Treatment of cholestatic pruritus in children

Treatment of Cholestasis in Infants and Young Children

PURPOSE OF REVIEW

Cholestasis is characterized by a conjugated hyperbilirubinemia secondary to impaired bile synthesis, transport, or excretion from the liver. It is always pathologic and can be indicative of an underlying hepatobiliary, genetic, or metabolic disorder, several of which require timely diagnosis to ensure proper management and optimal outcomes. This review provides an overview of the evaluation of cholestasis with a focus on current and emerging treatment strategies.

RECENT FINDINGS

Increased accessibility of next generation sequencing (NGS) allows for utilization of genetic testing early in the diagnostic process. This may alter the clinical algorithm for diagnosis of cholestatic disorders. An enhanced understanding of the underlying pathophysiology may help guide future development of targeted therapies, such as ileal bile acid transporter (IBAT) inhibitors. These were recently approved for treatment of cholestatic pruritus in patients with Alagille syndrome and Progressive Familial Intrahepatic Cholestasis. Current management of cholestasis is aimed at the biochemical consequences of impaired bile flow, including malnutrition, pruritus, and progressive fibrosis. NGS has led to an enhanced understanding of biliary pathology and may guide development of future treatment modalities based on specific gene mutations. Rapid discernment of the underlying etiology is essential as new treatment modalities emerge.

Cholestatic Pruritus in Children: Conventional Therapies and Beyond

Pruritus in the setting of cholestatic liver disease is difficult to treat and occurs in patients ranging in age from infancy to adulthood. Likely multifactorial in etiology, this symptom often involves multimodal therapy targeting several pathways and mechanisms proposed in the underlying etiology of cholestatic pruritus. Many patients in both the pediatric and adult populations continue to experience unrelenting pruritus despite maximal conventional therapy. Options are further limited in treating pediatric patients due to sparse data regarding medication safety and efficacy in younger patients. Conventional therapies for the treatment of cholestatic pruritus in children include ursodeoxycholic acid, cholestyramine, hydroxyzine, and rifampin. Certain therapies are more routinely used in the adult populations but with limited data available for use in child and adolescent patients, including opioid antagonists and selective serotonin reuptake inhibitors. Recently, ileal bile acid transport inhibitors have been shown to alleviate pruritus in many children with Alagille syndrome and progressive familial intrahepatic cholestasis and is an additional therapy available for consideration for these patients. Ultimately, surgical options such as biliary diversion or liver transplantation are considered in specific circumstances when medical therapies have been exhausted and pruritus remains debilitating. While further investigation regarding underlying etiologies and effective therapies are needed to better understand itch pathogenesis and treatment in pediatric cholestasis, current considerations beyond conventional management include the use of opioid antagonists, selective serotonin reuptake inhibitors, ileal bile acid transport inhibitors, and surgical intervention.

Mechanism of TGF-β1 inhibiting Kupffer cell immune responses in cholestatic cirrhosis

Effect of exogenous transforming growth factor-β1 (TGF-β1) on cholestatic mice by inhibiting Kupffer cell immune responses in liver was investigated. To induce cholestasis, BALB/c mice received a sham operation (Mock group), or underwent a bile duct ligation (BDL group) and then were subcutaneously injected with TGF-β1 at multiple sites (TGF group). Liver functions were evaluated according to the levels of alanine aminotransferase (ALT), aspartate aminotransferase AST and γ-glutamyltranspeptidase (γ-GT) in serum samples. Expression of nuclear factor-κB (NF-κB), interleukin-6 (IL-6), IL-1β and tumor necrosis factor-α (TNF-α) was detected. Expression of inducible nitric oxide synthase (iNOS) and arginase-1 (Arg-1) in Kupffer cells (KCs) of the liver was detected. The isolated KCs were divided into control group, LPS group, TGF group and Galunisertib group and western blot analysis was used to detect the expression of NF-κB, IL-6, IL-1β, TNF-α, iNOS and Arg-1. The percentage of CD40, CD86, CD204 and CD206 as macrophage cell surface antigens were measured by flow cytometry. The indexes of liver function and liver fibrosis of the mice in the TGF group were significantly lower than those in the BDL group (P<0.05). The levels of IL-1β, IL-6 and TNF-α in the liver were lower than those in the BDL group, while the level of IL-10 was significantly increased (P<0.05). M2-type transformation occurred in liver Kupffer cells of mice in the TGF group. In cell experiments, TGF treatment downregulated the expression of IL-1β, IL-6, TNF-α and NF-κB, increased the expression of IL-10, and induced M2-type transformation in macrophages (P<0.05). In conclusion, TGF-ß1 diminished the progression of cholestasis in mice by inhibiting the inflammatory response of KCs and regulating KC polarization.

