Serious Adverse Cutaneous and Hepatic Toxicities Associated With Nevirapine Use by Non???HIV-Infected Individuals

Pharmacogenetic Considerations in the Management of HIV Infection

Potent combination antiretroviral drug therapy has now been available to HIV-infected patients for more than a decade, resulting in a significant decline in disease-related morbidity and mortality. Nonetheless, a number of HIV-infected individuals fail to experience the full benefit of their antiretroviral medications; some lack a robust virologic response, while others experience treatment-limiting toxicities. A number of factors may contribute to variable drug response in patients with HIV infection. Virologic, immunologic, pharmacologic, and pharmacokinetic differences between HIV-infected patients have all been noted to contribute to interpatient variability in drug response. Recent data suggest that pharmacogenetic differences among HIV-infected individuals may also be an important variable that contributes to antiretroviral drug response. Pharmacogenetic studies of antiretroviral drug therapy have explored the influence of single nucleotide polymorphisms in genes responsible for key proteins involved in antiretroviral drug metabolism (cytochrome P50 enzymes) and drug transport (P-glycoprotein). In addition, the human leukocyte antigen genotype (HLA-B*57) has been found to predict abacavir-associated hypersensitivity reactions. Antiretroviral pharmacogenetics offers the possibility of optimizing virologic response and minimizing drug toxicity by individualizing anti-HIV pharmacotherapy. The authors review those genetic polymorphisms that have been shown, or are strongly suspected, to influence antiretroviral drug metabolism, transport, and toxicity.

Postexposure prophylaxis after sexual exposure to HIV

Increasing numbers of international, national and state/provincial health organizations in the developed and developing world recommend postexposure prophylaxis (PEP) following potential sexual exposure to HIV. The evidence for these policies is extrapolated from occupational healthcare worker, perinatal prophylaxis and animal studies. There is no direct evidence of PEP efficacy after sexual exposures. Studies addressing potential increases in risk behavior, toxicities and cost–effectiveness are encouraging. Considerations for offering PEP include the timing and characteristics of the exposure and the HIV status of the source and exposed individuals. PEP includes 28 days of a combination antiretroviral drug regimen containing two or more drugs and associated laboratory testing, counseling and referrals. PEP service delivery challenges include ensuring adequate access to services, optimizing PEP adherence and facilitating follow-up HIV testing and counseling. Men who have sex with men, sexual assault survivors, children and adolescents, and individuals in resource-limited settings present unique needs and challenges.

Postexposure prophylaxis after sexual exposure to HIV

PURPOSE OF REVIEW

HIV postexposure prophylaxis is often recommended following potential sexual exposure to HIV. Recent data address the effectiveness of postexposure prophylaxis and prevention counseling, cost-effectiveness, antiretroviral options, challenges with nonoccupational postexposure prophylaxis among adolescents and children and following sexual assault in high HIV prevalence areas, and a successful program in Amsterdam.

RECENT FINDINGS

Postexposure prophylaxis is not completely protective. Seroconversion may result from antiretroviral failure or from ongoing exposures. Postexposure prophylaxis associated risk reduction counseling results in reductions in subsequent risk behavior. Programs that target outreach and limit prescriptions to those with exposure sources who are at risk of being HIV infected are cost-effective. Less restrictive guidelines result in more prescriptions for low-risk exposures; this practice is not cost-effective. The ideal antiretrovirals for postexposure prophylaxis use have not been established. Tenofovir has several attractive properties. Developing systems to support the effective delivery of postexposure prophylaxis among children and adolescents and following sexual assault in high HIV prevalence, resource limited settings is challenging.

SUMMARY

Numerous national and international guidelines recommend postexposure prophylaxis following potential sexual exposure to HIV. Maximizing adherence and minimizing subsequent HIV exposures will be critical to enhancing the effectiveness of this HIV prevention intervention.

