High-performance liquid chromatographic determination of ribavirin in whole blood to assess disposition in erythrocytes

RGD-coated polymeric microbubbles promote ultrasound-mediated drug delivery in an inflamed endothelium-pericyte co-culture model of the blood-brain barrier

Drug delivery to central nervous pathologies is compromised by the blood-brain barrier (BBB). A clinically explored strategy to promote drug delivery across the BBB is sonopermeation, which relies on the combined use of ultrasound (US) and microbubbles (MB) to induce temporally and spatially controlled opening of the BBB. We developed an advanced in vitro BBB model to study the impact of sonopermeation on the delivery of the prototypic polymeric drug carrier pHPMA as a larger molecule and the small molecule antiviral drug ribavirin. This was done under standard and under inflammatory conditions, employing both untargeted and RGD peptide-coated MB. The BBB model is based on human cerebral capillary endothelial cells and human placental pericytes, which are co-cultivated in transwell inserts and which present with proper transendothelial electrical resistance (TEER). Sonopermeation induced a significant decrease in TEER values and facilitated the trans-BBB delivery of fluorescently labeled pHPMA (Atto488-pHPMA). To study drug delivery under inflamed endothelial conditions, which are typical for e.g. tumors, neurodegenerative diseases and CNS infections, tumor necrosis factor (TNF) was employed to induce inflammation in the BBB model. RGD-coated MB bound to and permeabilized the inflamed endothelium-pericyte co-culture model, and potently improved Atto488-pHPMA and ribavirin delivery. Taken together, our work combines in vitro BBB bioengineering with MB-mediated drug delivery enhancement, thereby providing a framework for future studies on optimization of US-mediated drug delivery to the brain.

Separate Evaluation of Fraction Absorbed and Intestinal Availability after Oral Administration of Drugs Based on the Measurement of Portal and Systemic Plasma Concentrations and Luminal Concentration

There are several experimental methods to estimate the product of the fraction absorbed (Fa) and intestinal availability (Fg) in vivo after oral administration of drugs. Metabolic enzyme inhibitors are typically used to separate Fg from Fa·Fg. Since Fa·Fg can be regarded as Fa under metabolism-inhibited conditions, Fg can be isolated by dividing Fa·Fg by Fa. However, if the inhibition of intestinal metabolism is insufficient, Fa is overestimated, which results in an underestimation of Fg compared to the actual value. In this study, to avoid this problem, an experimental method for the separate estimation of Fa and Fg in rats without utilizing metabolic enzyme inhibitors was established. Buspirone, a CYP3A substrate, and ribavirin, a substrate of purine nucleoside phosphorylase and adenosine kinase, were selected as models. Following oral administration of the drugs with fluorescein isothiocyanate dextran 4000 (FD-4, an unabsorbable marker), Fa·Fg was pharmacokinetically calculated from portal and systemic plasma concentration-time profiles of model drugs and Fa was calculated from the difference in the ileal concentration profiles of the drugs and FD-4. Fg was evaluated by dividing Fa·Fg by Fa. Following oral administration, buspirone was not detected in any segment of the small intestine, indicating that the administered buspirone was completely absorbed. In addition, buspirone was extensively metabolized in enterocytes (Fg = 20.1). Ribavirin was primarily absorbed in the upper segment of the small intestine, and 64.4% of the ribavirin was absorbed before it reached the ileum. In addition, it was revealed that ribavirin was metabolized more extensively in the intestine than in the liver. Our method may be effective in quantitatively assessing Fa and Fg in vivo, which can help in the formulation design and prediction of drug-drug interactions.

Precision Medicine: Determination of Ribavirin Urinary Metabolites in Relation to Drug Adverse Effects in HCV Patients

The most commonly used antiviral treatment against hepatitis C virus is a combination of direct-acting antivirals (DAAs) and ribavirin (RBV), which leads to a shortened duration of therapy and a sustained virologic response until 98%. Nonetheless, several dose-related side effects of RBV could limit its applications. This study aims to measure the urinary concentration of RBV and its main metabolites in order to evaluate the drug metabolism ability of HCV patients and to evaluate the adverse effects, such as anemia, with respect to RBV metabolite levels. RBV and its proactive and inactive metabolites were identified and quantified in the urine of 17 HCV males with severe liver fibrosis using proton nuclear magnetic resonance (¹H-NMR) at the fourth week (TW4) and at the twelfth week of treatment (EOT). Four prodrug urinary metabolites, including RBV, were identified and three of them were quantified. At both the TW4 and EOT stages, six HCV patients were found to maintain high concentrations of RBV, while another six patients maintained a high level of RBV proactive metabolites, likely due to nucleosidase activity. Furthermore, a negative correlation between the reduction in hemoglobin (Hb) and proactive forms was observed, according to RBV-triphosphate accumulation causing the hemolysis. These findings represent a proof of concept regarding tailoring the drug dose in relation to the specific metabolic ability of the individual, as expected by the precision medicine approach.