Cholestasis in the Baby and Infant

Cholestasis in children is a serious condition due to various aetiologic factors. If children with jaundice present with acholic stool, dark urine colour, or direct hyperbilirubinaemia, the patient should be evaluated urgently. Early and timely diagnosis and initiation of appropriate treatment are extremely important determinants of morbidity and mortality. In the neonatal period, idiopathic neonatal cholestasis, alpha-1 antitrypsin deficiency, cholestasis from infections, and biliary atresia are the most common causes of cholestasis. Nowadays, with the development of genetic and molecular biological studies, the diagnosis of many diseases that have previously been evaluated as ‘idiopathic‘ can be made. It is the aetiological factor that determines the prognosis. The treatment plan is created in accordance with aetiological causes and in response to symptoms such as pruritus and malabsorption: this can be surgical treatment across a diverse spectrum, from biliary diversion to liver transplantation. In this study, the aetiology, diagnosis, and treatment of cholestasis in babies and infants are reviewed in the light of current literature.

Progressive familial intrahepatic cholestasis: diagnosis, management, and treatment

Progressive familial intrahepatic cholestasis (PFIC) is a group of autosomal recessive cholestatic liver diseases which are subgrouped according to the genetic defect, clinical presentation, laboratory findings and liver histology. Progressive liver fibrosis, cirrhosis, and end stage liver disease (ESLD) may eventually develop. PFIC was first described in Amish descendants of Jacob Byler, therefore it was originally called Byler disease. But it can be seen anywhere on the globe. This review summarizes the main features of the subtypes of the disease and discusses the current available diagnosis, conservative and surgical therapeutic options.

Management options for cholestatic liver disease in children

Due to a peculiar age-dependent increased susceptibility, neonatal cholestasis affects the liver of approximately 1 in every 2500 term infants. A high index of suspicion is the key to an early diagnosis, and to implement timely, often life-saving treatments. Even when specific treatment is not available or curative, prompt medical management and optimization of nutrition are of paramount importance to survival and avoidance of complications. Areas covered: The present article will prominently focus on a series of newer diagnostic and therapeutic options of cholestasis in neonates and infants blended with consolidated established paradigms. The overview of strategies for the management reported here is based on a systematic literature search published in English using accessible databases (PubMed, MEDLINE) with the keywords biliary atresia, choleretics and neonatal cholestasis. References lists from retrieved articles were also reviewed. Expert commentary: A large number of uncommon and rare hepatobiliary disorders may present with cholestasis during the neonatal and infantile period. Potentially life-saving disease-specific pharmacological and surgical therapeutic approaches are currently available. Advances in hepatobiliary transport mechanisms have started clarifying fundamental aspects of inherited and acquired cholestasis, laying the foundation for the development of possibly more effective specific therapies.

Serum Autotaxin Activity Correlates With Pruritus in Pediatric Cholestatic Disorders

OBJECTIVE

Pruritus is a common symptom of cholestatic liver disorders. The present study aimed at evaluating autotaxin (ATX), a lysophospholipase recently identified as potential cause for cholestatic pruritus, in pediatric cholestatic diseases presenting with or without itching.

METHODS

A cohort of 45 children consisting of 14 patients experiencing itching (Alagille syndrome [n = 10], complete extrahepatic biliary atresia [n = 2], neonatal sclerosing cholangitis (n = 1), progressive familial intrahepatic cholestasis type 2 [n = 1]), 9 patients with bile acid synthesis defects (3β-hydroxy-C27-steroid-oxidoreductase [n = 7] and Δ-3-oxosteroid-5β-reductase deficiency [n = 2]), and 22 healthy children were studied. Serum ATX activity and total serum bile salt were determined enzymatically, ATX protein content was semiquantified by Western blotting. Using real-time polymerase chain reaction, ATX mRNA expression was studied in HepG2 cells treated with farnesoid-X-receptor agonists or vehicle.