Reacciones de hipersensibilidad a antirretrovirales en pacientes con infección por el virus de la inmunodeficiencia humana

Drug hypersensitivity reactions in the HIV-positive patient are a major problem in management of these patients and, nowadays the antiretroviral agents are the main cause of those reactions, exceeding cotrimoxazole. The present review focuses on immunologic reactions that have been reported associated with antiretroviral agents. We have reviewed case reports on Medline(R) to September 2005. Evidence that these reactions are immune mediated is largely based on the typical symptomatology and few studies have been done to determine the pathogenesis mechanisms. The clinical management of this type of reactions is complex because of differential diagnosis and of potential severity. It is essential that research is now carried out into the pathogenic mechanisms and so, we shall be able to offer an efficacious protocol to manage these situations.

Adverse cutaneous drug eruptions and HIV: a clinician's global perspective

Adverse drug reactions (ADRs) are common and mostly avoidable. Some ADRs cannot as yet be predicted, but at-risk populations/patients and high-risk drugs are identifiable. HIV-infected patients are at risk of developing cutaneous ADRs, especially Stevens-Johnson syndrome, toxic epidermal necrolysis, and drug hypersensitivity syndrome. Multiple factors of causation variably present in patients with HIV infection best explain the pathogenesis of these cutaneous ADRs. When no effective alternate therapy is available, drug rechallenge in HIV-infected patients can be attempted with little morbidity or mortality if done according to rationalized protocols.

Liver transplantation for fulminant hepatitis related to nevirapine therapy

Drug-induced hepatotoxicity is an important cause of hepatocellular injury. Non-nucleoside retroviral transcriptase inhibitors are known to cause hepatotoxicity. We describe a detailed case of fulminant hepatitis induced by nevirapine (Viramune) and treated by liver transplantation.

Interaction between fosamprenavir, with and without ritonavir, and nevirapine in human immunodeficiency virus-infected subjects

Fosamprenavir (FPV) with and without ritonavir (RTV) was added to the antiretroviral regimens of human immunodeficiency virus-infected subjects receiving nevirapine (NVP) to evaluate this drug interaction. Significant reductions in plasma amprenavir exposure (25 to 35%) were observed following coadministration of 1,400 mg of FPV twice a day (BID) and 200 mg of NVP BID. A regimen of 700 mg of FPV BID plus 100 mg of RTV BID may be coadministered with NVP without dose adjustment.

Maternal hepatotoxicity with nevirapine as part of combination antiretroviral therapy in pregnancy

OBJECTIVES

To describe the maternal tolerability of nevirapine as part of combination antiretroviral therapy in pregnancy at three HIV centres in Dublin, Ireland and to determine risk factors for development of significant hepatotoxicity.

METHODS

A retrospective study was carried out of all women prescribed nevirapine as part of combination antiretroviral therapy in pregnancy at three HIV centres in Dublin, Ireland (October 2000 to February 2003). Toxicities experienced were graded according to the Division of AIDS toxicity guidelines for adults. Statistical analysis was performed to determine whether there were differences between those that did and those that did not experience significant hepatotoxicity.

RESULTS

A total of 123 women initiated nevirapine as part of combination antiretroviral therapy in the study period. Eight women developed significant hepatotoxicity, including two women who died from fulminant hepatitis. Women who experienced more severe hepatotoxicity had higher pretreatment CD4 counts (P=0.01).

CONCLUSIONS

In this cohort, women who experienced more severe hepatotoxicity had higher pretreatment CD4 counts, lending additional weight to the need for caution in using nevirapine as part of combination antiretroviral therapy in women not requiring antiretroviral therapy for their own health.

Increased adverse drug reactions to antimicrobials and anticonvulsants in patients with HIV infection

OBJECTIVE

To review the incidence, signs, symptoms, and mechanisms of adverse drug reactions (ADRs) to sulfonamides, anticonvulsants, and antimycobacterial medications among people with HIV.

