Fulminant hepatitis with severe lactate acidosis in HIV-infected patients on didanosine therapy

Acute liver failure associated with antiretroviral treatment for HIV: a report of six cases

BACKGROUND/AIMS

Severe hepatotoxicity is a rare but potentially fatal side effect of all antiretrovirals. We report a series of six human immunodeficiency virus (HIV)-infected patients admitted with acute liver failure (ALF) over a 25-month period, of whom five died. All had been treated with a range of antiretroviral therapy and only two had had acquired immune deficiency syndrome (AIDS) defining illnesses.

RESULTS

Median duration of antiretroviral therapy was 12.5 months (range 1-23). Median time from the introduction of new antiretroviral therapy to the onset of ALF was 8 weeks (range 2-12). The development of ALF was unrelated to duration of HIV treatment or type of antiretroviral therapy, and was not predicted by close out-patient supervision and monitoring of liver function. Biochemical investigations were variable but revealed a predominantly hepatocellular pattern. Liver biopsy revealed typical features of mitochondrial toxicity in only one case, with confluent hepatocellular necrosis, inflammation and cholestasis seen in the others.

CONCLUSIONS

There is a need to increase awareness of the potential hepatotoxicity of antiretroviral therapy and to develop means of predicting its development. With increasing usage of antiretroviral therapy, severe hepatotoxicity and ALF may arise more frequently, and the outcome is poor despite intensive supportive therapy.

Symptomatic elevations of lactic acid and their response to treatment manipulation in human immunodeficiency virus-infected persons: a case series

Symptomatic lactic acidemia was seen in 5 human immunodeficiency virus-positive patients receiving combination therapy that included stavudine and > or =1 other nucleoside. Peak venous lactic acid levels of 3.1-7.4 mmol/L (normal range, 0.5-2.1 mmol/L) were associated with fatigue and rapid weight loss, whereas withdrawal of antiretrovirals led to normalization of venous lactic acid levels, symptomatic improvement, and weight gain. Resumption of an altered therapeutic regimen, which did not include stavudine but did include other nucleosides in 4 of 5 cases, did not result in recurrence of the syndrome after up to 126 days.

Hyperlactatemia and antiretroviral therapy: the Swiss HIV Cohort Study

The prevalence, clinical presentation, and risk factors for hyperlactatemia among patients receiving antiretroviral therapy was determined during a 1-month period for patients in the Swiss HIV Cohort Study. Overall, 73 (8.3%) of 880 patients presented an increase in serum lactate of >1.1 times the upper normal limit (UNL). For 9 patients (1%), lactate elevation was moderate or severe (>2.2 times the UNL). Patients who presented with hyperlactatemia were more likely to be receiving stavudine with or without didanosine (odds ratio, 2.7; 95% confidence interval, 1.5-4.8), as compared with patients who received zidovudine-based regimens. The risk increased with increasing time receiving stavudine with or without didanosine. The association between hyperlactatemia and stavudine with or without didanosine was not biased by these medications being more recently available and, therefore, being given preferentially to patients who had prolonged use of nucleoside analog reverse-transcriptase inhibitors. Hyperlactatemia was associated with lipoatrophy, hyperlipidemia, and hyperglycemia. Age, sex, or stage of infection with human immunodeficiency virus were not predictive of hyperlactatemia. Determination of lactate levels may prove useful in the screening for mitochondrial toxicity.

Symptomatic lactic acidosis in hospitalized antiretroviral-treated patients with human immunodeficiency virus infection: a report of 12 cases

We retrospectively investigated the clinical and histopathologic features of hospitalized patients infected with human immunodeficiency virus who had symptomatic lactic acidosis syndrome at a university teaching hospital during 1995-2000. Twelve patients were identified, 11 during 1998-2000; of these, 5 died with rapid progression to otherwise unexplained multiple-organ failure. All had extensive prior exposure to nucleoside analog reverse-transcriptase inhibitors (NRTIs). At presentation, the most commonly identified NRTI component of antiretroviral regimens was stavudine plus didanosine. Eleven patients presented with abdominal pain, nausea, and/or emesis. Eight patients had prior acute weight loss (mean [+/-SD], 12+/-5.3 kg). Median venous plasma lactate levels were > or =2-fold greater than the upper limit of normal (2.1 mmol/L). Serum transaminase levels were near normal limits at presentation. Histopathologic studies confirmed hepatic macrovesicular and microvesicular steatosis in 6 patients. Concurrent chemical pancreatitis was identified in 6 patients. The increasing number of cases identified during the study period suggests that physicians better recognize symptomatic lactic acidosis and/or that cumulative NRTI exposure may increase the risk for this syndrome.