A randomized, placebo-controlled study to evaluate safety and pharmacokinetics of inhaled ribavirin

Ribavirin is an inosine monophosphate dehydrogenase inhibitor. Studies suggest ribavirin aerosol could be a safe and efficacious treatment option in the fight against coronaviruses. However, current treatment is long (12-18 h per day, 3-7 days), limiting clinical utility. A reduction in treatment time would reduce treatment burden. We aimed to evaluate safety and pharmacokinetics (PK) of four, single-dose regimens of ribavirin aerosol in healthy volunteers. Thirty-two subjects were randomized, to four cohorts of aerosolized ribavirin (active) or placebo. Cohort 1 received 50 mg/ml ribavirin/placebo (10 ml total volume); cohort 2, 50 mg/ml ribavirin/placebo (20 ml total volume); cohort 3, 100 mg/ml ribavirin/placebo (10 ml total volume); and cohort 4, 100 mg/ml ribavirin/placebo (20 ml total volume). Intense safety monitoring and PK sampling took place on days 1, 2, 3, and 40. Subjects were (mean ± SD, active vs. placebo) aged 57 ± 4.5 vs. 60 ± 2.5 years; 83% vs. 88% were female; and 75% vs. 50% were Caucasian. Some 12.5% (3/24) and 25% (2/8) experienced at least one treatment-emergent adverse event (TEAE) (two moderate; five mild) in the active and placebo groups, respectively. No clinically significant safety concerns were reported. Mean maximum observed concentration (C_max ) and area under the curve (AUC) values were higher in cohort 4, whereas cohorts 2 and 3 showed similar PK values. Ribavirin absorption reached C_max within 2 h across cohorts. Four single-dose regimens of ribavirin aerosol demonstrated systemic exposure with minimal systemic effects. Results support continued clinical development of ribavirin aerosol as a treatment option in patients with coronaviruses.

Antiviral Effects of ABMA and DABMA against Influenza Virus In Vitro and In Vivo via Regulating the Endolysosomal Pathway and Autophagy

Influenza virus is an acute and highly contagious respiratory pathogen that causes great concern to public health and for which there is a need for extensive drug discovery. The small chemical compound ABMA and its analog DABMA, containing an adamantane or a dimethyl-adamantane group, respectively, have been demonstrated to inhibit multiple toxins (diphtheria toxin, Clostridium difficile toxin B, Clostridium sordellii lethal toxin) and viruses (Ebola, rabies virus, HSV-2) by acting on the host’s vesicle trafficking. Here, we showed that ABMA and DABMA have antiviral effects against both amantadine-sensitive influenza virus subtypes (H1N1 and H3N2), amantadine-resistant subtypes (H3N2), and influenza B virus with EC₅₀ values ranging from 2.83 to 7.36 µM (ABMA) and 1.82 to 6.73 µM (DABMA), respectively. ABMA and DABMA inhibited the replication of influenza virus genomic RNA and protein synthesis by interfering with the entry stage of the virus. Molecular docking evaluation together with activity against amantadine-resistant influenza virus strains suggested that ABMA and DABMA were not acting as M2 ion channel blockers. Subsequently, we found that early internalized H1N1 virions were retained in accumulated late endosome compartments after ABMA treatment. Additionally, ABMA disrupted the early stages of the H1N1 life cycle or viral RNA synthesis by interfering with autophagy. ABMA and DABMA protected mice from an intranasal H1N1 challenge with an improved survival rate of 67%. The present study suggests that ABMA and DABMA are potential antiviral leads for the development of a host-directed treatment against influenza virus infection.

