit time. The bioavailability of the drug is extremely low. Moreover, it is actively excluded from the central nervous system; hence, it lacks the central effects of euphoria and analgesia at the recommended dosages. Loperamide abuse has been steadily increasing in the United States. Abusers typically ingest high doses in desire to achieve a satisfactory central nervous system drug penetration. This has made it a potential over the counter substitute for self-treating opioid withdrawal symptoms and achieving euphoric effects.

Loperamide and cardiac events: Is high-dose use still safe for chemotherapy-induced diarrhea?

High-dose loperamide is often used for the acute management of chemotherapy-induced diarrhea, with a maximum daily dosing of up to 24 mg. Recently, the US Food and Drug Administration has issued a warning that loperamide can cause rare serious cardiac events, including QT prolongation, torsades de pointes, cardiac arrest and death. Most events were reported in patients taking very high doses for an extended period of time. Daily intake ranged from 64 mg to 1600 mg, often continuously for weeks or months. In addition, the reported serum levels of loperamide ranged from 22 ng/mL to 210 ng/mL, which is likely significantly higher than that expected from patients taking the recommended doses for chemotherapy-induced diarrhea. Overall, the incidence of serious cardiac events associated with loperamide remains low. In balance, the risk of uncontrolled complications from chemotherapy-induced diarrhea is likely greater than the rare cardiac risk associated with the chronic misuse of much higher doses of loperamide.

Clinical Review: Loperamide Toxicity

Loperamide is a nonprescription opioid widely used for the treatment of diarrhea. Although it is relatively safe at therapeutic doses, increasing reports describe its misuse and abuse at very high doses either for euphoric effects or to attenuate symptoms of opioid withdrawal. Life-threatening loperamide toxicity can result from the relatively new clinical syndrome of loperamide-induced cardiac toxicity. These patients are often young and may present in cardiac arrest or with unheralded, recurrent syncope in conjunction with ECG abnormalities, including marked QT-interval prolongation, QRS-interval widening, and ventricular dysrhythmias. Features of conventional opioid toxicity may also be present. The mainstays of treatment include advanced cardiac life support and supportive care, although selected patients may be candidates for overdrive pacing, intravenous lipid emulsion, or extracorporeal membrane oxygenation. In patients who survive loperamide toxicity, consideration should be given to the treatment of an underlying opioid use disorder, if present.

Intentional Misuse and Abuse of Loperamide: A New Look at a Drug with "Low Abuse Potential"

BACKGROUND

Despite its opioid properties, loperamide has long been thought to have low abuse potential due to its poor absorption from the gastrointestinal tract and limited potential to cross the blood-brain barrier. A recent patient reportedly taking loperamide to avoid heroin withdrawal symptoms, at doses approximately 100 times those recommended, directed our attention to this issue.

OBJECTIVES

1) Investigate number of cases of intentional loperamide abuse and misuse reported to poison centers between 2009 and 2015; 2) Compile reports of clinical effects of loperamide abuse; and 3) Search for evidence of increasing Internet interest in the central opioid effects of loperamide.

METHODS

For the years 2009 thru 2015, we reviewed exposure calls related to misuse/abuse of loperamide in the Texas Poison Center Network's database and the National Poison Data System. We used Google trend analysis to detect evidence of increased Internet interest in the illicit use of loperamide.

RESULTS

Between 2009 and 2015, the number of misuse/abuse calls related to loperamide alone nearly doubled, with about one-third of cases occurring in teens and young adults in their 20s. Of particular concern are reports of significant cardiotoxic effects (∼18% of cases), including conduction defects and various dysrhythmias, sometimes leading to death. Google Trends analysis demonstrates an increasing number of searches for "loperamide high" and "loperamide withdrawal" beginning in 2011.

CONCLUSIONS

Loperamide misuse/abuse seems to be on the rise. Given its propensity to induce conduction disturbances and dysrhythmias at very high doses, emergency physicians should be vigilant for this form of drug abuse.