Antiretroviral hepatotoxicity in human immunodeficiency virus-infected patients

BACKGROUND

Drug hepatotoxicity is a potentially serious adverse reaction of antiretroviral therapy in human immunodeficiency virus-infected patients. The impact of this problem in the routine treatment of patients with human immunodeficiency virus infection is poorly defined.

OBJECTIVES

Our aim was to determine what clinical features are associated with hepatotoxicity in human immunodeficiency virus-infected patients receiving antiretroviral therapy.

METHODS

Consecutive patients in a primary care-based human immunodeficiency virus clinic were evaluated for hepatotoxicity. Clinic records were used to obtain patient characteristics, as well as independent variables including CD4+ count, coexisting hepatitis C and current alcohol use.

RESULTS

Sixty-five patients taking antiretroviral therapy were evaluated. Twenty-four were identified to have antiretroviral hepatotoxicity. An age over 40 years (P=0.019), an absolute CD4+ count of less than 310 cells/mL (P=0.002) and coexisting hepatitis C infection (P=0.035) were significantly associated with hepatotoxicity. Patients older than 40 years had a sevenfold increased risk (risk ratio, 6.9; 95% confidence interval, 1.7-27.3) and those with an absolute CD4+ count of less than 310 cells/mL had a tenfold increased risk (risk ratio, 10.2; 95% confidence interval, 2.5-41.9) for antiretroviral hepatotoxicity, in comparison with those who were younger or who had a greater absolute CD4+ count. Of the eight patients documented to have coexisting hepatitis C infection, six (75%) were in the antiretroviral hepatotoxicity group.

CONCLUSIONS

An age older than 40 years and an absolute CD4+ count of less than 310 cells/mL were significantly associated with antiretroviral-induced hepatotoxicity. The majority of our patients with chronic hepatitis C had hepatotoxicity from antiretroviral therapy.

Direct analysis of mitochondrial toxicity of antiretroviral drugs

OBJECTIVES

Mitochondrial toxicity is a serious side-effect of antiretroviral drugs, especially nucleoside reverse transcriptase inhibitors (NRTI). An in vitro assay to predict mitochondrial toxicity of in-use and developmental NRTI would be invaluable. To test the ability of a cytofluorimetric technique to predict the mitochondrial-dependent pancreatic and hepatic toxicity we used didanosine (ddI) alone or in combination with hydroxyurea (HU).

METHODS

The technique is based on the ability of the lipophilic cation JC-1 to enter selectively into mitochondria and change its colour as the membrane potential changes due to toxicity. Mitochondrial toxicity by HU and ddI was evaluated in pancreatic and hepatic human cell lines. The results were expressed as mitochondrial toxicity index (MTI), ranging from 0 to 100: the negative control was 0, and 100 indicating maximal toxicity.

RESULTS

Dose-dependent pancreatic toxicity of ddI was evident after 14 days of culture (MTI 34 +/- 4 at 100 microM, 10 +/- 4 at 10 microM, 2 +/- 3 at 1 microM ddI). HU alone was not toxic (MTI 7 +/- 10 at 100 microM, 2 +/- 2 at 50 microM and 2 +/- 4 at 10 microM HU); however, HU increased the toxicity of high, but not low, concentrations of ddI. For example, the MTI of 10 microM ddI plus 50 microM HU was 54 +/- 9. Negligible mitochondrial toxicity was observed in the hepatic cell line exposed to ddI alone or in combination with HU.