Validated RP-HPLC Method for Simultaneous Determination of Ribavirin, Sofosbuvir and Daclatasvir in Human Plasma: A Treatment Protocol Administered to HCV Patients in Egypt

Egypt has the highest prevalence of hepatitis C virus (HCV) in the world thus it launched a national program for eliminating HCV aiming to treat 300,000 HCV patients per year. Three anti-HCV co-administered drugs; ribavirin (RBV), sofosbuvir (SF) daclatasvir (DAC) were simultaneously determined in human plasma by a validated, simple and sensitive RP-HPLC method using propyl paraben as an internal standard. Liquid-liquid extraction using ethyl acetate was used for samples extraction. Chromatographic separation was achieved on Scharlau® C18 column (250 × 4.6 mm2, 5 μm). Gradient elution was employed with a mobile phase mixture of water and acetonitrile at a flow rate 1 mL/min. UV detection using photodiode array detector was carried out at 207, 260 and 312 nm for RBV, SF and DAC, respectively. Method validation was performed according to the FDA guidelines for bioanalytical method validation. The calibration curves were linear over the ranges (0.5-80, 0.1-40 and 0.5-80 μg/mL) with average recoveries (100.64-108.28%, 98.48-105.91% and 97.68-101.38%) for RBV, SF and DAC, respectively. The intra-day and inter-day precision and accuracy results were within the acceptable limits. Stability assays revealed that the three studied analytes were stable during sample storage, preparation and injection. The method can be successfully applied in routine analysis of plasma of HCV patients treated with this combination therapy which aids in therapeutic drug monitoring and patients' follow-up especially in Egypt and other developing countries fighting HCV.

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Ribavirin in combination with pegylated interferon alpha is the current treatment for chronic hepatitis C (HCV). Ribavirin presents a wide inter-individual pharmacokinetic variability and adequate exposure seems crucial for achieving sustained virologic response. Severe anaemia frequently occurred under ribavirin treatment and is a dose-dependent limiting side effect. Several studies have been carried out in HVC-infected or HIV-HCV co-infected patients to evaluate the pharmacokinetic-pharmacodynamic relationships of ribavirin. Achievement of a sustained virologic response, defined as undetectable HCV-RNA six months after the end of treatment, have been significantly associated with ribavirin concentration. A cut-off for the trough concentration of ribavirin ranging between 2-3μg/ml at week 4 has been proposed. A significant correlation has also been reported between ribavirin concentration and the extent of haemoglobin decline. A ribavirin concentration>2μg/ml is significantly associated to an increase risk of severe anaemia. Non randomized studies have shown that therapeutic drug monitoring of ribavirin improve the management of therapeutic response and haematologic toxicity. Therefore, the level of evidence of the therapeutic drug monitoring of ribavirin is recommended.

Determination of ribavirin in chicken muscle by quick, easy, cheap, effective, rugged and safe method and liquid chromatography-tandem mass spectrometry

A new analytical method for the determination of ribavirin in chicken muscle using a QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method and liquid chromatography-tandem mass spectrometry (LC-MS-MS) was developed and validated. Samples were extracted with acidified methanol (methanol:acetic acid, 99:1, v/v). The extract was further purified by QuEChERS method using primary-secondary amine (PSA) and C18. Finally, the extract was dried by nitrogen under 45°C and reconstituted in water. The separation was performed on a Hypercarb analytical column under a gradient elution. The mobile phase was composed of water buffered with ammonium acetate (2.0mM) and acetonitrile. The proposed method was validated according to the European Commission Decision 2002/657/EC. The values of the decision limit (CCα) and the detection capability (CCβ) were 1.1 and 1.5μg/kg, respectively. The mean recoveries of ribavirin ranged from 94.2% to 99.2%. The repeatability (expressed as coefficient of variation, CVr) of the method ranged from 4.5% to 4.9% and the reproducibility (CVR) of the method ranged from 4.8% to 5.4%. The method is demonstrated to be suitable for the determination of ribavirin in chicken muscle in conformity with the current EU performance requirements through validation. The total time required for the analysis of one sample, including sample preparation, was about 45min.