DATA SOURCES

Searches of MEDLINE/PubMed (1980-November 2005) and National Library of Medicine Meeting Abstracts (1989-November 2005), as well as hand searches of journals and abstracts, were conducted to identify primary literature. Reference lists were reviewed to identify additional relevant reports.

STUDY SELECTION AND DATA EXTRACTION

Relevant articles and abstracts, particularly of in vitro experiments and clinical studies, were compiled and reviewed.

DATA SYNTHESIS

ADRs, especially in HIV-infected patients, are a cause for concern. Sulfonamides, anticonvulsants, and antimycobacterial drugs are commonly used to prevent and treat complications of HIV, including seizures and opportunistic infections. Patients with HIV have a much greater rate of ADRs to these drug classes, including severe and life-threatening hypersensitivity reactions. Several mechanisms of these ADRs have been postulated. Sulfamethoxazole and anticonvulsant hypersensitivity may involve the increased formation and decreased detoxification of reactive metabolites. The mechanisms for the marked increase in hypersensitivity ADRs to antimycobacterial drugs may be related to an altered immune profile in patients infected with both tuberculosis and HIV.

CONCLUSIONS

ADRs to antimicrobial and anticonvulsant therapy cause markedly increased morbidity and mortality in HIV-positive patients. Further research involving the interaction between HIV and the increased ADRs to these drugs is required.

HLA-dependent hypersensitivity to nevirapine in Sardinian HIV patients

BACKGROUND

Hypersensitivity reaction to nevirapine, which in some cases can be fatal, shows a higher prevalence in Sardinia in comparison with other Italian regions.

OBJECTIVE

This study demonstrates that hypersensitive reaction to nevirapine in Sardinian HIV-infected patients is associated with the HLA Cw8-B14 haplotype. These two HLA class I antigens are in strong linkage disequilibrium in the Sardinian population.

METHODS

Forty-nine Sardinian HIV-positive patients treated with nevirapine were studied. Thirteen (26%), developed a hypersensitive reaction thus requiring the drug to be discontinued. HLA class I and II molecular typing was performed in both nevirapine-hypersensitive and nevirapine-tolerant patients. To avoid biased representation of the allele frequencies in the two groups of treated patients, molecular typing was also performed in 82 HIV-positive patients who had not been treated with nevirapine.

RESULTS

Considerable overlap was observed for the clinical, immunological and demographic characteristics of the 13 hypersensitive patients and 36 tolerant patients. Clinical parameters included viral load, status of HIV infection, CD4 and CD8 cell counts, hepatitis C virus/hepatitis B virus co-infections. Forty-six percent (6/13) of the nevirapine-hypersensitive subjects had the HLA-Cw8 and HLA-B14(65) antigens compared with 5% (2/36) of the nevirapine-tolerant group (P = 0.004; Pc = 0.05).

CONCLUSION

In agreement with other recent reports, the utility of HLA typing in HIV patients to identify genetic factors that may confer susceptibility to drug-induced hypersensitive reaction was confirmed. A careful choice of antiretroviral therapy in susceptible individuals should significantly reduce the risk of severe hypersensitive reaction.

Ritonavir, Saquinavir, and Efavirenz, but Not Nevirapine, Inhibit Bile Acid Transport in Human and Rat Hepatocytes

