Purities in liver diseases
Embed Size (px)
Transcript of Purities in liver diseases
TROPICAL MEDICINE DEPARTEMENTMedical Education Programs
Under the supervision of prof./ Madeha MakhloufProfessor and Chairman of Tropical Medicine Department Program Manager Dr. / Yasser Mahrous Assist. Prof. Of Tropical Medicine Program coordinatorDr. / Hala IbrahemLecturer of Tropical Medicine
Lets Start from the Beginning
Management of purities in liver diseases ByMahmoud Saad Desoky
Lets Start from the Beginning
What is itch ?An unpleasant sensation provoking the desire to scratch
Itch(Latin:pruritus)Itch(Latin:pruritus) is asensationthat causes the desire orreflexto scratch and it is defined as second order nociception because itch has many similarities topain, as both are unpleasantsensoryexperiences, but their behavioral response patterns are different. Pain creates a withdrawal reflex while itch leads to ascratch reflex.Unmyelinatednerve fibersfor itch and pain both originate in theskin; however, information for them is conveyed centrally in two distinct systems that both use the samenervebundle andspinothalamic tract
Itch may dramatically impair the patients quality of life by limiting normal activities, as well as by causing sleep deprivation and even suicidal sensations Indeed, in some patients, pruritus can be so severe that it is an indication for liver transplantation
You know that I would cut offMy hands to help you
But if I did I wouldnt haveAnything to scratch with
And then Id be ofNo use at all.
Don Mc Gonigal, The Itch, 1991
Pruritus can be caused by numerous diseases and hasrecently been classified into six different categories:(1) Dermatological itch, which is associated with primaryskin disorders; (2) Systemic itch, which is caused by systemic diseases, pregnancy, tumors and infectious diseases; (3) Neurological itch, which is induced by anatomical lesions of the peripheral or central nervoussystem;
(4) psychogenic itch, which may occur in differentpsychiatric diseases such as schizophrenia,depression, and tactile hallucinosis; (5) mixed forms of itch in case of coexistence of diseases; and finally(6) other forms of itch the origin of which cannot bedetermined.1 Here, we focus on systemic itch causedby hepatobiliary diseases.
Pruritus is a common symptom of various, mainly cholestatic, hepatobiliary diseases. Both, intra- and extrahepatic cholestasis may cause pruritus Intrahepatic cholestasis may be induced by pure hepatocyte secretory failure as observed in intrahepatic cholestasis of pregnancy (ICP), viral hepatitis, certain forms of drug-induced cholestasis, progressive familial intrahepatic cholestasis (PFIC), and benign recurrent intrahepatic cholestasis (BRIC),.
but also by intrahepatic bile duct damage and secondary hepatocyte secretory failure as observed in primary biliary (PBC), primary sclerosing cholangitis (PSC), and pediatric cholestatic syndromes such as the Alagille syndromeExtrahepatic cholestatic syndromes are less frequently associated with pruritus and are caused by various kinds of extrahepatic biliary obstructions
Patients with cholestatic liver disease frequently reportmost intense itching sensations on the palms and soles, but itch may also be generalized.Pruritus in cholestasis undergoes diurnal variations and is reported by most patients to be most intense in the late evening and early night hours. Specific skin lesions are not observed, but scratching-induced excoriations and prurigo nodularis are common.2 Severity of pruritus can range from mild,in which normal activities of life are limited, moderate in which sleep is disturbed, to severe when normal daily activities become impossibleSigns of chronic liver diseas
Cholestatic liver disease should be considered as a cause of chronic pruritus in any patient who does not show obvious signs of a dermatological disease.
PathogenesisItch perception depends on a complex interplay of receptors, peripheral nerve fibers, intraspinal and cerebral neural pathways, as well as cerebral processing in thalamic nuclei and cortical areasAlthough the pathogenesis of cholestasisrelated pruritus remains poorly understood, peripherally acting pruritogens and altered central neurotransmission have been implicated as causing pruritus in cholestasis
It is well established that itch and pain perception are closely intertwined processes. The previous assumption that itch signals are transmitted via pain-sensitive nerve fibersitch and pain signals are transduced by different subgroups of unmyelinated C-fibers. Thus, itch perception is induced by stimulation of an itch specific subgroup of mechano-insensitive C-nociceptors located in cutis and subcutis
Interestingly, pain (e.g., scratching the skin) represses itch sensation, and antinociception (e.g., intrathecally applied m-opioid receptor agonists or anesthetics) can cause itchItch-specific unmyelinated C-fibres transmit theirsignals from the skin through the dorsal root ganglia toa second neuron in the dorsal horn of the spinal cord,crossing to the contralateral side and projecting via the spinothalamic tract to the ventromedial nucleus of the thalamus. These neurons, which are sensitive to histaminebut insensitive to mechanical stimulation, have been first identified in cats.