CONCLUSIONS

This in vitro assay might have in vivo relevance. First, ddI-related pancreatitis is dose dependent, and is reported more frequently than hepatic failure, consistent with our in vitro results. Second, patients who developed pancreatitis during randomized, controlled trials were treated with HU in combination with 400 mg ddI once daily (high peak concentration of ddI in the blood). In contrast, no pancreatitis was observed when HU was combined with 200 mg ddI twice daily (low peak concentration of ddI). These in vivo results are consistent with our in vitro observation that HU increases pancreatic cell toxicity in the presence of high concentrations of ddI. The in vitro assay described here might be used to predict the mitochondrial toxicity of other NRTI, alone or in combination.

Antiretroviral-Induced Hepatic Steatosis and Lactic Acidosis: Case Report and Review of the Literature

As the prevalence of human immunodeficiency virus (HIV) infection continues to rise the clinician is encountered with a diagnostic challenge. Nonsurgical diseases such as acute colitis or enteritis can appear similar to such true surgical emergencies as abscess, perforation, or mesenteric ischemia. We report a case of fulminant hepatic failure associated with didanosine and masquerading as a surgical abdomen and compare the clinical, biologic, histologic, and ultra-structural findings with reports described previously. This entity should be kept in mind when evaluating the acute abdomen in the HIV-positive patient.

Drug-induced liver disease

This year's review is divided into several sections: the first describes drug withdrawals and new general reviews of drug-induced liver disease (DILD), including a review of a classification of drug injury. We review agents newly described as causing DILD, and new reports of DILD from established agents appearing in the year 2000. New aspects regarding the treatment of acetaminophen toxicity are included, and in the final section we deal with prevention of DILD as well as issues surrounding the use of potentially hepatotoxic medications in patients with underlying chronic disease.

Hyperlactataemia in HIV-Infected Patients: The Role of NRTI-Treatment

Background

Long-term treatment with nucleoside reverse transcriptase inhibitors (NRTIs) can induce mitochondrial dysfunction, most severely represented by lactic acidosis. Diagnostic tests for mitochondrial dysfunction are lacking, although persistently elevated serum lactate might be a surrogate marker.

Objectives

To determine the occurrence of hyperlactataemia in HIV-infected patients on NRTI-treatment and to evaluate the possible risk factors.

Methods

Cross-sectional analysis of lactic-acid levels in asymptomatic HIV-infected patients. Hyperlactactaemia was considered mild if between 2.0–5 mmol/l, serious if >5 mmol/l and lactic acidosis was defined as lactic acid levels >5 mmol/l with bicarbonate <20 mmol/l. Possible risk factors, such as current and preceding NRTI-treatment as well as treatment with non-nucleoside reverse transcriptase inhibitors or protease inhibitors and concurrent liver disease, were analysed.

Results

Two hundred and twenty three asymptomatic HIV-infected patients were studied, including 174 patients (78%) on NRTI treatment, 12 patients (5%) treated without NRTIs and 37 patients (17%) not treated. Mild hyperlactataemia was found in 42 patients (19%), from whom 38/42 (90%) were NRTI-treated and the remaining patients (4/42, 10%) received no treatment (χ2, P<0.05). The significant risk factors for hyperlactataemia in the univariate analysis were NRTI-treatment as a group ( P=0.03) and elevated ALT ( P=0.008). In multivariate analysis NRTI use ( P=0.05) and ALT level ( P=0.03) remained a significant determinant of hyperlactataemia. Among the different individual NRTIs, a stavudine-containing ( P=0.004) and a zalcitabine-containing ( P=0.07) regimen were most notably associated with the development of hyperlactataemia, whereas for the combinations of NRTIs, such association was only found for stavudine/lamivudine ( P=0.05).

Conclusions

A correlation between hyperlactataemia and NRTI treatment was found, but the value of routine lactate measurement for individual treatment monitoring remains uncertain.

Osteopenia in HIV-infected men: association with asymptomatic lactic acidemia and lower weight pre-antiretroviral therapy

BACKGROUND

Osteopenia has been associated with antiretroviral therapy, particularly with protease inhibitors. Osteopenia in HIV-uninfected men is associated with mitochondrial defects.