Adverse event detection using the FDA post-marketing drug safety surveillance system: Cardiotoxicity associated with loperamide abuse and misuse

OBJECTIVE

The purpose of this investigation was to identify and characterize post-marketing reports of cardiotoxicity, including torsades de pointes (TdP), associated with loperamide use.

METHODS

We searched the U.S. Food and Drug Administration Adverse Event Reporting System (FAERS) database for post-marketing reports of serious cardiac adverse events associated with loperamide use from December 28, 1976 (U.S. drug approval date), through December 14, 2015. We also conducted a Pubmed and Google Scholar search to identify additional published reports of cardiotoxicity associated with loperamide in the medical literature through February 11, 2016.

RESULTS

Forty-eight cases of serious cardiac adverse events associated with loperamide use composed the case series. The most frequently reported cardiac adverse events were syncope (n = 24), cardiac arrest (n = 13), QT-interval prolongation (n = 13), ventricular tachycardia (n = 10), and TdP (n = 7). There were 10 cases that resulted in death. Of the 48 cases, the most commonly reported reasons for use can be characterized as drug abuse (n = 22) and diarrhea treatment (n = 17). More than one-half of the 48 cases were reported after 2010. Of the 22 drug abuse cases, the median daily dose was 250 mg (range 70 mg to 1600 mg) and events occurred as early as 6 hours after a dose and as long as 18 months after initiation of loperamide. Thirteen of the 22 cases reported using loperamide for euphoric or analgesic effects, and 9 reported use to prevent opioid withdrawal symptoms.

CONCLUSION

The FAERS case reports provide evidence to suggest that high doses of loperamide are associated with TdP and other serious cardiac adverse events. The majority of cases in this series occurred in the setting of drug abuse for the purpose of preventing opioid withdrawal or to produce euphoric effects. It is important for both clinicians and patients to be aware of this potential risk, because prompt therapy and discontinuation of the offending agent are often essential to management and prevention of loperamide-induced cardiac arrhythmias.

Loperamide Induced Life Threatening Ventricular Arrhythmia

Loperamide is over-the-counter antidiarrheal agent acting on peripherally located μ opioid receptors. It is gaining popularity among drug abusers as opioid substitute. We report a case of a 46-year-old male that was presented after cardiac arrest. After ruling out ischemia, cardiomyopathy, pulmonary embolism, central nervous system pathology, sepsis, and other drug toxicity, we found out that patient was using around 100 mg of Loperamide to control his chronic diarrhea presumably because of irritable bowel syndrome for last five years and consumed up to 200 mg of Loperamide daily for last two days before the cardiac arrest. We hypothesize that the patient's QTc prolongation and subsequent cardiac arrest are due to Loperamide toxicity. Patient experienced gradual resolution of tachyarrhythmia and gradual decrease in QTc interval during hospitalization which supports the evidence of causal relationship between Loperamide overdose and potentially fatal arrhythmias. It also provided the clue that patient may have congenital long QT syndrome which was unmasked by Loperamide causing ventricular arrhythmias. This case adds one more pearl in the literature to support that Loperamide overdose related cardiac toxicity does exist and it raises concerns over Loperamide abuse in the community.

Systematic review of loperamide: No proof of antibiotics being superior to loperamide in treatment of mild/moderate travellers' diarrhoea

Looking at the worldwide emergency of antimicrobial resistance, international travellers appear to have a central role in spreading the bacteria across the globe. Travellers' diarrhoea (TD) is the most common disease encountered by visitors to the (sub)tropics. Both TD and its treatment with antibiotics have proved significant independent risk factors of colonization by resistant intestinal bacteria while travelling. Travellers should therefore be given preventive advice regarding TD and cautioned about taking antibiotics: mild or moderate TD does not require antibiotics. Logical alternatives are medications with effects on gastrointestinal function, such as loperamide. The present review explores literature on loperamide in treating TD. Adhering to manufacturer's dosage recommendations, loperamide offers a safe and effective alternative for relieving mild and moderate symptoms. Moreover, loperamide taken singly does no predispose to contracting MDR bacteria. Most importantly, we found no proof that would show antibiotics to be significantly more effective than loperamide in treating mild/moderate TD.