RESULTS

Serum ATX activity was increased in pruritic children with Alagille and other cholestatic syndromes (mean ± standard deviation: 16.1 ± 4.3 nmol · mL · min) compared with children with nonpruritic cholestatic diseases with bile acid synthesis defects (10.4 ± 4.7 nmol · mL · min; P < 0.01) and healthy controls (7.6 ± 2.3 nmol · mL · min; P < 0.001). ATX protein levels closely correlated with serum ATX activity. Serum ATX activity and total serum bile salt showed a linear correlation with itch intensity (r = 0.66, P < 0.001 and r = 0.80, P < 0.001, respectively). No correlation was observed between ATX activity and bilirubin. ATX mRNA expression in HepG2 cells was not induced by farnesoid-X-receptor ligands.

CONCLUSIONS

Serum ATX activity correlated with itch intensity in children with cholestatic diseases. Bile salts did not increase ATX expression in vitro. ATX inhibitors may be useful antipruritic agents in pediatric cholestatic disorders.

Different techniques for biliary diversion in progressive familial intrahepatic cholestasis

BACKGROUND

Progressive familial intrahepatic cholestasis (PFIC) is a cholestatic liver disease of childhood. Pruritus resulting from increased bile salts in serum might not respond to medical treatment, and internal or external biliary drainage methods have been described. In this study, we aimed to evaluate different internal drainage techniques in patients with PFIC.

PATIENTS AND METHODS

Between 2009 and 2014, seven children (4 male, 3 female, 3months-5years old), (median 2years of age) with PFIC were evaluated. The patients were reviewed according to age, gender, complaints, surgical technique, laboratory findings and outcome. In each two patients, cholecystoileocolonic anastomosis, cholecystojejunocolonic anastomosis and cholecystocolostomy were performed. Cholecysto-appendico-colonic anastomosis was the technique used in one patient.

RESULTS

Jaundice and excessive pruritus were the main complaints. One of the patients with cholecystoileocolonic anastomosis died of comorbid pathologies (cirrhosis, adhesive obstruction and severe sepsis). Temporary rectal bleeding was observed in all the patients postoperatively. Regardless of the surgical technique, pruritus was dramatically decreased in all the patients in the postoperative period.

CONCLUSION

Regardless of the technique, internal biliary diversion methods are beneficial for the relief of pruritus in PFIC patients. Selection of the surgical method might vary depending on the surgeon's preference and the surgical anatomy of the gastrointestinal system of the patient.

Ondansetron to treat pruritus due to cholestatic jaundice

Intractable itching is a symptom of cholestatic liver disease of various causes that is bothersome and difficult to manage. Although treatment of the primary cause of cholestasis is paramount in resolving the issue, given the debilitating consequences of pruritus, symptomatic treatment is frequently necessary. Although many medications including cholestyramine, rifampin, opioid antagonists (i.e., naloxone, naltrexone), phenobarbital, and antihistamines have been used to treat cholestatic-induced pruritus, none has resulted in uniform success. We report anecdotal success with the use of ondansetron to treat pruritus associated with cholestasis following prolonged intensive care unit course of a 16-year-old. The theories accounting for pruritus with cholestasis are presented, treatment options are reviewed, and the role of ondansetron in the treatment of pruritus is discussed.

Management of cholestatic pruritus in paediatric patients with alagille syndrome: the King's College Hospital experience

OBJECTIVES

The aims of the study were to perform a retrospective observational review of the present management and outcome of cholestatic pruritus in children with Alagille syndrome (AGS) at King's College Hospital and to use results to inform appropriate guidelines.

METHODS

A retrospective review of 62 patients diagnosed as having AGS from January 1995 to November 2010 treated at King's College Hospital was performed. The departmental database of the Paediatric Liver Centre was searched to identify all patients and the clinical records were then analysed.

RESULTS

Fifty-one (82.3%) patients experienced pruritus and 50 (80.6%) received antipruritic medication. Ursodeoxycholic acid was the most prescribed drug (n = 40). Other drugs prescribed were rifampicin (n = 39), cholestyramine (n = 18), naltrexone (n = 14), alimemazine (n = 13), nonsedating antihistamine agents (n = 7), ondansetron (n = 5), and phenobarbitone (n = 1). Albumin dialysis using the molecular adsorbent recirculation system was used in 1 patient. Sixteen patients (25.8%) were listed for liver transplantation, and 11 had undergone transplantation by November 2010. Patient survival was high at 95.2%. Pruritus resolved permanently in 39.2% (n = 20) of patients. Fifty-five percent (n = 11) of such patients had undergone liver transplantation. Pruritus was controlled by medication in 41.2% (n = 21). Itching remained a significant problem, affecting quality of life in 19.6% of patients (n = 10).

