Pharmacokinetic/pharmacodynamic and time-to-event models of ribavirin-induced anaemia in chronic hepatitis C

Finding the right hazard function for time-to-event modeling: A tutorial and Shiny application

Parametric time-to-event analysis is an important pharmacometric method to predict the probability of an event up until a certain time as a function of covariates and/or drug exposure. Modeling is performed at the level of the hazard function describing the instantaneous rate of an event occurring at that timepoint. We give an overview of the parametric time-to-event analysis starting with graphical exploration by Kaplan-Meier plotting for the event data including censoring and nonparametric hazard estimators such as the kernel-based visual hazard comparison for the underlying hazard. The most common hazard functions including the exponential, Gompertz, Weibull, log-normal, log-logistic, and circadian functions are described in detail. A Shiny application was developed to graphically guide the modeler which of the most common hazard functions presents a similar shape compared to the data in order to guide which hazard functions to test in the parametric time-to-event analysis. For the chosen hazard function(s), the Shiny application can additionally be used to explore corresponding parameter values to inform on suitable initial estimates for parametric modeling as well as on possible covariate or treatment relationships to certain parameters. Moreover, it can be used for the dissemination of results as well as communication, training, and workshops on time-to-event analysis. By guiding the modeler on which functions and what parameter values to test and compare as well as to assist in dissemination, the Shiny application developed here greatly supports the modeler in complicated parametric time-to-event modeling.

Emergent Drug and Nutrition Interactions in COVID-19: A Comprehensive Narrative Review

Coronaviruses are a large family of viruses that are known to cause respiratory tract infections ranging from colds to more severe diseases, such as Middle East Respiratory Syndrome (MERS) and the Severe Acute Respiratory Syndrome (SARS). New Coronavirus Disease 2019 (COVID-19), which led to deaths as well as social and economic disruptions, is an ongoing worldwide pandemic caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Currently, there is no approved treatment for COVID-19. Hence, only supportive care has been approved by the World Health Organization (WHO) for now. Pharmacological agents used for the adjunctive treatment of COVID-19 following the current literature and clinical experiences include antiviral, anti-inflammatory, and anti-malaria drugs, and other traditional or untraditional treatments. However, it has been reported that the use of these drugs may have some negative effects and comorbidities. Moreover, the current data have indicated that the risk of drug-drug interactions may also be high in polypharmacy cases, especially in elderly people, some comorbidity situations, and intensive care unit (ICU) patients. It is highly possible that these situations can not only increase the risk of drug-drug interactions but also increase the risk of food/nutrition-drug interactions and affect the nutritional status. However, this issue has not yet been entirely discussed in the literature. In this review, current information on the possible mechanisms as well as pharmacokinetic and pharmacodynamic effects of some pharmacological agents used in the treatment of COVID-19 and/or their secondary interactions with nutrition were evaluated and some future directions were given.

COVID-19 outbreak: Challenges in pharmacotherapy based on pharmacokinetic and pharmacodynamic aspects of drug therapy in patients with moderate to severe infection

The new coronavirus (COVID-19) was first detected in Wuhan city of China in December 2019. Most patients infected with COVID-19 had clinical presentations of dry cough, fever, dyspnea, chest pain, fatigue and malaise, pneumonia, and bilateral infiltration in chest CT. Soon COVID-19 was spread around the world and became a pandemic. Now many patients around the world are suffering from this disease. Patients with predisposing diseases are highly prone to COVID-19 and manifesting severe infection especially with organ function damage such as acute respiratory distress syndrome, acute kidney injury, septic shock, ventilator-associated pneumonia, and death. Till now many drugs have been considered in the treatment of COVID-19 pneumonia, but pharmacotherapy in elderly patients and patients with pre-existing comorbidities is highly challenging. In this review, different potential drugs which have been considered in COVID-19 treatment have been discussed in detail. Also, challenges in the pharmacotherapy of COVID-19 pneumonia in patients with the underlying disease have been considered based on pharmacokinetic and pharmacodynamic aspects of these drugs.

