Mark G. Swain

Ribavirin as Therapy for Chronic Hepatitis C: A Randomized, Double-Blind, Placebo-Controlled Trial

Hepatitis C virus (HCV) infection is a frequent cause of chronic liver disease, cirrhosis, and hepatocellular carcinoma [1, 2]. Chronic hepatitis C affects an estimated 3 million persons in the United States [3] and ranks second only to alcoholic liver disease as a cause of end-stage liver disease and as a condition necessitating liver transplantation [4]. Currently, the only therapy that has proved to be beneficial in patients with chronic hepatitis C is interferon-. Although effective in eliminating HCV infection in some cases, interferon induces long-term disease remission in only 10% to 25% of patients [5, 6]. Furthermore, interferon- therapy can have intolerable side effects and is expensive. Clearly, other forms of therapy for chronic hepatitis C are needed. Ribavirin is a broad-spectrum, oral, purine nucleoside analog antiviral agent that is similar in structure to guanosine. It is widely used in an aerosol formulation to treat respiratory syncytial virus infections in children [7]. In preliminary trials, an oral preparation of ribavirin was found to improve serum aminotransferase levels in approximately one third of patients with hepatitis C [8-10]. However, a 6-month course of ribavirin therapy was associated with little change in liver histopathology and serum HCV RNA levels. We evaluated the effect of ribavirin administered for a longer period in a randomized, double-blind, placebo-controlled trial. Methods Study Sample Patients enrolled in our trial had compensated chronic hepatitis C and no evidence of other liver disease. Entry criteria included 1) persistent elevations in serum alanine aminotransferase levels that averaged more than twice the upper limit of normal on three measurements made within the previous 6 months; 2) the presence of antibody to HCV [anti-HCV] and HCV RNA in serum; and 3) chronic hepatitis determined by liver biopsy. Exclusion criteria included therapy with other agents, such as interferon, during the previous 6 months; decompensated liver disease; pregnancy or inability to practice birth control; preexisting anemia; serologic evidence of ongoing hepatitis B, hepatitis D, or HIV infection; other significant medical illness; or alcohol abuse (> 60 g/d). Study Design and Treatment After a preliminary period of screening assessments, patients were admitted to the Clinical Center of the National Institutes of Health for medical evaluation and liver biopsy. They were then randomly assigned (using random numbers derived from published tables in blocks of 6, 8, or 10) to receive either ribavirin or placebo. Ribavirin (Virazole, ICN Pharmaceuticals, Costa Mesa, California) was administered as three 200-mg capsules twice daily. Placebo was administered in capsules that were identical in appearance to and given in the same manner as the ribavirin capsules. Therapy was continued for 48 weeks. After starting therapy, patients were evaluated in an outpatient setting once a week for the first month, once every 2 weeks for the second month, then once monthly until 6 months, and bimonthly thereafter. At each visit, patients were interviewed and examined and had blood drawn for routine biochemical and hematologic tests and tests for viral markers. Patients and caregivers were blinded to treatment assignments. The blood test results were also withheld from patients and caregivers but were monitored by an investigator who had no contact with patients during the trial. Compliance was monitored by evaluating the regularity of attendance at clinic visits, by reviewing patient diaries, and by pill count. Maintenance of the blinded nature of the study was assessed by asking patients at the end of the study whether they believed they had received ribavirin or placebo. During the last 2 weeks of treatment, patients again had medical evaluations and liver biopsies, after which the treatment code was broken. Patients who had received placebo were offered treatment with ribavirin in an open trial. Patients who had received ribavirin were followed at 1- to 2-month intervals for at least 6 months. Routine blood tests included complete blood counts and biochemical tests of liver and renal function. Selected serum samples from each patient were tested for anti-HCV (HCV EIA 2.0, Abbott Laboratories, North Chicago, Illinois). They were also tested for HCV RNA by reverse transcription polymerase chain reaction (PCR) using nested primers from the 5 noncoding region of the viral genome [11] and for amount of HCV by the branched DNA (bDNA) signal amplification assay [12] (Quantiplex, Chiron, Emeryville, California). The bDNA assay has a sensitivity of 3.5 105 genome-equivalents per mL, whereas the PCR assay can detect as few as 500 HCV RNA molecules. Genotypes of HCV were determined by reverse hybridization of HCV complementary DNA amplified from serum by reverse transcription PCR [13, 14] (Inno-Lipa, Innogenetics, Brussels, Belgium). Liver biopsy specimens