Human immunodeficiency virus-infected patients on antiretroviral drug therapy frequently experience hepatotoxicity, the underlying mechanism of which is poorly understood. Hepatotoxicity from other compounds such as bosentan and troglitazone has been attributed, in part, to inhibition of hepatocyte bile acid excretion. This work tested the hypothesis that antiretroviral drugs modulate hepatic bile acid transport. Ritonavir (28 microM), saquinavir (15 microM), and efavirenz (32 microM) inhibited [(3)H]taurocholate transport in bile salt export pump expressing Sf9-derived membrane vesicles by 90, 71, and 33%, respectively. In sandwich-cultured human hepatocytes, the biliary excretion index (BEI) of [(3)H]taurocholate was maximally decreased 59% by ritonavir, 39% by saquinavir, and 20% by efavirenz. Likewise, in sandwich-cultured rat hepatocytes, the BEI of [(3)H]taurocholate was decreased 100% by ritonavir and 94% by saquinavir. Sodium-dependent and -independent initial uptake rates of [(3)H]taurocholate in suspended rat hepatocytes were significantly decreased by ritonavir, saquinavir, and efavirenz. [(3)H]Taurocholate transport by recombinant NTCP and Ntcp was inhibited by ritonavir (IC(50) = 2.1 and 6.4 microM in human and rat, respectively), saquinavir (IC(50) = 6.7 and 20 microM, respectively), and efavirenz (IC(50) = 43 and 97 microM, respectively). Nevirapine (75 microM) had no effect on bile acid transport in any model system. In conclusion, ritonavir, saquinavir, and efavirenz, but not nevirapine, inhibited both the hepatic uptake and biliary excretion of taurocholate.

Antiretroviral therapy: an update for the non-AIDS specialist

PURPOSE OF REVIEW

The treatment of HIV infection has been transformed by the introduction of highly active antiretroviral therapy. For patients who respond and can tolerate lifelong therapy, HIV infection may become a chronic disease requiring long-term ambulatory care follow-up. The current management of antiretrovirals is increasingly complex because of the large number of agents, wide spectrum of toxicities, adherence issues, and drug interactions. This review summarizes the currently available agents, recommended and alternative combinations, commonly encountered adverse events, and viral resistance issues.

RECENT FINDINGS

Twenty antiretroviral medications are commercially available in the United States. Six new agents have been introduced since 2000, including one drug in a novel class of HIV fusion inhibitors. The adverse effects of antiretrovirals are well characterized and include lactic acidosis related to nucleoside reverse transcription inhibitors; metabolic and body habitus changes, primarily attributed to protease inhibitors; and concern about the long-term vascular consequences of elevated lipids and insulin resistance associated with treatment. The recommended antiretroviral therapy by an expert panel as of October 2004 is summarized.

SUMMARY

The benefits of antiretroviral therapy are clear: reduced morbidity and mortality related to advanced HIV infection. Managing antiretroviral therapy, along with their adverse effects and drug interactions, is complex. Modern treatment mandates a thorough understanding of the agents. Consultation with an HIV-experienced clinician should be considered in most circumstances.

Genetic analysis of simian immunodeficiency virus expressed in milk and selectively transmitted through breastfeeding

To develop effective intervention strategies that prevent breast milk transmission of human immunodeficiency virus (HIV), we must understand the specific viral properties and mechanisms responsible for infant infection. We have used lactating rhesus macaques infected with a pathogenic simian immunodeficiency virus (SIV) stock to analyze the viral genotypes expressed in plasma and milk throughout the disease course and to identify those variants ultimately transmitted to infants through breastfeeding. In these studies we observed mother-to-infant transmission of SIV/Delta(B670) by eight females during the chronic phase of disease, and we analyzed by heteroduplex tracking assays and sequence analysis the distribution and fluctuations in viral genotypes expressed. Each female expressed multiple V1 envelope genotypes in milk near the time of transmission, while a single genotype was found in each of the infants. Variants transmitted to infants were not expressed throughout the maternal disease course but were only detected near the time of transmission. The emergence of the transmitted genotype in the dam typically occurred in plasma before milk and was coincident with increased milk viral loads. Transmitted genotypes tended to be longer and more glycosylated and had a less negative charge over the V1 region compared to viral genotypes expressed in milk but not transmitted. These observations demonstrate that specific viral genotypes are selectively transmitted to infants through breastfeeding and support the hypothesis that transmission occurs as genotypes adapt for efficient expression in milk.