Time-to-Event Modeling of Left- or Right-Censored Toxicity Data in Nonclinical Drug Toxicology

A time-to-event (TTE) model has been developed to characterize a histopathology toxicity that can only be detected at the time of animal sacrifice. The model of choice was a hazard model with a Weibull distribution and dose was a significant covariate. The diagnostic plots showed a satisfactory fit of the data, despite the high degree of left and right censoring. Comparison to a probabilistic logit model shows similar performance in describing the data with a slight underestimation of survival by the Logit model. However, the TTE model was found to be more predictive in extrapolating toxicity risk beyond the observation range of a truncated dataset. The diagnostic and comparison outcomes would suggest using the TTE approach as a first choice for characterizing short and long-term risk from nonclinical toxicity studies. However, further investigations are needed to explore the domain of application of this kind of approach in drug safety assessment.

Rapid CO breath test screening of drugs for protective effects on ribavirin-induced hemolysis in a rabbit model: a pilot study

Hemolytic anemia is a major side effect of ribavirin antiviral treatment for chronic hepatitis C. Ribavirin dose reduction may compromise the antiviral response and erythropoietin can take several weeks to alleviate anemia. The purpose of the present study was to screen potentially protective drugs against ribavirin-induced hemolytic anemia in a rabbit model, using our modified CO breath test for measuring erythrocyte (RBC) lifespan, the gold standard diagnostic index of hemolysis. Fifteen rabbits were divided randomly into five groups (N  =  3/group): one vehicle control group, one ribavirin (only)-treated (RBV) group, and three groups initially treated with ribavirin only, followed by a combination of ribavirin with prednisone (RBV  +  Pred), polyene phosphatidyl choline (RBV  +  PPC), or reduced glutathione (RBV  +  GSH). RBC lifespan was calculated from accumulated CO measured in a closed rebreath apparatus, blood volume measured by the Evan's blue dye (EBD) dilution test, and hemoglobin concentration data. The RBC lifespan was normal in the vehicle control group (44-60 d), but reduced significantly in all of the ribavirin-treated groups before the addition of screened drugs (17-35 d). RBC lifespan rebounded significantly with the addition of glutathione, but not with the addition of prednisone or polyene phosphatidyl choline. A similar overall drug effect pattern was seen in the hemoglobin concentration and reticulocyte count data. In conclusion, the results of this pilot study indicate that reduced glutathione can attenuate ribavirin-induced hemolytic anemia, and that the RBC lifespan measured with our modified rapid CO breath test is feasible and reliable for use in animal studies.

A Modified Carbon Monoxide Breath Test for Measuring Erythrocyte Lifespan in Small Animals

This study was to develop a CO breath test for RBC lifespan estimation of small animals. The ribavirin induced hemolysis rabbit models were placed individually in a closed rebreath cage and air samples were collected for measurement of CO concentration. RBC lifespan was calculated from accumulated CO, blood volume, and hemoglobin concentration data. RBC lifespan was determined in the same animals with the standard biotin-labeling method. RBC lifespan data obtained by the CO breath test method for control (CON, 49.0 ± 5.9 d) rabbits, rabbits given 10 mg/kg·d⁻¹ of ribavirin (RIB10, 31.0 ± 4.0 d), and rabbits given 20 mg/kg·d⁻¹ of ribavirin (RIB20, 25.0 ± 2.9 d) were statistically similar (all p > 0.05) to and linearly correlated (r = 0.96, p < 0.01) with the RBC lifespan data obtained for the same rabbits by the standard biotin-labeling method (CON, 51.0 ± 2.7 d; RIB10, 33.0 ± 1.3 d; and RIB20, 27.0 ± 0.8 d). The CO breath test method takes less than 3 h to complete, whereas the standard method requires at least several weeks. In conclusion, the CO breath test method provides a simple and rapid means of estimating RBC lifespan and is feasible for use with small animal models.