taken before and after therapy were evaluated as a group and read in random order by a single investigator who was blind to the treatment status of each patient. The effect of therapy was assessed by evaluating the degree of necrosis, inflammation, and fibrosis semiquantitatively using the histology activity index [15, 16]. Statistical Analysis Changes in serum aminotransferase levels during therapy were assessed by using repeated-measures analysis of variance. The two treatment groups at entry were compared for similarity using a two-sample Student t-test. In addition, patients were classified as responders, partial responders, or nonresponders on the basis of serum aminotransferase levels during therapy. A complete response was defined as having occurred if the mean of the six bimonthly values for alanine aminotransferase levels fell into the normal range (< 41 U/L [0.69 kat/L]). A partial response was defined as having occurred if the mean of the alanine aminotransferase levels was between 1 and 1.5 times the upper limit of the normal range (41 to 62 U/L [0.69 to 1.04 kat/L]) and was less than 50% of the pretreatment value. All patients who did not have a complete or a partial response were considered nonresponders. These criteria for a definition of response are different from those used in trials of interferon- for chronic hepatitis C [5, 6] but were based on previous experience with ribavirin [8] and were established before the start of the trial. The characteristics before treatment of responders, partial responders, and nonresponders were compared using the Fisher exact test on nominal data or Wilcoxon tests on ordered data. Our trial was approved by the Institutional Review Board of the National Institute of Diabetes and Digestive and Kidney Diseases, and all patients gave written, informed consent. Results Between October 1991 and August 1992, we enrolled 58 patients in the trial (39 men and 19 women, ranging in age from 28 to 66 years [mean age, 44 years]). The known duration of hepatitis ranged from 1 to 26 years (mean duration, 6.3 years). The presumed source of hepatitis was intravenous drug use in 30 patients, blood transfusion in 19 patients, and unknown in 9 patients. Seventeen (29%) patients had previously been treated with interferon-, which had not produced a lasting beneficial effect. Before treatment, HCV RNA was detectable in the serum specimens of all patients by PCR and in the serum specimens of 51 patients (88%) by bDNA assay. The HCV genotype was 1a in 24 patients, 1b in 21 patients, 2a in four patients, 2b in three patients, 3 in four patients, and 4 in one patient. The serum HCV RNA level was not sufficient to allow genotyping in one patient. Twenty-nine patients were randomly assigned to receive ribavirin treatment and 29 were assigned to receive placebo. The initial demographic characteristics and serum biochemical and serologic features of the two groups were similar in all important ways with the exception of the mean hematocrit, which was initially higher in the ribavirin-treated group (Table 1). Table 1. Patient Characteristics by Treatment Group* Therapy was continued for 48 weeks. All patients were followed for the full 48 weeks and all had repeated liver biopsy. Compliance was similar for patients receiving ribavirin and for controls. Thus, of the 13 visits scheduled during therapy for the 58 patients, only 15 (2%) were missed (1.9% for patients receiving ribavirin and 2.1% for controls). Pill counts also suggested excellent compliance, which was similar for patients receiving ribavirin (mean, 96.0%; range, 80.3% to 100%) and for controls (mean, 96.7%; range, 87.4% to 100%). At the time of the liver biopsy that was done at 1 year, patients were asked whether they believed they were receiving ribavirin or placebo. Seven (12%) insisted that they could not tell; among the 51 patients who would guess, 38 (75%) were correct (21 of 26 ribavirin-treated patients [81%] and 17 of 25 controls [68%]). The mean serum alanine aminotransferase levels decreased among the 29 ribavirin-treated patients (P = 0.0001) but not among the 29 controls (Figure 1). The decrease in alanine aminotransferase levels seen with ribavirin therapy occurred predominantly during the first 2 months, and the levels thereafter remained constant at an average of 54% below baseline levels. The mean serum alanine aminotransferase levels (the average of the 6 bimonthly values) during therapy were below baseline levels in all ribavirin-treated patients (ranging from 87% to 9%), with the exception of 1 patient in whom the mean value increased by 49%. Alanine aminotransferase levels reached the normal range and remained within it (complete response) in 6 ribavirin-treated patients (21%) and came to within 1.5 times the upper limit of the normal range (partial response) in another 4 ribavirin-treated patients (14%). No controls had either a complete or a partial response. Thus, defined biochemical responses occurred in 10 of 29 ribavirin-treated patients (35% [95% CI