Evidence of an immune-mediated mechanism for an idiosyncratic nevirapine-induced reaction in the female Brown Norway rat

Previously, we reported a new animal model of an idiosyncratic drug reaction in which nevirapine causes a skin rash in some rats that has characteristics similar to the reaction that occurs in humans. Strong evidence that the reaction is immune-mediated was found; specifically, low-dose pretreatment induced tolerance, while with rechallenge, the time to onset decreased and the severity increased. Furthermore, splenocytes from rechallenged rats transferred rash susceptibility to naïve recipients. We now report the results of studies to explore the immune aspects of this reaction. T cells were found to play an important role, as demonstrated by their ability to adoptively transfer susceptibility to the skin reaction. Of these T cells, CD4+ cells are the likely effectors because they were capable of transferring susceptibility and the reaction was delayed in rats partially depleted of CD4+ T cells. In contrast, it appears that CD8+ T cells are not essential, as CD8+ T cells were unable to transfer sensitivity to a naïve animal and rats depleted of CD8+ T cells still developed skin rash. Unlike the penicillamine model, where we have demonstrated that the tolerance induced by low-dose treatment is immune-mediated, tolerance induced by low-dose nevirapine appears to be largely due to induction of metabolism as it can be overcome by inhibition of cytochrome P450. Pretreatment with the immunosuppressants, cyclosporine and tacrolimus, prevented the rash and even led to resolution of the rash during nevirapine treatment. These studies reinforce the hypothesis that the reaction in this model is similar to that which occurs in humans. In particular, the finding that CD4+ T cells may play a central role in this model fits with the observation that the incidence of idiosyncratic reactions to nevirapine in humans appears to be lower in patients with low CD4+ counts.

Predicting and diagnosing abacavir and nevirapine drug hypersensitivity: from bedside to bench and back again

There is a growing discussion surrounding the issue of personalized approaches to drug prescription based on an individual's genetic makeup. This field of investigation has focused primarily on identifying genetic factors that influence drug metabolism and cellular disposition, thereby contributing to dose-dependent toxicities and/or variable drug efficacy. However, pharmacogenetic approaches have also proved valuable in predicting drug hypersensitivity reactions in selected patient populations, including HIV-infected patients receiving long-term antiretroviral therapy. In this instance, susceptibility has been strongly linked to genetic loci involved in antigen recognition and presentation to the immune system--most notably within the major histocompatibility complex (MHC) region--consistent with the notion that hypersensitivity reactions represent drug-specific immune responses that are largely dose independent. Here the authors describe their experiences with the development of pharmacogenetic approaches to hypersensitivity reactions associated with abacavir and nevirapine, two commonly prescribed antiretroviral drugs. It is demonstrated that prospective screening tests to identify and exclude individuals with a certain genetic makeup may be largely successful in decreasing or eliminating incidence of these adverse drug reactions in certain populations. This review also explores the broader implications of these findings.

Growing importance of liver disease in HIV-infected persons

Liver disease is a growing problem in HIV-infected persons. In those who are able to take antiretroviral therapy, the forms of liver disease have changed and their relative importance has increased. This review focuses on liver disease in HIV-infected persons, caused by hepatitis C virus, hepatitis B virus, or treatment of HIV infection.

Tolerance of a short course of nevirapine, associated with 2 nucleoside analogues, in postexposure prophylaxis of HIV

A combination of 2 nucleoside analogues and 1 protease inhibitor is usually recommended in postexposure prophylaxis. Because of the complex treatment schedule and frequent adverse effects, however, this regimen is often not completed. Therefore, since January 2000, we have used nevirapine (NVP), 200 mg/d, for only 4 days in combination with 2 nucleoside analogues for 1 month to improve adherence and completion rates. We present a 2-year retrospective analysis on 120 individuals who received this prophylaxis. Only 2 subjects stopped NVP because of a clinical event, whereas 10 interrupted the nucleoside analogues. We observed 3 (2.8%) of 104 slight alanine aminotransferase (ALT) increases in the first 2 weeks of treatment (grade 1). Three additional (month 1 or 3) ALT augmentations also occurred (also grade 1). No HIV or hepatitis C virus seroconversion occurred during follow-up. Twenty-nine (38.2%) of 76 individuals and 21 (47.7%) of 44 individuals were seen 3 months after nonoccupational and occupational exposure, respectively. We believe that such a short course (4 days) of 200-mg NVP treatment once a day in combination with 2 nucleoside analogues for 1 month is clinically and biologically safe.