Modeling Ribavirin-Induced Anemia in Patients with Chronic Hepatitis C Virus

Ribavirin remains an important component of hepatitis C treatment in certain clinical scenarios, but it causes hemolytic anemia. A quantitative understanding of the ribavirin exposure-anemia relationship is important in dose individualization/optimization. We developed a model relating ribavirin triphosphate (RTP) exposure in red blood cells (RBCs), RBC lifespan, feedback regulation of RBC production when anemia occurs, and the resulting hemoglobin decline. Inosine triphosphatase (ITPA) and interleukin 28B (IL28B) genetics were found to be significant covariates. Clinical trial simulations predicted that anemia is least severe in IL28B non-CC (rs12979860, CT or TT), ITPA variant subjects, followed by IL28B non-CC, ITPA wild-type, IL28B CC, ITPA variant, and IL28B CC, ITPA wild-type subjects (most severe). Reducing the ribavirin dose from 1,200/1,000 mg to 800/600 mg could reduce the proportions of grade 2 anemia by about half. The resulting model framework will aid the development of dosing strategies that minimize the incidence of anemia in treatment regimens that include ribavirin.

Current and emerging strategies for the diagnosis, prevention and treatment of Lassa fever

ABSTRACT 

Lassa fever (LF) is a potentially fatal disease that affects an estimated 300,000–500,000 people in endemic areas of west Africa each year. Though past studies have identified fatality rates of 5–20% in patients suspected to have contracted Lassa virus (LASV), new studies using more precise clinical diagnoses and modern diagnostic assays show fatalities rates above 60% in acutely ill patients from endemic regions. Currently, there are no approved vaccines or therapeutics, and only one Comformité Européenne (CE) marked rapid immunodiagnostic for acute LASV infection. Therefore, preventing LASV transmission is the primary goal in endemic regions. Development of rapid immunodiagnostics and research into the efficacy of current treatment options continues toward saving lives in west Africa as well as creating a line of defense against the nefarious use of LASV in bioterrorism settings.

A formula to estimate the optimal dosage of ribavirin for the treatment of chronic hepatitis C: influence of ITPA polymorphisms

BACKGROUND

Greater cumulative exposure to ribavirin increases response to interferon-ribavirin combination therapy for hepatitis C but also induces more severe anaemia. Polymorphisms in the ITPA gene protect against ribavirin-induced anaemia. The maximum dosage of ribavirin that can be tolerated by patients with different ITPA polymorphisms remains unknown.

METHODS

We developed a mathematical model of haemoglobin (Hb) decline in patients undergoing combination therapy. Using it to analyse published patient data, we estimated the average erythrocyte lifespan in patients with different ITPA polymorphisms. Coupled with a previous population pharmacokinetic study, we derived a formula for predicting the optimal ribavirin dosage, D(opt), above which anaemia becomes intolerable (Hb<10 g/dl).

RESULTS

Our model provided good fits to patient data of ribavirin accumulation in erythrocytes and the ensuing Hb decline during therapy. With the current treatment protocol, the average erythrocyte lifespan was approximately 36 days in patients with wild-type ITPA activity, and approximately 43 days and 55 days, respectively, in patients with mild and moderate ITPA deficiency. Our model yielded a facile formula for estimating D(opt) given a patient's weight, creatinine clearance, pretreatment Hb and ITPA polymorphism. Patients with moderate ITPA deficiency are predicted to tolerate twice the ribavirin dosage as patients with wild-type ITPA.

CONCLUSIONS

Our formula for D(opt) presents an avenue for personalizing ribavirin dosage. By keeping anaemia tolerable, the predicted optimal dosage may improve adherence, reduce the need for drug monitoring, and increase response rates. Response rates may be increased further by the higher dosages recommended for patients with ITPA deficiency.

Virological response is associated with decline in hemoglobin concentration during pegylated interferon and ribavirin therapy in hepatitis C virus genotype 1