Effects of naloxone infusions in patients with the pruritus of cholestasis. A double-blind, randomized, controlled trial.

Pruritus is a distressing and frequent complication of cholestasis [1] that is often difficult to manage. It can lead to severe sleep deprivation and may be an indication for liver transplantation. Because the pathogenesis of this form of pruritus is unknown, there is no sound rationale for its management. Thus, it is not surprising that the many medications and procedures that have been used to manage this condition are largely empirically based [2]. It has recently been proposed that a component of the pruritus of cholestasis may be attributable to increased neurotransmission or neuromodulation mediated by the opioid system in the central nervous system [3, 4]. If this hypothesis is correct, not only would the contribution of at least one class of pruritogenic substances (opioids) involved in the pruritus of cholestasis be apparent, but a rationale would be established for using a specific class of drugs, opiate antagonists, in the treatment of the pruritus of cholestasis. Currently, three lines of evidence support the hypothesis that endogenous opioid agonists contribute to the pruritus of cholestasis: 1) the association of increased opioidergic neurotransmission or neuromodulation induced by opiates (such as morphine) with pruritus of central origin that can be reversed by an opiate antagonist (naloxone) [5-9]; 2) clinical and experimental findings suggesting that cholestasis is associated with increased opioidergic tone [10-12]; and 3) preliminary reports of the amelioration of the perception of the pruritus of cholestasis after the administration of opiate antagonists [10, 13, 14]. These observations led to a controlled, single-blinded trial of naloxone infusions for the pruritus of chronic cholestasis [15]. In eight pruritic patients with primary biliary cirrhosis, scratching activity was 29% to 96% (mean, 50%) less during naloxone infusions than during infusions of a placebo solution. This result required confirmation by a double-blind, controlled study. We report the results of a double-blind, placebo-controlled, crossover trial in which 24-hour naloxone infusions and 24-hour placebo infusions were administered consecutively in random order to 29 cholestatic patients with pruritus. Scratching activity was measured continuously throughout the trial by the use of a monitoring system designed for this purpose [16]. Methods The study protocol was approved by the Clinical Research Subpanel of the National Institute of Diabetes and Digestive and Kidney Diseases. All participating patients signed a written informed consent form. Patients Twenty-nine patients with pruritus and cholestasis associated with a cholestatic liver disease or advanced chronic hepatocellular disease were studied. Needle biopsy of the liver or endoscopy and retrograde cholangiography were done when clinically indicated. In each case, causes of pruritus other than cholestasis, (notably, other general medical and psychiatric disorders and pruritic skin diseases) were systematically excluded by taking a comprehensive medical history, doing a full physical examination, and obtaining results of laboratory tests and procedures relevant to each patients medical status. In addition, the results of a careful evaluation by a dermatologist (MLT) had to be negative for a cause of pruritus other than cholestasis. This skin evaluation included examination of the skin under Woods light when appropriate and photography of skin lesions. In addition, post-trial follow-up of the patients studied for 10 to 32 months did not reveal any cause of pruritus other than cholestasis. Exclusion criteria for the trial were the presence of another condition known to be complicated by pruritus (for example, pregnancy, azotemia, thyroid dysfunction, iron deficiency, malignant diseases, and neurologic disorders) and the occurrence of a gastrointestinal hemorrhage, hepatic encephalopathy, or ascites during the previous 6 months. Diagnoses and demographic characteristics of the patients are shown in Table 1. The duration of pruritus was life-long for the patient with the Alagille syndrome, intermittent in the patients with benign recurrent intrahepatic cholestasis although present for at least 1 month before study entry (range, 1 to 12 months), and from 1 to 15 years in the other patients. Among the patients studied, the severity of the pruritus was considered intractable, with severe sleep deprivation, in 6 patients; a major hindrance to regular activities in 20; and tolerable in 3. Serum biochemical profiles on each patient were consistent with cholestasis (median alkaline phosphatase level, 9.67 kat/L [range, 1.3 to 24.4 kat/L; normal, 0.5 to 2.0 kat/L]; median total bilirubin level, 22.3 mmol/L [range, 5.1 to 243 mmol/L; normal, 2.0 to 18 mmol/L]). One patient with chronic hepatitis C had a serum alkaline phosphatase level in the normal range at the time of study. That patient also had a serum bilirubin