CONCLUSIONS

The management of cholestatic pruritus in AGS is difficult and often suboptimal. Pruritus may remain intractable even with combination medical treatment, and at this stage, surgery or liver transplantation is indicated. At our centre, pruritus was successfully treated in 80.4% of patients with medical and surgical management.

Low dose naloxone attenuates the pruritic but not anorectic response to rimonabant in male rats

RATIONALE

Previous research suggests that the acute anorectic effect of cannabinoid CB1 receptor antagonist/inverse agonists may be secondary to response competition from the compulsive scratching and grooming syndrome characteristic of these agents.

OBJECTIVES

As the pruritic effect of rimonabant can be attenuated by the opioid receptor antagonist naloxone, these studies test the prediction that naloxone co-treatment should prevent acute rimonabant anorexia.

METHODS

Two experiments comprehensively profiled the behavioural effects of an anorectic dose of rimonabant (1.5 mg/kg) in the absence or presence of naloxone (experiment 1: 0.01 or 0.1 mg/kg; experiment 2: 0.05 mg/kg).

RESULTS

In both experiments, rimonabant not only significantly suppressed food intake and time spent eating but also induced compulsive scratching and grooming. In experiment 1, although the lower dose of naloxone seemed to weakly attenuate the effects of rimonabant both on ingestive and compulsive behaviours, the higher dose more strongly suppressed the compulsive elements but did not significantly affect the anorectic response. The results of experiment 2 showed that naloxone at a dose which markedly attenuated rimonabant-induced grooming and scratching did not alter the effects of the compound on food intake or time spent feeding. The apparent independence of the ingestive and compulsive effects of rimonabant was confirmed by the observation that despite a 'normalising' effect of naloxone co-treatment on behavioural structure (BSS), the opioid antagonist did not impact the suppressant effect of rimonabant on peak feeding.

CONCLUSION

The acute anorectic response to rimonabant would not appear to be secondary to compulsive scratching and grooming.

The traditional ayurvedic medicine, Eugenia jambolana (Jamun fruit), decreases liver inflammation, injury and fibrosis during cholestasis

BACKGROUND

Cholestasis is a common disease of the liver. Chronic cholestasis eventually leads to hepatic cirrhosis and fibrosis, and rodent chronic cholestasis models are used to study aspects of fibrosis and cirrhosis. Cholestasis-induced liver injury and fibrosis are associated with increased oxidative stress and inflammation. Few pharmacological therapies exist for treatment of cholestasis or cirrhosis, but it is known that humans with better nutritional intake are less likely to develop certain types of cirrhosis. Eugenia jambolana (Jamun) is a tropical berry fruit rich in antioxidant anthocyanin compounds.

AIM

As anthocyanins decrease cellular lipid peroxidation and oxidative stress, it was hypothesized that Jamun fruit extract (JFE) administration could protect against cholestatic liver injury and inflammation in mice.

METHOD

Starting 24 h after sham or bile-duct ligation (BDL) surgery, male C57Bl/6 mice were administered vehicle or JFE (100 mg/kg, po) for 10 days.

RESULTS

Mice that underwent BDL had elevated serum ALT levels, which were reduced to 60% by JFE treatment. Likewise, BDL caused hepatic inflammation, macrophage infiltration, fibrosis and necrosis, all of which were largely improved by JFE. Interestingly, hepatoprotection was observed in JFE-treated BDL mice, despite suppressed transporter expression and increased hepatic bile acid concentrations.

CONCLUSION

Jamun fruit phytochemicals decreased hepatic inflammation and oxidative stress, and protected against hepatocellular injury in mice. Jamun warrants further investigation as a potential antioxidant/anti-inflammatory therapy not only to treat cholestasis but also other liver diseases with an inflammatory component.