METHODS

Bone density was assessed by dual-energy X-ray absorptiometry (DEXA) in 221 HIV-infected men (mean age 43 years) recruited to a lipodystrophy prevalence survey. Additional parameters assessed were demographics, exercise, smoking, type(s) and duration of all antiretroviral therapy, lipodystrophy (overall and by region), CD4 counts, HIV RNA, fasting metabolic parameters (lipid, glycaemic, lactate, liver enzymes, testosterone) and regional body fat and lean mass (DEXA and L4 abdominal computed tomographic scan).

RESULTS

Thirty-two patients were drug-naive; 42 were receiving nucleoside analogue reverse transcriptase inhibitors (NRTI) and 147 were receiving these plus protease inhibitors. Osteoporosis (t-score < -2.5 SD below normal) was found in seven (3%) and osteopenia (t-score -1.0 to -2.5 SD) in 44 (22%). No patient had had a fracture since being infected with HIV. The only factors independently associated on logistic regression with osteopenia or osteoporosis were higher lactate levels, even if asymptomatic [odds ratio (OR) 2.39 per 1 mmol/l increase; 95% confidence interval (CI) 1.39-4.11; P = 0.002), and lower weight prior to commencing antiretroviral therapy (OR 1.06 per 1 kg decrease; 95% CI 1.02-1.11; P = 0.006). There was no independent association with any other parameter, including type or duration of antiretroviral therapy and lipodystrophy at any site. Lower total bone mineral density was associated with lower weight prior to commencing antiretroviral therapy whereas lower spinal bone mineral density was associated mostly with higher lactate.

CONCLUSION

Osteopenia in HIV-infected men is common, asymptomatic and is associated with asymptomatic NRTI-related lactic acidemia and lower weight pre-antiretroviral therapy.

Elevated lactate levels in hospitalized persons with HIV infection

Lactic acidosis has been described in persons with HIV infection particularly in association with the use of nucleoside reverse transcriptase inhibitors (NRTIs). Little is known about the epidemiology of this problem. We reviewed the records of all HIV-infected adults with elevated lactate levels admitted to Barnes-Jewish hospital from 1996 to 1998. There were 37 patients identified with elevated lactate levels. The annual rate of elevated lactate levels was 22.6, 33.9, and 30.8 per 1,000 admissions in 1996, 1997, and 1998, respectively. The median age of the patients was 40.4 years; median CD4(+) count was 148 cells/mm(3); and the median HIV-1 RNA level was 4,401 copies/ml. The median lactate level was 4.5 mmol/liter (range, 2.2-19 mmol/liter). Twenty-nine patients (78%) had elevated lactate levels at admission. Elevated lactate levels were associated with sepsis (48.7%), pancreatitis (13.5%), liver failure (8.1%), multiorgan failure (8.1%), and other conditions. Five patients had lactic acidosis associated with the use of antiretroviral medications; one patient with unexplained lactic acidosis and four patients with pancreatitis. The mortality rate was 45.9% (17/37). Higher lactate levels were associated with increased mortality. In conclusion, elevated lactate levels were uncommon but not rare in hospitalized patients with HIV infection. Sepsis was the most commonly associated condition and antiretroviral medications were the second most frequently associated factor. There was no significant increase in the annual rate of lactic acidosis during this 3-year period.

The management of the clinical complications of antiretroviral therapy

In clinical practice, combination antiretroviral therapy is frequently complicated by adverse reactions and drug-related toxicities. The incidence, presentation, differential diagnosis, and management of the most frequent and severe of these complications are discussed. The recently described spectrum of metabolic complications, including hyperlipidemia, fat redistribution, and lactic acidosis, are covered in detail. The management of nephrotoxicity, pancreatitis, bone marrow suppression, peripheral neuropathy, and hypersensitivity reactions related to antiretroviral therapy is also discussed.