UHPLC-MS/MS method with automated on-line solid phase extraction for the quantification of entecavir in peripheral blood mononuclear cells of HBV+ patients

To date five nucleoside analogs are used in the treatment of chronic hepatitis B: among these, entecavir is the most used. Nevertheless a few information about its distribution in tissues is currently known. Since the determination of entecavir disposition in the hepatocytes is impracticable because of its invasiveness, the quantification in an "easier-to-obtain" cellular model could be a good choice. In this work, we developed and validated an ultra performance liquid chromatography-tandem mass spectrometry assay based on an automated on-line SPE, to quantify entecavir concentrations in peripheral blood mononucleated cells (PBMCs), in both its phosphorylated and un-phosphorylated forms. To achieve this, each PBMC isolate was divided in two aliquots, one was treated with acid phosphatase to convert entecavir phosphorylated metabolites into free form, the other one was not-treated. Standards and quality controls were prepared in PBMCs, isolated from healthy donors, and underwent the same process. 20 μL of the resulting solutions were injected in the on-line SPE system. Thymidine was used as internal standard. Calibration curves fitted a linear model for entecavir levels in a range from 0.039 ng to 5 ng (mean r(2)=0.998). Accuracy, intra-day and inter-day precision of the method fitted FDA guidelines recommendations. Moreover, recovery was consistent and matrix effect resulted low and reproducible. We tested this method by monitoring entecavir concentrations in PBMCs from 28HBV mono-infected patients, confirming its reliability and suitability for the evaluation of intracellular entecavir penetration.

Synthesis and Evaluation of Bile Acid-Ribavirin Conjugates as Prodrugs to Target the Liver

Ribavirin is used to treat hepatitis C but causes serious hemolytic anemia. The objective of the study was to develop a ribavirin prodrug to achieve liver-specific drug delivery and to reduce its off-target effect in red blood cells (RBCs). The approach aimed to target the human sodium taurocholate cotransporting polypeptide (NTCP), which is a bile acid transporter predominately expressed in the liver. Six prodrugs with ribavirin conjugation at C-3 or C-24 of the bile acids were synthesized. In vitro uptake studies indicated that all six prodrugs were NTCP substrates. Metabolic studies in vitro indicated that ribavirin-l-Val-glycochenodeoxycholic acid (GCDCA) was able to release ribavirin in the mouse liver S9 fraction. Additionally, in vitro studies showed that ribavirin in RBC was reduced by 16.7-fold from prodrug compared with parent drug incubation. Moreover, almost no prodrug was present in RBC. In vivo study in mice also showed that ribavirin-l-Val-GCDCA could provide almost the same ribavirin exposure in the liver as ribavirin administration, but with about 1.8-fold less exposure of ribavirin in RBC, plasma, and kidney. Overall, the study suggested that ribavirin-l-Val-GCDCA has the potential to achieve ribavirin-specific liver delivery.

Measurement of intracellular ribavirin mono-, di- and triphosphate using solid phase extraction and LC-MS/MS quantification

Ribavirin (RBV) is a nucleoside analog used to treat a variety of DNA and RNA viruses. RBV undergoes intracellular phosphorylation to a mono- (MP), di- (DP), and triphosphate (TP). The phosphorylated forms have been associated with the mechanisms of antiviral effect observed in vitro, but the intracellular pharmacology of the drug has not been well characterized in vivo. A highly sensitive LC-MS/MS method was developed and validated for the determination of intracellular RBV MP, DP, and TP in multiple cell matrix types. For this method, the individual MP, DP, and TP fractions were isolated from lysed intracellular matrix using strong anion exchange solid phase extraction, dephosphorylated to parent RBV, desalted and concentrated and quantified using LC-MS/MS. The method utilized a stable labeled internal standard (RBV-(13)C5) which facilitated accuracy (% deviation within ±15%) and precision (coefficient of variation of ≤15%). The quantifiable linear range for the assay was 0.50 to 200 pmol/sample. The method was applied to the measurement of RBV MP, DP, and TP in human peripheral blood mononuclear cells (PBMC), red blood cells (RBC), and dried blood spot (DBS) samples obtained from patients taking RBV for the treatment of chronic Hepatitis C virus infection.

Using pharmacokinetic and viral kinetic modeling to estimate the antiviral effectiveness of telaprevir, boceprevir, and pegylated interferon during triple therapy in treatment-experienced hepatitis C virus-infected cirrhotic patients