Once-Daily Regimen of Saquinavir, Ritonavir, Didanosine, and Lamivudine in HIV-Infected Patients With Standard Tuberculosis Therapy (TBQD Study)

OBJECTIVES

To assess the efficacy and safety of a once-daily regimen with didanosine, lamivudine, saquinavir, and low-dose ritonavir in antiretroviral (ARV)-naive patients with tuberculosis treated with rifampin and the influence of rifampin on plasma trough concentration (Ctrough) of saquinavir.

METHODS

Single-arm, prospective, multicenter, open-label pilot study, including 32 adult ARV-naive subjects with HIV infection and tuberculosis under standard treatment that included rifampin (600 mg q.d.) and isoniazid (300 mg q.d.). After 2 months of tuberculosis treatment, patients were started on once-daily ARV therapy, consisting of didanosine, lamivudine, ritonavir (200 mg), and saquinavir soft gel capsules (1600 mg). HIV RNA level, CD4 cell count, clinical and laboratory toxicity, and saquinavir Ctrough during and after antituberculosis therapy were analyzed.

RESULTS

After 48 weeks of follow-up, 20 of 32 patients (62.5%; 95% CI: 45.8% to 79.2%) in the intent-to-treat population and 20 of 28 (71.4%; 95% CI: 54.4% to 88.4%) in the on-treatment population had an HIV RNA level <50 copies/mL. Treatment tolerance was acceptable in all patients except for 2 with biologic hepatic toxicity leading to discontinuation. Seven patients had virologic failure. In 10 patients (36%), saquinavir Ctrough was <0.05 microg/mL during tuberculosis therapy and 5 of them had virologic failure. The median saquinavir Ctrough was 44% lower (interquartile range: 19% to 71%) with coadministration of rifampin than without.

CONCLUSION

The combination of didanosine, lamivudine, saquinavir, and ritonavir may be a useful treatment regimen for patients with tuberculosis in whom a once-daily protease inhibitor-containing regimen is considered indicated. Nevertheless, on the basis of pharmacokinetic profile the dose of 1600/200 mg of saquinavir/ritonavir cannot be recommended. Further studies with higher doses of saquinavir (2000 mg) boosted with ritonavir are warranted.

The use of a triple nucleoside-nucleotide regimen for nonoccupational HIV post-exposure prophylaxis

OBJECTIVES

Nonoccupational post-exposure prophylaxis (NPEP) for HIV is recommended after high-risk sexual exposure. Because of the high incidence of intolerable side effects observed with protease inhibitor- and zidovudine-based NPEP regimens, our unit changed standard NPEP treatment to 28 days of tenofovir-lamivudine-stavudine (TDF-3TC-d4T). The aim of this study was to compare side effects and numbers of individuals completing NPEP before and after this change.

METHODS

Parameters were compared amongst individuals commencing the following NPEP regimens: zidovudine-lamivudine (ZDV-3TC), zidovudine-lamivudine-nelfinavir (ZDV-3TC-NFV) and TDF-3TC-d4T.