level of 22.2 mmol/L and fasting and postprandial serum bile acid concentrations that were threefold higher than the upper limit of normal in the absence of features of hepatic decompensation. Table 1. Patient Characteristics In none of the patients was the use of conventional medications for the pruritus of cholestasis associated with clinically acceptable relief from pruritus. Seventeen of the patients had been treated with cholestyramine, antihistamines, or phenobarbital in various combinations. Another patient, who could not tolerate cholestyramine, received antihistamines. One patient with primary biliary cirrhosis had been receiving ursodeoxycholic acid for treatment of cholestasis for 2 years with no apparent effect on pruritus. Therapy with ursodeoxycholic acid, which was not classified as an antipruritic medication, was not discontinued. The patient with the Alagille syndrome had been given rifampicin for pruritus. Therapy with this drug had been discontinued several months before her participation in the trial when the patient developed neuropathy. Study Design Therapy with all antipruritic medications was discontinued 5 days before the study began. During the trial, each patient received four consecutive 24-hour intravenous infusions in an arm vein, with no intervals between infusions. The nursing staff provided conventional maintenance of the intravenous cannula. Two of the infusions consisted of 5% dextrose/0.45% NaCl (placebo), and two contained naloxone (Narcan; DuPont, Manati, Puerto Rico) (0.2 g/kg body weight per minute) in 5% dextrose/0.45% NaCl. The total volume infused during 24 hours was 0.5 L. Each naloxone infusion was preceded by an intravenous bolus injection of 0.4 mg of naloxone in 1 mL of normal saline, and each placebo infusion was preceded by an intravenous bolus injection of 1 mL of normal saline. The order of naloxone and placebo infusions was assigned by balanced randomization. The patients, nursing staff, and clinicians were blinded to the content of the infusions and the bolus injections. Only the statistician (DWA) and the designated pharmacy staff knew of the randomization code. Vital signs were continuously recorded every hour throughout the study by an automated blood pressure monitor (Critikon Corp., Tampa, Florida). Any symptoms or abnormal signs occurring during the infusions, including those compatible with a reaction similar to an opiate withdrawal syndrome, were carefully assessed. Assessment of Pruritus Perception and Scratching Activity Patients were asked to record the severity of their pruritus by making a mark with pen or pencil on a visual analog scale every 4 hours while awake. The scale consisted of a 10-cm horizontal line; 0 cm (the beginning of the scale on the left side) represented no itching and 10 cm (the end of the scale on the right side), the worst itching ever. A visual analog score was the number of centimeters (to the nearest millimeter) between 0 cm and the point on the scale at which the patient made a mark [15, 17]. Scratching activity, independent of limb movements, was continuously recorded during the infusions. The monitoring system used consists of a vibration (scratch) transducer (Piezo Film Division, Altochem Corp., Philadelphia, Pennsylvania), an FM transmitter and receiver (Radio Shack [32-1221]), a custom-made signal processor, and a personal computer. The vibration transducer was taped to the middle fingernail of the dominant hand, and the fingernail was not cut during the study. The transducer consists of a rectangular piece of piezoelectric film, 1 cm2 in area, 28mthick and metallized on both sides with silver ink. It is connected by a thin cable to the transmitter box (2 7 6 cm), which is attached to the same arm by a Velcro cuff. The transducer converts the strain produced by vibrations of the fingernail as it traverses the skin in the act of scratching to an electrical voltage. The electrical signal is transmitted across the room, where it is received, processed, and logged by the personal computer as a scratching activity index in units of counts per unit time (30 seconds). Only signals above a preset threshold and within the frequency band shown by Fourier analysis to be associated with vibrations of the scratching fingernail (50 to 1000 Hz) were recorded [15, 16]. The validity of this index as an accurate quantitative measurement of scratching activity has been confirmed by independent observations and examination of videotapes [16]. Statistical Analysis In this four-period crossover trial [18], each patient was assigned to receive, without interruption, four 24-hour infusions (two of naloxone and two of placebo), the order of which was chosen by balanced randomization from the six possible arrangements. All of the infusion bags and their contents were identical in appearance. Twenty-three patients received all four infusions, four received three, and two received one naloxone infusion and one placebo infusion. The balance achieved in the infusion assignment was as follows: Infus