Evolving concepts in primary sclerosing cholangitis

Patients suffering from primary sclerosing cholangitis (PSC) show considerable differences regarding clinical manifestations (i.e. large duct versus small-duct PSC, presence or absence of concomitant inflammatory bowel disease), disease progression, risk for malignancy and response to therapy, raising the question whether PSC may represent a mixed bag of diseases of different aetiologies. The growing list of secondary causes and diseases 'mimicking' or even overlapping with PSC (e.g. IgG4-associated sclerosing cholangitis), which frequently causes problems in clear-cut discrimination from classic PSC and the emerging knowledge about potential disease modifier genes (e.g. variants of CFTR, TGR5 and MDR3) support such a conceptual view. In addition, PSC in children differs significantly from PSC in adults in several aspects resulting in distinct therapeutic concepts. From a clinical perspective, appropriate categorization and careful differential diagnosis are essential for the management of concerned patients. Therefore, the aim of the current review is to summarize current and evolving pathophysiological concepts and to provide up-to-date perspectives including future treatment strategies for PSC.

Medical management of chronic liver diseases (CLD) in children (part II): focus on the complications of CLD, and CLD that require special considerations

Treatment of the causes of many chronic liver diseases (CLDs) may not be possible. In this case, complications must be anticipated, prevented or at least controlled by the best available therapeutic modalities. There are three main goals for the management of portal hypertension: (i) prevention of the first episode of variceal bleeding largely by non-selective β-adrenoceptor antagonists, which is not generally recommended in children; (ii) control of bleeding by using a stepwise approach from the least to most invasive strategies; (iii) and prevention of re-bleeding using bypass operations, with particular enthusiasm for the use of meso-Rex bypass in the pediatric population. Hepatic encephalopathy management also consists of three main aspects: (i) ruling out other causes of encephalopathy; (ii) identifying and treating precipitating factors; and (iii) starting empiric treatment with drugs such as lactulose, rifaximin, sodium benzoate, and flumazenil. Treatment of mild ascites and peripheral edema should begin with the restriction of sodium and water, followed by careful diuresis, then large-volume paracentesis associated with colloid volume expansion in severe cases. Empiric broad spectrum antimicrobial therapy should be used for the treatment of spontaneous bacterial peritonitis, bacterial and fungal sepsis, and cholangitis, after taking appropriate cultures, with appropriate changes in therapy after sensitivity testing. Empirical therapies continue to be the standard practice for pruritus; these consist of bile acid binding agents, phenobarbital (phenobarbitone), ursodeoxycholic acid, antihistamines, rifampin (rifampicin), and carbamazepine. Partial external biliary diversion can be used in refractory cases. Once hepatorenal syndrome is suspected, treatment should be initiated early in order to prevent the progression of renal failure; approaches consist of general supportive measures, management of concomitant complications, screening for sepsis, treatment with antibiotics, use of vasopressin analogs (terlipressin), and renal replacement therapy if needed. Hepatopulmonary syndrome and portopulmonary hypertension are best managed by liver transplantation. Provision of an adequate caloric supply, nutrition, and vitamin/mineral supplements for the management of growth failure, required vaccinations, and special care for ensuring psychologic well-being should be ensured. Anticoagulation might be attempted in acute portal vein thrombosis. Some CLDs, such as extrahepatic biliary atresia (EHBA), Crigler-Najjar syndrome, and Indian childhood cirrhosis, require special considerations. For EHBA, Kasai hepatoportoenterostomy is the current standard surgical approach in combination with nutritional therapy and supplemental fat and water soluble vitamins, minerals, and trace elements. In type 1 Crigler-Najjar syndrome, extensive phototherapy is the mainstay of treatment, in association with adjuvant therapy to bind photobilirubin such as calcium phosphate, cholestyramine, or agar, until liver transplantation can be carried out. Treating Indian childhood cirrhosis with penicillamine early in the course of the disease and at doses similar to those used to treat Wilson disease decreases the mortality rate by half. New hopes for the future include extracorporeal liver support devices (the molecular adsorbent recirculating system [MARS®] and Prometheus®), hepatocyte transplantation, liver-directed gene therapy, genetically engineered enzymes, and therapeutic modalities targeting fibrogenesis. Hepapoietin, a naturally occurring cytokine that promotes hepatocyte growth, is under extensive research.