RESULTS

A total of 385 individuals received ZDV-3TC (n = 36), ZDV-3TC-NFV (n = 225) or TDF-3TC-d4T (n = 137) as NPEP for the first time between June 1999 and November 2003. Noncompletion rates were 25%, 32% and 15%, respectively (P = 0.001), with odds ratios for noncompletion being 2.0 [95% confidence interval (CI) 0.8-4.8] and 2.7 (95% CI 1.6-4.8) in the first two groups compared with the TDF-3TC-d4T group (P = 0.008). Adverse events were less common in the TDF-3TC-d4T group, with significantly lower rates of nausea and headache, but significantly higher rates of peripheral neuropathy and asymptomatic raised transaminases. There was no HIV seroconversion in any group.

CONCLUSIONS

TDF-3TC-d4T is significantly better tolerated than ZDV-3TC or ZDV-3TC-NFV as NPEP and results in greater numbers of individuals completing 28 days of treatment.

Toxicité mitochondriale hépatique associée au traitement par les antirétroviraux

Highly active antiretroviral therapy (HAART) has become the gold standard treatment of HIV/AIDS infection. NRTI-related mitochondrial toxicity has been recognized as a serious adverse effect of HAART. The mechanisms underlying NRTI-induced mitochondriopathy involve the inhibition of the human DNA polymerase gamma mtDNA mutations and oxidative stress. The clinical spectrum of NRTI-related toxicity ranges from a subclinical disease e.g. mild hepatic abnormalities, to a rare life-threatening condition with lactic acidosis and hepatic insufficiency. In the latter, liver histology shows massive steatosis. Ultrastructural assessment of mitochondrial abnormalities may be of help to address the NRTI toxicity in poorly symptomatic patients. Efforts have been recently made to assess the clinical relevance of non-invasive tests including the evaluation of mtDNA or mitochondrial functions in peripheral blood mononuclear cells for the diagnosis of NRTI-associated toxicity.

Arzneimittelexantheme bei Therapie der HIV-Infektion mit Efavirenz und Nevirapin

Efavirenz and nevirapine are frequently used drugs in antiretroviral therapy. Rashes are common side effects of these drugs. In this study, we examined the characteristics of efavirenz- and nevirapine-associated rashes. This prospective nonrandomized multicenter study included 662 HIV-infected patients (efavirenz: 325, nevirapine: 337) to determine incidence, duration, cross-reactivity, and outcome upon reexposure. Of the treated patients, 4.5% (n=30) developed rashes (nevirapine: 2.4% and efavirenz: 6.4%). In four patients treatment was not interrupted. Three patients were re-exposed to the initial drug without any side effects. Therapy with nevirapine or efavirenz does not have to be interrupted if rashes exhibit no blistering, mucosal manifestations, or systemic signs.

Protection of healthcare workers from bloodborne pathogens

PURPOSE OF REVIEW

For decades, healthcare workers have been known to be at risk from acquiring a variety of bloodborne pathogen infections as a result of occupational exposure. Primary prevention of exposures, as recommended by universal precautions guidelines, remains the cornerstone of protecting healthcare workers. Nonetheless, a substantial number of parenteral exposures continue to occur. Updated developments are summarized here, and recommendations for the protection of healthcare workers from bloodborne pathogens are provided.

RECENT FINDINGS

The predominant evidence suggests that total percutaneous injuries have decreased over the last decade. Thoughtful adherence to universal precautions remains the primary means of preventing occupational exposures and thus of reducing occupational risk of infection with bloodborne pathogens. A number of studies have provided additional evidence for the efficacy of safety devices in reducing specific subsets of injuries when combined with education and administrative interventions. Barriers to and positive predictors of universal precautions compliance have been identified. Postexposure prophylaxis remains the second line of defense; several authorities have now recommended three antiretroviral agents in this setting.

SUMMARY

In summary, almost two decades of experience with universal/standard precautions has resulted in a decrease in parenteral injuries, but much work remains to be done. Vaccines, effective infection control procedures, safer procedures, and safer devices will all be necessary, along with a better understanding of factors that influence healthcare worker behaviors that result in injury. In addition, a number of issues relating to the postexposure management of occupational exposures with bloodborne pathogens need to be better understood.