Endogenous opioids accumulate in plasma in a rat model of acute cholestasis

To obtain data on the degree to which the opioid system is changed in cholestasis, endogenous opioid activity in plasma of rats with acute cholestasis was determined 5 days after bile duct resection. Total plasma opioid activity was determined using a radioreceptor technique that measured the displacement of the opiate receptor ligand [3H]-DAMGO from lysed synaptosomal fractions of normal rat brain. Plasma total opioid activity was threefold greater in bile duct-resected rats than in sham-operated and unoperated controls (P less than or equal to 0.05). Plasma levels of the individual endogenous opioid, methionine-enkephalin, were determined using a sensitive radioimmunoassay, and the specificity of the assay was confirmed using high-performance liquid chromatography. In cholestatic rats, plasma methionine-enkephalin levels were more than six-fold greater than in sham-operated controls (P less than or equal to 0.001) and more than 17-fold greater than in unoperated controls (P less than or equal to 0.001). However, plasma methionine-enkephalin levels accounted for less than 5% of total plasma opioid activity after bile duct resection. Plasma methionine-enkephalin levels in both cholestatic plasma and plasma from sham-operated animals were stable when incubated in vitro despite the presence of undiminished activity of the major enkephalin-degrading enzymes. Thus, protection of methionine-enkephalin from degradation may be a factor contributing to the elevated plasma levels of methionine-enkephalin found in cholestasis. The magnitude of the increase in plasma endogenous opioid activity in bile duct-resected rats provides support for the hypothesis that endogenous opioids contribute to the pathophysiology of cholestasis.

Central mu-opioid receptors are down-regulated in a rat model of cholestasis

Ameliorations of the pruritus of cholestasis by opioid antagonists are consistent with this form of pruritus being centrally mediated by the opioid system. To determine whether the central opioid system is altered in cholestasis, the specific binding of a selective mu-opioid receptor ligand, 3H-DAMGO, to mu-opioid receptors was studied in rats with acute cholestasis due to bile duct resection. Using whole brain membranes and subcellular mitochondrial-synaptosomal fractions the density of mu-receptor sites was 30% (p less than 0.01) and 22% (p = 0.03) less in bile-duct-resected rats than in sham-resected rats. Using membranes from individual brain regions specific binding of 3H-DAMGO was reduced by 43-53% in the cerebral cortex, hippocampus and caudate nucleus of bile-duct-resected rats. Thus mu-opioid receptors in the brain are down-regulated in a classical model of cholestasis. This alteration of the central opioid system could be a consequence of increased exposure of opioid receptors to endogenous opioids in cholestasis and may reflect an important mechanism in the pathogenesis of the pruritus of cholestasis.