Significant Toxicities Associated with Antiretroviral Therapy

Use of at least three potent antiretroviral agents has become the standard of care in the management of HIV infection. The potential toxicities associated with highly active antiretroviral therapy (HAART) however, may limit a patient’s ability to adhere to and tolerate these agents. Although a comprehensive discussion of all toxicities associated with HAART is beyond the scope of this article, selected short-term and long-term significant toxicities will be reviewed. Short-term toxicities that will be discussed include abacavir-induced hypersensitivity reactions, efavirenz-associated central nervous system side effects and rash associated with the non-nucleoside reverse transcriptase inhibitors (NNRTIs) and the protease inhibitor (PI) amprenavir. Several long-term toxicities associated with the nucleoside reverse transcriptase inhibitors (NRTIs) are hypothesized to be due to mitochondrial toxicity. These toxicities include myositis and lactic acidosis with hepatic steatosis, pancreatitis and peripheral neuropathy. Some experts also hypothesize that mitochondrial toxicity is responsible for the lipodystrophy syndrome, which includes hyperglycemia, abnormal fat redistribution and dyslipidemia. Finally, indinavir-associated nephrolithiasis, which may present with either short term or long term use will be discussed. This article will provide the practicing pharmacist with a review of these significant toxicities, the implicated agents, incidence, usual clinical presentation, and recommendations for management.

Hyperlactatemia and hepatic abnormalities in 10 human immunodeficiency virus-infected patients receiving nucleoside analogue combination regimens

During a 6-and-a-half month period, we identified 10 human immunodeficiency virus (HIV)-infected men who were receiving antiretroviral regimens, including nucleoside analogues, and who developed unexplained reproducible hyperlactatemia in association with either abdominal symptoms or an unaccounted-for elevated alanine aminotransferase level, or both. After careful consideration of the possible etiologies, antiretrovirals were discontinued; lactate levels normalized in all patients. The estimated incidence of this phenomenon in our clinic was 20.9 cases per 1000 person-years of nucleoside analogue treatment. These observations extend the spectrum of the nucleoside analogue-induced lactic acidosis/hepatic steatosis syndrome by the identification of a subtle and perhaps earlier form, which has characteristic symptoms and laboratory abnormalities, and a favorable prognosis on discontinuation of antiretroviral therapy.

Lactic acidosis associated with nucleoside analog therapy in an HIV-positive patient

A 44-year-old African-American female, HIV positive treated with highly active antiretroviral therapy (HAART), consisting of two nucleoside analogues and one nonnucleoside reverse transcriptase inhibitor, who was initially admitted with severe lactic acidosis. Liver biopsy was performed on the ninth hospital day, which revealed moderate microvesicular and macrovesicular fatty changes. The possible mechanism of lactic acidosis in patients on nucleoside analogues is discussed. The question as to how to monitor for this syndrome, as usual tests are neither sensitive nor specific, still remains important.