Anemia may increase the likelihood of achieving a sustained virological response (SVR) during pegylated interferon and ribavirin treatment of hepatitis C virus (HCV) infection. To determine whether hemoglobin decline is associated with SVR, we retrospectively evaluated the CHARIOT study of 871 treatment-naïve HCV genotype 1 patients. Anemia (serum hemoglobin <100 g/L) occurred in 137 (16%) patients, of whom only 14 (10%) received erythropoietin. Hemoglobin decline >30g/L from baseline occurred in 76% of patients overall, including 526 patients who did not become anemic. Virological responses were higher in anemic patients compared with those who did not develop anemia (end of treatment, 80% versus 65%, P = 0.003; SVR, 61% versus 50%, P = 0.02); these differences remained significant when patients receiving erythropoietin were excluded from analysis. SVR was also higher in patients with hemoglobin decline >30 g/L compared with patients without a similar decline. In multiple logistic regression analyses with treatment group and baseline characteristics, the odds ratio for SVR was 1.97 (95% confidence interval, 1.08-3.62) for anemia and 2.17 (95% confidence interval, 1.31-3.62) for hemoglobin decline >30 g/L. Patients who first developed a hemoglobin decline >30 g/L during weeks 5-12 and 13-48 were more likely to achieve SVR than those who first developed such changes in weeks 0-4 or who never experienced them.

CONCLUSION

Patients with HCV genotype 1 infection who develop anemia or experience a hemoglobin decline >30 g/L during weeks 5-48 of therapy achieve higher virological responses to pegylated interferon and ribavirin therapy that are unrelated to erythropoietin use.

Ribavirin-induced anemia in hepatitis C virus patients undergoing combination therapy

The current standard of care for hepatitis C virus (HCV) infection – combination therapy with pegylated interferon and ribavirin – elicits sustained responses in only ∼50% of the patients treated. No alternatives exist for patients who do not respond to combination therapy. Addition of ribavirin substantially improves response rates to interferon and lowers relapse rates following the cessation of therapy, suggesting that increasing ribavirin exposure may further improve treatment response. A key limitation, however, is the toxic side-effect of ribavirin, hemolytic anemia, which often necessitates a reduction of ribavirin dosage and compromises treatment response. Maximizing treatment response thus requires striking a balance between the antiviral and hemolytic activities of ribavirin. Current models of viral kinetics describe the enhancement of treatment response due to ribavirin. Ribavirin-induced anemia, however, remains poorly understood and precludes rational optimization of combination therapy. Here, we develop a new mathematical model of the population dynamics of erythrocytes that quantitatively describes ribavirin-induced anemia in HCV patients. Based on the assumption that ribavirin accumulation decreases erythrocyte lifespan in a dose-dependent manner, model predictions capture several independent experimental observations of the accumulation of ribavirin in erythrocytes and the resulting decline of hemoglobin in HCV patients undergoing combination therapy, estimate the reduced erythrocyte lifespan during therapy, and describe inter-patient variations in the severity of ribavirin-induced anemia. Further, model predictions estimate the threshold ribavirin exposure beyond which anemia becomes intolerable and suggest guidelines for the usage of growth hormones, such as erythropoietin, that stimulate erythrocyte production and avert the reduction of ribavirin dosage, thereby improving treatment response. Our model thus facilitates, in conjunction with models of viral kinetics, the rational identification of treatment protocols that maximize treatment response while curtailing side effects.

The treatment of HCV infection poses a major global health-care challenge today. The current standard of care, combination therapy with interferon and ribavirin, works in only about half of the patients treated. Because no alternatives are available yet for patients in whom combination therapy fails, identifying ways to improve response to combination therapy is critical. Increasing exposure to ribavirin does improve response but is associated with the severe side-effect, anemia. One way to maximize treatment response therefore is to increase ribavirin exposure to levels just below where anemia becomes intolerable. A second way is to supplement combination therapy with growth hormones, such as erythropoietin, that increase the production of red blood cells (erythrocytes) and compensate for ribavirin-induced anemia. Rational optimization of combination therapy thus relies on a quantitative description of ribavirin-induced anemia, which is currently lacking. Here, we develop a model of the population dynamics of erythrocytes in individuals exposed to ribavirin that quantitatively describes ribavirin-induced anemia. Model predictions capture several independent observations of ribavirin-induced anemia in HCV patients undergoing combination therapy, estimate the threshold ribavirin exposure beyond which anemia becomes intolerable, suggest guidelines for the usage of growth hormones, and facilitate rational optimization of therapy.