The neuroanatomy of pruritus of cutaneous origin
PruritogenFree nerve endings Unmyelinated C nerve fibersDorsal horn of spinal cordContralateral spinothalamic tractPostolateral ventral thalamic nucleusSomatosensory cortex (post central cingulate gyrus)
Direct stimulation of itch-specific C-fibersHistaminePapainKallikreinInterleukin-2 Acethylcholine
Effect via histamine-releaseChymase (triptase) Trypsin (tryptase) Substance P Serotonin Bradykinin
Weak or no pruritogenic effect; potentiates histamineProstaglandins
NeuropeptidesNeurokinin A (NKA), Substance P(SP), Calcitonin gene related peptide (CGRP) Vasoactive intestinal Peptide (VIP)Release from nociceptive C fiberPlays roles in inflammationSP: histamine release from mast cellProteaseMast cell mediators: Tryptase, chymase Have direct pruritic effectsOpioid pruritic effect centrally and peripherally
TreatmentTherapeutic efforts to alleviate pruritus associated with cholestasis should include an adequate therapy of the underlying hepatobiliary disease, which may result in relief of pruritus.In extrahepatic malignant biliary obstruction, stenting, nasobiliary or transcutaneous drainage, or surgical biliodigestive anastomoses are usually effective in eliminating pruritus.21 In intrahepatic cholestasis, a number of therapeutic approaches have been evaluated to alleviate or relieve pruritus
The rationale for medical and interventional therapeutic approaches is:to remove the pruritogens from the enterohepatic cycle by non-absorbable, anion exchange resins such as cholestyramine, colestipol, and colesevelam in mild pruritus or interventions such as nasobiliary and transcutaneous drainage or external biliary diversion in desperate cases
to alter the metabolism of the presumed pruritogens in the liver and/or the gut by biotransformation enzyme inducers such as rifampicin3. to modify central itch and/or pain signalling by influencing the endogenous opioidergic and serotoninergic system via opioid-antagonists and selective serotonin re-uptake inhibitors, respectively;4 . to remove the potential pruritogen(s) from the systemic circulation by invasive methods such as anion absorption,plasmapheresis or extracorporeal albumin dialysis.
Ursodeoxycholic acid (UDCA) exerts beneficial anticholestatic effects and is, therefore, administered to several cholestatic disorders such as primary biliary cirrhosis, primary sclerosing cholangitis, intrahepatic cholestasis of pregnancy, cystic fibrosis-associated liver disease, and paediatric cholestatic syndromes. Although UDCA was reported to effectively diminish itching in some paediatric cholestatic disorders
The anion exchange resins cholestyramine and colestipol have been extensively used to treat cholestatic pruritus and ameliorated pruritus in small trials within 2 weeks. Cholestyramine is recommended as a 4 g dose 1 hour before and after breakfast and may be extended to 44 g/d. Resins should, however, be taken at least 4 hours prior to any other medication as they may interfere with their intestinal absorptionAdverse effects include abdominal discomfort, bloating, diarrhoea, hypertrigliceridemia,and rarely bleeding after long-term use.
The pregnane X receptor (PXR) agonist, rifampicin, is recommended as second line therapy and is thought to exert its antipruritic effect by the induction of phase I, II and III biotransformation enzymes and transporters such as CYP3A4, UGT1A1, SULT2A1 and MRP2 [124,125], thereby enhancing metabolism and/or secretion of potential pruritogens. Additionally, rifampicin may alter intestinal metabolism of potential pruritogens by its antibiotic effect on the intestinal flora.Hepatotoxicity, after treatment for several weeks or months, may be an adverse effect of rifampicin in up to 12% of cholestatic patients
If rifampicin is ineffective, the -opoid antagonist naltrexone should be regarded as third line therapy. Several clinical trials showed a moderate antipruritic effect of naltrexoneat doses of 2550 mg/d [87,88,90,91]. This drug is mostly well-tolerated during long-term treatment. Naltrexone should, however, be started at doses of 12.5 mg/d as severe opiate withdrawal-like reactions may occur in somecholestatic patients during the first days of treatment To prevent a breakthrough ph