An Introduction to Nucleoside and Nucleotide Analogues

The introduction of newer and more potent agents has diverted attention away from the importance of nucleoside analogue reverse transcriptase inhibitors (NRTIs) in modern antiretroviral drug regimens. As a class, these proviral chain terminators lack the virological potency of either non-nucleoside reverse transcriptase inhibitor (NNRTI) or protease inhibitor (PI) drugs, due largely to their competitive mode of inhibition and requirement for metabolic activation. However, neither NNRTIs nor PIs alone can maintain the complete suppression of HIV replication required for extended therapy, and both suffer from serious class cross-resistance on therapeutic failure. Thus, the NRTIs will remain essential components of highly active antiretroviral therapy (HAART) for the foreseeable future, both for their contribution to a regimen's virological potency and the subsequent preservation of the more potent drug classes used with them. However, it has become apparent in recent years that the current NRTIs exhibit duration-dependent adverse events as a class, which may limit the length of time for which they can be safely used. An independent contribution to peripheral fat wasting in lipodystrophy syndrome has been established for the use of NRTI drugs. Of greater clinical concern is their established association with potentially fatal lactic acidaemia and hepatic steatosis. Both these class events, as well as several individual drug events, such as peripheral neuropathy, can be linked to progressive mitochondrial destruction with a greater or lesser degree of confidence. Mitochondrial toxicity, due in large part to the high affinity of several NRTI agents for uptake by mitochondrial DNA polymerase γ, has been demonstrated both in vitro and in vivo. New chain-terminating agents are urgently needed that address issues of improved virological potency, greater efficacy in NRTI-experienced individuals, and greater long-term safety. The nucleotide class of reverse transcriptase inhibitor (NtRTI), currently under clinical development, addresses improved potency by abbreviating the intracellular activation pathway to allow a more rapid and complete conversion to the active agent. These nucleoside monophosphate analogues are taken as masked prodrugs bearing labile lipophilic groups to facilitate penetration of target cell membranes. Subsequent unmasking by endogenous chemolytic enzymes releases a partially activated nucleoside analogue metabolite. The NtRTI furthest along the developmental process is tenofovir disoproxil fumarate (TDF), an orally available acyclic adenine phosphonate analogue, currently in Phase III clinical trials. This agent has shown high potency and an unusually durable response in trials of single-agent therapy intensification in highly treatment-experienced individuals, and its active metabolite, tenofovir diphosphate, exhibits a long intracellular half-life in both resting and activated peripheral blood mononuclear cells that permits once daily dosing. Tenofovir diphosphate also exhibits a very low affinity for DNA polymerase γ in vitro, suggesting a low degree of in vivo mitochondrial toxicity may be observed on long-term follow-up, although clinical data to support this inference are not yet available. The introduction of TDF and other NtRTIs as ‘second-generation’ nucleoside analogues carefully evaluated for potential long-term toxicity, can be expected to significantly improve the therapeutic options for both those currently on HAART and those yet to begin.

Severe lactic acidosis induced by nucleoside analogues in an HIV-infected man

Nucleoside analogues can induce myopathy or hepatitis by means of mitochondrial dysfunction. We report the case of a 31-year-old man infected with HIV who had a severe lactic acidosis without muscle or liver symptoms. He improved after hemodialysis and withdrawal of antiviral drugs. Muscle and liver evaluation allowed us to ascribe lactic acidosis to a mitochondriopathy induced by zidovudine and didanosine.

Zidovudine-induced mitochondrial disorder with massive liver steatosis, myopathy, lactic acidosis, and mitochondrial DNA depletion

Zidovudine is known to be responsible for a mitochondrial myopathy with ragged-red fibres and mitochondrial DNA depletion in muscle. Lactic acidosis alone or associated with hepatic abnormalities has also been reported. A single report mentioned the concomitant occurrence of muscular and hepatic disturbances and lactic acidosis in a patient receiving zidovudine, but muscle and liver tissues were not studied. A 57-year-old man with AIDS, who had been treated with zidovudine for 3 years, developed fatigue and weight loss. Serum creatine kinase and hepatic enzyme levels were high. Lactic acidosis was present. Liver biopsy showed diffuse macrovacuolar and microvacuolar steatosis. After withdrawal of zidovudine, creatine kinase, aspartate aminotransferase, and alanine aminotransferase levels normalised within 5 days, and lactacidaemia decreased. Acidosis persisted. The patient became confused and febrile and died 8 days after detection of high blood lactic acid. A muscle sample obtained at autopsy showed mitochondrial abnormalities with ragged-red fibres and lipid droplet accumulation. Southern blot analysis showed depletion of mitochondrial DNA, affecting skeletal muscle and liver tissue. No depletion was found in myocardium and kidney. This case emphasises that zidovudine treatment can induce mitochondrial multisystem disease, as revealed in our case by myopathy, liver steatosis and lactic acidosis.

Antiviral activity and toxicity of fialuridine in the woodchuck model of hepatitis B virus infection