Review of the literature and proposed guidelines for the use of oral ribavirin as postexposure prophylaxis for Lassa fever

Lassa fever is an acute viral hemorrhagic illness; the virus is endemic in West Africa and also of concern with regard to bioterrorism. Transmission of Lassa virus between humans may occur through direct contact with infected blood or bodily secretions. Oral administration of the antiviral drug ribavirin is often considered for postexposure prophylaxis, but no systematically collected data or uniform guidelines exist for this indication. Furthermore, the relatively low secondary attack rates for Lassa fever, the restriction of the area of endemicity to West Africa, and the infrequency of high-risk exposures make it unlikely that controlled prospective efficacy trials will ever be possible. Recommendations for postexposure use of ribavirin can therefore be made only on the basis of a thorough understanding and logical extrapolation of existing data. Here, we review the pertinent issues and propose guidelines based on extensive review of the literature, as well as our experience in this field. We recommend oral ribavirin postexposure prophylaxis for Lassa fever exclusively for definitive high-risk exposures. These guidelines may also serve for exposure to other hemorrhagic fever viruses susceptible to ribavirin.

Role of ribavirin in HCV treatment response: now and in the future

IMPORTANCE OF THE FIELD

Ribavirin is a broad spectrum antiviral agent that is used with pegylated IFN (Peg-IFN) for HCV treatment. Ribavirin does not significantly reduce HCV viral load when used alone but increases rates of sustained virologic response (SVR) when combined with Peg-IFN. HCV genotype 1 infected patients require higher doses of ribavirin administered for a longer duration of time versus HCV genotypes 2 and 3 patients who respond effectively to Peg-IFN with lower doses of ribavirin and shorter duration of therapy. Higher serum concentrations of ribavirin are associated with higher response rates but also higher rates of hemolytic anemia which is a dose limiting side effect. Alternatives to current therapy are under clinical evaluation.

AREAS COVERED IN THIS REVIEW

Systematic literature review of ribavirin use in HCV patients from 1995 to 2009 was conducted.

WHAT THE READER WILL GAIN

To review the efficacy and safety of ribavirin in current HCV treatment and in new therapies in Phase III clinical trials.

TAKE HOME MESSAGE

Ribavirin is a drug which is essential to produce higher SVR rates both with Peg-IFN and HCV protease inhibitors currently in Phase III clinical trials. Thus, ribavirin is and will remain an important drug to achieving higher SVR rates in HCV infected persons.

Evaluation of drugs in pediatrics using K-PD models: perspectives

Some pharmacodynamic (PD) models, called K-PD models, have been developed for the description of drug action kinetics in the absence of drug concentration measurements. Because blood samples for drug measurements are not needed, these models may be very useful in pediatric studies, by reducing their invasiveness. In addition, a number of PD measurements are also non-invasive and specific devices exist for measures in children. Therefore, the kinetics of drug action may be characterized with minimal invasiveness. A brief description of the key features of these models is given, and a number of examples of application are presented. K-PD models are expected to be most useful when the drug kinetics is simple (i.e. when the one-compartment model is a reasonable description), or when the response kinetics is slow compared with drug kinetics. K-PD models have already demonstrated their usefulness in animal and adult studies. They are very attractive for pediatric studies and they should facilitate the assessment of drug efficacy and safety.

Ribavirin in the treatment of chronic hepatitis C

BACKGROUND AND AIM

Current practice guidelines recommend that individuals chronically infected with the hepatitis C virus (HCV) be treated with pegylated interferon plus ribavirin. Ribavirin, however, is associated with serious adverse events (AE), especially anemia. We review its mechanism of action, its importance in treating chronic hepatitis C (CHC) patients, the AE associated with its use, and techniques used to lessen these AE.

METHODS

Medline searches were performed using the keywords ribavirin and hepatitis, together with the keywords mechanism, anemia, liver transplant, renal function, pharmacokinetics, and dose reduction. Searches of abstracts of recent Digestive Diseases Week, American Association for the Study of Liver Diseases, and European Association for the Study of Liver Diseases meetings were also performed.