Drug-induced liver disease 2004

PURPOSE OF REVIEW

To summarize the salient reviews, studies and case reports and series that dealt with clinical, pathological, methodological, and epidemiological descriptions of drug-induced liver disease in the calendar year 2004.

RECENT FINDINGS

While no new causes of drug-induced liver injury were reported for 2004, several new reports of previously recognized hepatotoxins, including herbal products, were published. These include the antiretroviral drugs for HIV and agents to manage tuberculosis. Acetaminophen (APAP) retained its preeminent position as the leading cause of drug-induced acute liver failure, currently accounting for nearly 50% of cases according to the latest figures from the U.S. Acute Liver Failure Study Group. Not surprisingly, APAP also heads the list of drugs and toxins leading to liver transplantation for acute hepatic failure. Efforts to reduce the number of cases of intentional APAP poisonings by restricting the number of tablets sold at any one time in the UK are ongoing, but the success of the program may be lessening, as was pointed out this year. The use of potentially hepatotoxic medications in patients with underlying liver disease was examined with the statins, and they emerged as a safe class for use in this setting.

SUMMARY

Given the apparent increasing incidence of acute liver failure attributable to APAP in the US, additional efforts are still needed to better define the risks associated with its use and to further reduce the incidence of severe liver injury from this widely used agent.

Antiretroviral-associated hepatotoxicity

The use of highly active antiretroviral therapy has dramatically reduced HIV-associated morbidity and mortality. As a result, patients are often being treated longer and with more complex medical regimens than ever before, increasing the risk for drug interactions and toxicities. In particular, hepatotoxicity caused by antiretroviral use has become an increasingly appreciated potential complication of drug treatment. All classes of antiretrovirals have been reported to induce liver enzyme abnormalities. However, certain antiretrovirals appear much more likely to be associated with drug-induced hepatotoxicity. The risk of antiretroviral-related hepatotoxicity may be associated with patient-specific risk factors, including pre-existing viral hepatitis, baseline elevated liver function test results, female gender, and substance abuse. In addition, complex drug-drug interactions may potentate the risk of antiretroviral-associated hepatotoxicity. Coinfection with hepatitis B or hepatitis C appears to increase the risk of antiretroviral-related hepatotoxicity.

Predisposition to nevirapine hypersensitivity associated with HLA-DRB1*0101 and abrogated by low CD4 T-cell counts

Genetic (human leukocyte antigen), disease-related and demographic risk factors for nevirapine reactions were examined in a nevirapine-exposed cohort. Cases involving combinations of hepatitis, fever or rash were associated with an interaction between HLA-DRB1*0101 and the percentage of CD4, whereas no associations were detected for isolated rash. These data suggest that HLA-DRB1*0101 and the CD4 status may determine susceptibility to nevirapine hypersensitivity, consistent with a CD4 T-cell-dependent immune response to nevirapine-specific antigens.

Pharmacogenetics of antiretroviral therapy: genetic variation of response and toxicity

The application of a pharmacogenetic approach to antiretroviral drug therapy represents a significant challenge, as treatment involves multiple drugs and drug classes with the potential for significant variability in drug–host, as well as drug–drug, interactions. However, despite this inherent complexity, considerable gains have been made in understanding how genetic factors influence the efficacy and toxicity of HIV therapy. In this review the available evidence regarding genetic variation in drug disposition will be examined, including the potential for relatively polymorphic drug-metabolizing enzymes (e.g., cytochrome P450 isoforms) and drug transporters (e.g., P-glycoprotein) to influence the disposition of HIV protease inhibitor and non-nucleoside reverse transcriptase inhibitor drugs. In addition, the role of genetic variation in determining the immune response to drug-specific antigens will be considered as a potentially significant determinant of susceptibility to idiosyncratic drug reactions (e.g., major histocompatibility complex alleles associated with abacavir hypersensitivity). The current and potential clinical utility of pharmacogenetic testing in HIV management will also be emphasized.