Woodchucks were used to study the antiviral activity and toxicity of fialuridine (FIAU; 1,-2'deoxy-2'fluoro-1-beta-D-arabinofuranosyl-5-iodo-uracil). In an initial experiment, groups of six chronic woodchuck hepatitis virus (WHV) carrier woodchucks received daily doses of FIAU by intraperitoneal injection for 4 weeks. At 0.3 mg/kg/d, the antiviral effect was equivocal, but at 1.5 mg/kg/d, FIAU had significant antiviral activity. No evidence of drug toxicity was observed during the 4-week period of treatment or during posttreatment follow-up. In a second experiment, groups of nine WHV carriers or uninfected woodchucks were given 1.5 mg/kg/d of FIAU orally for 12 weeks, and the results compared with placebo-treated controls. After 4 weeks, the serum WHV-DNA concentration in the FIAU-treated carrier group was two to three logs lower than that in the placebo-treated group. After 12 weeks of FIAU treatment, serum WHV DNA was not detectable by conventional dot-blot analysis, hepatic WHV-DNA replicative intermediates (RI) had decreased 100-fold, and hepatic expression of WHV core antigen was remarkably decreased. No evidence of toxicity was observed after 4 weeks, but, after 6 to 7 weeks, food intake decreased and, after 8 weeks, the mean body weights of woodchucks treated with FIAU were significantly lower than controls. Anorexia, weight loss, muscle wasting, and lethargy became progressively severe, and all FIAU-treated woodchucks died or were euthanized 78 to 111 days after treatment began. Hepatic insufficiency (hyperbilirubinemia, decreased serum fibrinogen, elevated prothrombin time), lactic acidosis, and hepatic steatosis were characteristic findings in the final stages of FIAU toxicity in woodchucks. The syndrome of delayed toxicity in woodchucks was similar to that observed previously in humans treated with FIAU, suggesting that the woodchuck should be valuable in future investigations of the molecular mechanisms of FIAU toxicity in vivo and for preclinical toxicological evaluation of other nucleoside analogs before use in patients.

Principles of clinical pharmacology in postexposure prophylaxis

Deciding on postexposure prophylaxis for any infection requires that the patient and healthcare provider understand the magnitude of infection risk and the adverse consequences of therapeutic intervention or nonintervention. Principles of epidemiology and microbiology allow us to estimate the risk of infection. Principles of clinical pharmacology allow us to estimate the risk and benefit of therapy. The dose-response-time relationships for antiviral activity and toxicity of a drug can be used to develop regimens that maximize benefit and minimize risk. Other important pharmacologic considerations include the role of active and toxic drug metabolites, combination chemotherapy, drug interactions, and medication compliance.

Dideoxyinosine-induced pancreatitis in human immunodeficiency virus-infected children

Dideoxyinosine (ddI) is a widely used antiretroviral agent in treatment of HIV infection. Pancreatitis is a serious side effect. Two cases are reported, one with rapid development of a pseudocyst.

Hepatic failure and lactic acidosis due to fialuridine (FIAU), an investigational nucleoside analogue for chronic hepatitis B

BACKGROUND

We describe severe and unexpected multisystem toxicity that occurred during a study of the antiviral nucleoside analogue fialuridine (1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)-5-iodouracil, or FIAU) as therapy for chronic hepatitis B virus infection.

METHODS

Fifteen patients with chronic hepatitis B were randomly assigned to receive fialuridine at a dose of either 0.10 or 0.25 mg per kilogram of body weight per day for 24 weeks and were monitored every 1 to 2 weeks by means of a physical examination, blood tests, and testing for hepatitis B virus markers.

RESULTS

During the 13th week lactic acidosis and liver failure suddenly developed in one patient. The study was terminated on an emergency basis, and all treatment with fialuridine was discontinued. Seven patients were found to have severe hepatotoxicity, with progressive lactic acidosis, worsening jaundice, and deteriorating hepatic synthetic function despite the discontinuation of fialuridine. Three other patients had mild hepatotoxicity. Several patients also had pancreatitis, neuropathy, or myopathy. Of the seven patients with severe hepatotoxicity, five died and two survived after liver transplantation. Histologic analysis of liver tissue revealed marked accumulation of microvesicular and macrovesicular fat, with minimal necrosis of hepatocytes or architectural changes. Electron microscopy showed abnormal mitochondria and the accumulation of fat in hepatocytes.

CONCLUSIONS

In patients with chronic hepatitis B, treatment with fialuridine induced a severe toxic reaction characterized by hepatic failure, lactic acidosis, pancreatitis, neuropathy, and myopathy. This toxic reaction was probably caused by widespread mitochondrial damage and may occur infrequently with other nucleoside analogues.