RESULTS

Ribavirin may be effective in treating CHC by affecting the virus or the host; for example by inducing viral mutations, blocking cellular enzymes, or affecting the host immune response. Although the pegylated interferons are the primary drugs used to treat CHC, a combination with ribavirin is more effective than pegylated interferon alone. Ribavirin-associated AE may be lessened by ribavirin dose reductions and by maintenance of the hematocrit.

CONCLUSIONS

Treatments of ribavirin toxicities, especially anemia, can allow patients to continue full-dose combination therapy with peginterferon and ribavirin, enhancing their probability of attaining a sustained virologic response (SVR). Treatment of CHC should be tailored to individual patients, especially those with renal dysfunction, and should include agents that treat the side-effects of CHC treatment. Monitoring of plasma ribavirin concentrations during treatment may help in the future.

Pharmacokinetic evaluation of the effects of ribavirin on zidovudine triphosphate formation: ACTG 5092s Study Team

OBJECTIVES

Ribavirin (RBV) is used for the treatment of hepatitis C virus (HCV) infection in subjects with HIV-1 infection who may require antiretroviral treatment (ART) with nucleoside reverse transcriptase inhibitors including zidovudine (ZDV). We sought to investigate the potential antagonism between RBV and ZDV by evaluating the impact of RBV on the formation of intracellular ZDV triphosphate (TP) in HIV-infected patients receiving ZDV who were treated for HCV infection.

METHODS

Serial plasma and intracellular ZDV TP pharmacokinetics (PK) were determined in 14 subjects at entry (within 2 weeks prior to RBV administration) and at 8 weeks following initiation of RBV. Intracellular ZDV TP in peripheral blood mononuclear cells (PBMC) was quantified by a validated cartridge/liquid chromatography/tandem mass spectrometry method. PK exposure was estimated from the steady-state area under the concentration vs time curve (AUC(0-12 h)) in plasma and PBMC.

RESULTS

Ribavirin did not have a statistically significant impact on ZDV TP AUC(0-12 h), plasma ZDV AUC(0-12 h) or the ratio of ZDV TP AUC(0-12 h) to plasma ZDV AUC(0-12 h), although there was a trend towards an increase post-RBV ratio compared with pre-RBV. There was extensive variability in the ZDV TP AUC(0-12 h).

CONCLUSIONS

Ribavirin did not inhibit formation of ZDV TP in PBMC in 14 patients receiving ZDV as part of ART and RBV-based HCV therapy for 8 weeks. These results are consistent with those of a previously published limited study in seven subjects. These PK findings should be weighed carefully against emerging clinical reports of significant anaemia associated with combination ZDV and high-dose RBV therapy.

Virological response and safety outcomes in therapy-nai ve patients treated for chronic hepatitis C with taribavirin or ribavirin in combination with pegylated interferon alfa-2a: a randomized, phase 2 study

BACKGROUND/AIMS

Pegylated interferon plus ribavirin can cause dose-limiting anemia. Taribavirin, a ribavirin prodrug, has shown a lower incidence of anemia. We sought to determine the efficacy and safety of taribavirin vs. ribavirin combined with pegylated interferon in patients with chronic hepatitis C (CHC).

METHODS

This phase 2 open-label study randomized 180 patients with CHC to receive pegylated interferon alfa-2a 180 microg/week plus taribavirin 800, 1200 or 1600 mg QD or ribavirin 1000 or 1200 mg QD. Efficacy variables included proportions of patients with undetectable serum HCV RNA levels at end of treatment and after a 24-week follow-up.

RESULTS

The proportions of patients with undetectable HCV RNA at 12 weeks did not differ significantly between taribavirin (38%, 42%, and 49% for the 800, 1200, and 1600 mg groups) and ribavirin (49%). The highest proportion of patients with undetectable HCV RNA at end of treatment and at follow-up occurred in both the taribavirin 1200mg QD (63% and 37%) and ribavirin groups (62% and 44%). SVR rates were 23%, 37% and 29% for taribavirin and 44% for ribavirin. Fewer patients on any dose of taribavirin had severe anemia (hemoglobin <10 g/dL) than on ribavirin (6/135 [4%] vs. 12/45 [27%]).

CONCLUSIONS

Given with interferon, taribavirin produced SVR rates comparable to those of ribavirin, with a lower occurrence of anemia.