Therapy of chronic hepatitis B with a 6-month course of ribavirin

Ribavirin is a nucleoside analogue with broad spectrum antiviral activity that has been shown to inhibit viral replication in the woodchuck model of hepatitis B virus infection. We studied the effect of ribavirin on viral replication in 18 patients with chronic hepatitis B who were positive for hepatitis B e antigen. Patients were randomized to receive a 24-week course of oral ribavirin at a dose of either 800, 1000, or 1200 mg/kg per day. All patients completed 24 weeks of treatment and an additional 24 weeks of follow up without significant side effects except for mild, reversible hemolytic anemia. Response to ribavirin was similar among all three dosage groups (p > 0.5); hence the data were pooled and analyzed together. Mean hepatitis B virus DNA levels decreased from 162.7 (95% confidence interval, 106 to 219) pg/ml before treatment to its lowest level of 114.3 (95% confidence interval, 53 to 175) pg/ml at week 20 (p < 0.05). Two patients became negative for HBV DNA and lost hepatitis B e antigen. Mean serum alanine aminotransferase activity decreased markedly from 131.1 (95% confidence interval, 84 to 178) U/l before treatment to 62.4 (95% confidence interval, 48 to 77) U/l at the end of 24 weeks of ribavirin (p < 0.05) and became normal in four patients (22%). Aminotransferase levels returned to baseline within 4 weeks once ribavirin was discontinued, while HBV DNA concentrations remained below baseline even at the end of 24 weeks of follow up.(ABSTRACT TRUNCATED AT 250 WORDS)

Sympathetic nerves, but not the adrenal gland, contribute to elevated plasma levels of met-enkephalin in rats with acute cholestatic hepatitis

Met-enkephalin is known to circulate in human and animal plasma in low levels. However, the source(s) of plasma met-enkephalin have not been completely elucidated. It has been proposed that the adrenal gland, sympathetic nerves, pancreas and the gut might be implicated. Recently, markedly elevated levels of met-enkephalin have been documented in the presence of liver disease. To investigate potential sources of met-enkephalin in liver disease, rats with acute cholestatic hepatitis 24 h after gavage with alpha naphthylisothiocyanate (ANIT) 100 mg/kg were studied. Plasma met-enkephalin levels were determined by radioimmunoassay in plasma samples from normal, adrenalectomized, or chemically sympathectomized animals. In control rats, ANIT treatment resulted in a striking 8.7-fold increase in systemic venous met-enkephalin levels (inferior vena cava) (P < or = 0.0005) and a significant increase in peptidase-derived met-enkephalin levels (determined after trypsin/carboxypeptidase B digestion of plasma samples) (P < or = 0.05). ANIT-treatment also resulted in a 5.6-fold increase in portal vein met-enkephalin levels (P < or = 0.005). Portal vein met-enkephalin levels were only 1.2-fold higher than IVC levels in ANIT-treated rats (P < or = 0.05). Plasma activities of the two main enkephalin degrading enzymes, aminopeptidase and enkephalinase, were similar in control and ANIT-treated rats. Chemical sympathectomy, prior to ANIT treatment, decreased the elevation in inferior vena caval met-enkephalin levels by 35% (P < or = 0.005). Adrenalectomy did not alter ANIT-induced increases in circulating met-enkephalin levels (pNS).(ABSTRACT TRUNCATED AT 250 WORDS)

Methionine enkephalin accumulates in plasma but not in brain or cerebrospinal fluid of rats with acute toxic hepatitis