Current management of primary sclerosing cholangitis in pediatric patients

Primary sclerosing cholangitis (PSC) is a chronic cholestatic condition affecting the extrahepatic and intrahepatic biliary tree. The incidence is seemingly increasing in children as a result of increased use of cholangiographic screening techniques in children with inflammatory bowel disease. The clinical presentation of PSC in childhood is variable and frequently without obvious cholestatic features, and cholangiography is essential for the diagnosis of this disorder. Histologic findings may help to exclude autoimmune sclerosing cholangitis. The underlying pathogenesis remains poorly understood and, as a result, therapeutic agents that halt disease progression and improve prognosis are lacking. PSC treatment is mainly supportive and directed at controlling cholestatic symptoms and preventing complications. Ursodeoxycholic acid is helpful in inducing biochemical improvement; long-term pediatric studies to determine a benefit of this agent in young patients are lacking, although results from adult studies have not been promising. Some agents such as antibiotics are under investigation with some promising results. Liver transplantation is required for children who progress to end-stage liver disease. Prospective multicenter trials in children with PSC are needed.

Exploration of Emodin to treat alpha-naphthylisothiocyanate-induced cholestatic hepatitis via anti-inflammatory pathway

Emodin, 1,3,8-trihydroxy-6-methyl-anthraquinone, is an anthraquinone derivative from the roots of Rheum officinale Baill that has been used to treat many diseases in digestive system for thousands of years. This study is to disclose the mechanism of Emodin to treat cholestatic hepatitis via anti-inflammatory pathway. Rats were divided into Emodin, ursodeoxycholic acid, Dexamethasone, model and blank control groups with treatment of respective agent after administration of alpha-naphthylisothiocyanate. At 24 h, 48 h and 72 h time points after administration, liver function, pathological changes of hepatic tissue, tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, myeloperoxidase (MPO), malondialdehyde (MDA), superoxide dismutase (SOD), cytokine-induced neutrophil chemoattractant (CINC)-1, macrophage inflammatory protein (MIP)-2, intercellular adhesion molecule (ICAM)-1, nuclear factor (NF)-kappaB and early growth response (Egr)-1, nitric oxide (NO) and inducible nitric oxide synthase (iNOS) were detected. As a result, compared to the controls, Emodin had a notable effect on rat's living condition, pathological manifestation of hepatic tissue, total bilirubin, direct bilirubin, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) (P<0.05), but had little effect on alkaline phosphatase (ALP), gamma-glutamyltransferase (GGT) and total bile acid. With Emodin intervention, levels of TNF-alpha, IL-6, MPO, MDA, CINC-1, MIP-2, ICAM-1 and translocation of NF-kappaB were remarkably decreased, and levels of NO and iNOS were markedly increased (P<0.05). Emodin had no effect on Egr-1. In conclusion, Emodin has a protective effect on hepatocytes and a restoring activity on cholestatic hepatitis by anti-inflammation. The effects are mainly due to antagonizing pro-inflammatory cytokines and mediators, inhibiting oxidative damage, improving hepatic microcirculation, reducing impairment signals, and controlling neutrophil infiltration.

Endogenous opioids and cannabinoids: system interactions in the regulation of appetite, grooming and scratching

Growing evidence suggests substantial crosstalk between endogenous opioid and cannabinoid systems in the regulation of appetite. Not only is cannabinoid-induced hyperphagia abolished by opioid receptor antagonists (and vice versa), but several laboratories have reported supra-additive anorectic responses following co-administration of opioid and CB1 receptor antagonists. In the present study, videoanalysis has been used to characterise the acute effects of sub-anorectic doses of rimonabant (0.25, 0.75 mg/kg) and naloxone (0.1 mg/kg), alone and in combination, on mash intake, ingestive and non-ingestive behaviour, and post-treatment weight gain in male rats. The results confirmed that, when administered alone, none of these treatments significantly altered mash consumption, various measures of feeding behaviour, or weight gain. Although most non-ingestive behaviours were also unaffected, 0.75 mg/kg rimonabant induced compulsive scratching and grooming. However, when naloxone was given in combination with either dose of rimonabant, both food intake and time spent feeding were significantly decreased while the behavioural satiety sequence (BSS) was accelerated. On further analysis, the co-treatment reductions in food intake and feeding behaviour were found to be of an additive rather than supra-additive nature. Intriguingly, the co-administration of naloxone also virtually abolished the compulsive scratching response to the higher dose of rimonabant. Findings are discussed in relation to current views on the molecular bases of opioid-cannabinoid system interactions and the unexpected 'dual' advantage (reduction in appetite plus attenuation of side-effect) of low-dose combinations of opioid and cannabinoid CB1 receptor antagonists.