Therapeutic issues in HIV/HCV-coinfected patients

The importance of treating hepatitis C virus (HCV)-associated morbidities in a growing population of patients coinfected with human immunodeficiency virus (HIV) has increased since the introduction of highly active antiretroviral therapy. As a result, investigative attention is turning to HCV-related liver disease and treatment-associated issues in coinfection. HIV/HCV-coinfected patients have higher HCV RNA loads and show more rapid progression of fibrosis than do monoinfected patients. Combination therapy with pegylated interferon plus ribavirin (RBV) is the standard of care for HCV in coinfected patients. Therapy slows fibrosis progression, but toxicity prevents identification of the most effective RBV dose. Coinfected patients have about a threefold greater risk of antiretroviral therapy-associated hepatotoxicity than patients with HIV only. Other challenges include anaemia, mitochondrial toxicity, drug-drug interactions and leucopenia. Thus, chronic hepatitis C should be treated in HIV/HCV-coinfected patients, but steps must be taken to prevent and treat potential toxicities. The first European Consensus Conference on the Treatment of Chronic Hepatitis B and C in HIV Co-infected Patients was held March 2005 in Paris to address these issues. This article reviews the peer-reviewed literature and expert opinion published from 1990 to 2005, and compares results with presentations and recommendations from the Consensus Conference to best present current issues in coinfection.

A kinetic-pharmacodynamic model for clinical trial simulation of antidepressant action: Application to clomipramine–lithium interaction

A generic kinetic-pharmacodynamic (K-PD) model to describe the response to treatment assessed by a clinical score for depressed patients treated by antidepressants alone or combined with a drug that shortens the lag-time before effect was developed. The aims of this study were: (1) to verify model's ability to characterize clinical data, (2) to evaluate several statistics to summarize the clinical effect, (3) to compare the analysis based on these statistics to the conventional intent-to-treat analysis and (4) to determine the optimal dates of clinical assessment. The population K-PD model was fitted to the individual data from a randomized clinical trial assessing the efficacies of clomipramine and placebo or clomipramine and lithium to treat major depression in 141 patients. The K-PD model was able to fit the individual data even in the case of oscillating score profiles. The interindividual coefficient of variation of the model parameters ranged from 33 to 161%. The statistical analysis based on the secondary parameters yielded conclusions comparable to those of the conventional intent-to-treat analysis. The population model was then used for a clinical trial simulation. According to the simulation, the most sensitive summary statistics for detecting a difference between lithium and placebo were the fractional reduction of depression and the proportion of responders. The optimal dates to assess these parameters were day 9 and 11 respectively. The K-PD model might serve as a tool for clinical trial planning in the field of research on antidepressants and their facilitators.

Depression, anemia and health-related quality of life in chronic hepatitis C

BACKGROUND/AIMS

Hepatitis C (HCV) infected patients have significant health-related quality of life (HRQL) impairment which worsens during anti-viral therapy. Our aim was to examine the association of HRQL with treatment-induced depression and anemia.

METHODS

Two hundred and seventy-one HCV patients who received pegylated interferon alfa 2b and ribavirin were included. Data on HRQL, depressive symptoms, laboratory values and socio-demographic characteristics were collected.

RESULTS

Mean age was 47.1+/-6.5, 69% were male, and 73% were White. HCV patients' HRQL declined during anti-viral therapy but returned to or exceeded baseline levels within 24 weeks of completion. Anemia and depression were both associated with HRQL impairment. The effects of depression on HRQL were strong; once depression scores were included other factors were no longer significant. Patients' depressive symptoms tended to increase during the initial half of treatment regimen. Those with higher body mass index (BMI), cirrhosis, and women reported more HRQL impairments. HRQL scales were generally not associated with alcohol abuse, age, race, ALT and HCV RNA levels.

CONCLUSIONS

Anti-viral therapy for HCV is associated with diminished HRQL. Although anemia and depression were associated with this impairment, depression was the most consistent predictor. Future studies are needed to see whether proactive management of these side effects can improve patients' HRQL and the efficacy of antiviral therapy for hepatitis C.