In order to determine whether acute toxic hepatitis in the rat is associated with an accumulation of methionine enkephalin in plasma and increased blood-to-brain transfer of methionine enkephalin, immunoreactive methionine enkephalin levels were determined by radioimmunoassay in plasma, cerebrospinal fluid and whole brain samples from rats with thioacetamide induced acute toxic hepatitis. Thioacetamide treatment was associated with an 8.7-fold increase in plasma immunoreactive methionine enkephalin levels (P less than or equal to 0.005) 24 h after treatment. However, this marked elevation in plasma immunoreactive methionine enkephalin levels was not associated with an increase in whole brain or cerebrospinal fluid immunoreactive methionine enkephalin levels. These data suggest that increased plasma-to-brain transfer of methionine enkephalin does not occur in this model of acute toxic hepatitis.

Open-label trial of oral nalmefene therapy for the pruritus of Cholestasis

The aims of this study were to determine whether long-term oral administration of the opiate antagonist nalmefene is associated with any beneficial effects in patients with pruritus secondary to cholestatic liver disease and to assess the safety of long-term administration of this drug to these patients. Fourteen patients with unrelieved chronic pruritus of cholestasis were studied. Scratching activity, independent of limb movements, was recorded continuously for 24-hour periods before and during treatment with an initial ameliorating dose of nalmefene. Simultaneously, during these periods, visual analogue scores (VASs) of pruritus were recorded every 4 hours while patients were awake. The dose of nalmefene, which initially was 2 mg orally twice daily, was increased during the study, usually until a satisfactory clinical response was achieved. Five patients experienced a transient opioid withdrawal-like reaction that did not preclude continuing with nalmefene therapy. Serum biochemical indices of cholestasis did not change appreciably during treatment. Thirteen patients reported amelioration of the perception of pruritus on nalmefene. In 5 patients, exacerbations of pruritus occurred approximately 4 weeks after an initial ameliorating dose had been reached; these exacerbations were managed by increasing the dose. Baseline mean values for VAS and scratching activity were higher than corresponding means during nalmefene therapy in 13 (P = .002) and 12 (P = .013) patients, respectively. Possible tolerance to nalmefene occurred in 3 patients. Three patients experienced marked exacerbation of pruritus after nalmefene therapy was suddenly discontinued. Blood levels of nalmefene were consistent with normal pharmacokinetics of the drug. These results suggest that nalmefene may have a favorable risk-to-benefit ratio when it is administered orally long-term to patients with the pruritus of cholestasis.

Effect of inhibition of ornithine decarboxylase activity in a model of acute hepatocellular necrosis.

Objective The effect of blockade of the enzyme ornithine decarboxylase by difluoromethylornithine (DFMO) on hepatocellular necrosis and survival in rats treated with thioacetamide (TAA) was investigated. Design In one experiment, the effect of DFMO on survival of rats with TAA-induced acute hepatocellular necrosis was determined. In another experiment, blood and liver specimens were obtained from DFMO or saline-treated rats 24 h after the administration of TAA for determinations of serum alanine aminotransferase (ALT) and liver content of polyamines and microsomal cytochrome P-450 and for assessment of hepatic histology. Methods Liver polyamines were determined by reversed-phase HPLC and microsomal cytochrome P-450 content by dithionite-difference spectroscopy of CO-treated homogenates. The severity of hepatocellular necrosis was scored blindly. Results TAA-treated rats that received DFMO survived longer than saline-treated controls (P<0.01). Serum ALT and liver putrescine concentrations were lower and the histological severity of acute hepatocellular necrosis was less in DFMO-treated rats with TAA-induced hepatocellular necrosis than in saline-treated controls (P<0.05, P < 0.01 and P < 0.05, respectively). Total cytochrome P-450 levels were similar in DFMO and saline-treated rats with TAA-induced hepatocellular necrosis. Conclusions DFMO increases survival in TAA-induced fulminant hepatic failure by decreasing the severity of acute hepatocellular necrosis. The beneficial effects of DFMO do not appear to be mediated by its effects on polyamine metabolism, but may be attributable to an effect of DFMO on thioacetamide metabolism or on an alternative pathway of ornithine metabolism.