Triple therapy combining a protease inhibitor (PI) (telaprevir or boceprevir), pegylated interferon (PEG-IFN), and ribavirin (RBV) has dramatically increased the chance of eradicating hepatitis C virus (HCV). However, the efficacy of this treatment remains suboptimal in cirrhotic treatment-experienced patients. Here, we aimed to better understand the origin of this impaired response by estimating the antiviral effectiveness of each drug. Fifteen HCV genotype 1-infected patients with compensated cirrhosis, who were nonresponders to prior PEG-IFN/RBV therapy, were enrolled in a nonrandomized study. HCV RNA and concentrations of PIs, PEG-IFN, and RBV were frequently assessed in the first 12 weeks of treatment and were analyzed using a pharmacokinetic/viral kinetic model. The two PIs achieved similar levels of molar concentrations (P=0.5), but there was a significant difference in the 50% effective concentrations (EC50) (P=0.008), leading to greater effectiveness for telaprevir than for boceprevir in blocking viral production (99.8% versus 99.0%, respectively, P=0.002). In all patients, the antiviral effectiveness of PEG-IFN was modest (43.4%), and there was no significant contribution of RBV exposure to the total antiviral effectiveness. The second phase of viral decline, which is attributed to the loss rate of infected cells, was slow (0.19 day(-1)) and was higher in patients who subsequently eradicated HCV (P=0.03). The two PIs achieved high levels of antiviral effectiveness. However, the suboptimal antiviral effectiveness of PEG-IFN/RBV and the low loss of infected cells suggest that a longer treatment duration might be needed in cirrhotic treatment-experienced patients and that a future IFN-free regimen may be particularly beneficial in these patients.

Development and validation of a useful UPLC-MS/MS method for quantification of total and phosphorylated-ribavirin in peripheral blood mononuclear cells of HCV+ patients

The current standard-of-care therapy in HCV consists in ribavirin (RBV) plus pegylated-interferon-α 2a or 2b and, for HCV-1 infected patients, also directly acting antivirals (DAAs). Despite the increase in the number of patients who reach sustained virological response (SVR) for HCV-1, a great inter-individual variability in the response to therapy remains. Whether new drugs are available in combination with RBV and Peg-IFN for HCV-1, the treatment of the other viral genotypes remains the same: this issue highlights the lasting importance of RBV and Peg-IFN in anti-HCV treatment. Moreover, a strong limiting factor to the usefulness of anti-HCV treatment remains the occurrence of adverse events, first of all hemolytic anemia, which have increased with the addition of DAAs, but is mainly an RBV-dependent effect. For these reasons, the monitoring of RBV exposure in the various compartments should be important. Since the routinely determination of RBV in the target cells as the hepatocytes is impracticable for of its invasiveness, the quantification in easier to obtain cells could be a good choice. In this work, we developed and validated an ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) assay method to quantify RBV concentrations in peripheral blood mononucleated cells (PBMCs). QCs were prepared with RBV and RBV-monophosphate (RMP). Each sample was divided into two aliquots, which undergone the same extraction procedure: one was treated with acid phosphatase to convert RBV phosphorylated metabolites into free RBV, the other one was not-treated. The extracts were analyzed with reverse-phase column with UPLC-MS/MS. Calibration curves fitted a least squares model (weighed 1/X) for ribavirin levels in a range from 0.1 ng to 200 ng (mean r(2)=0.9993). Accuracy, intra-day and inter-day precision of the methods were in accordance with FDA guidelines. Moreover, phosphorylated QCs were used to assess the correct determination of total RBV concentration. We tested this method by monitoring RBV concentrations in PBMCs from 20 HCV+ patients, receiving alpha interferon-plus RBV combination therapy. This method showed to be reliable, precise, accurate and suitable for evaluation of intracellular RBV concentrations.

Utility of high-resolution accurate MS to eliminate interferences in the bioanalysis of ribavirin and its phosphate metabolites

BACKGROUND

The polar nucleoside drug ribavirin (RBV) combined with IFN-α is a front-line treatment for chronic hepatitis C virus infection. RBV acts as a prodrug and exerts its broad antiviral activity primarily through its active phosphorylated metabolite ribavirin 5´-triphosphate (RTP), and also possibly through ribavirin 5´-monophosphate (RMP). To study RBV transport, diffusion, metabolic clearance and its impact on drug-metabolizing enzymes, a LC-MS method is needed to simultaneously quantify RBV and its phosphorylated metabolites (RTP, ribavirin 5´-diphosphate and RMP). In a recombinant human UGT1A1 assay, the assay buffer components uridine and its phosphorylated derivatives are isobaric with RBV and its phosphorylated metabolites, leading to significant interference when analyzed by LC-MS with the nominal mass resolution mode.

RESULTS

Presented here is a LC-MS method employing LC coupled with full-scan high-resolution accurate MS analysis for the simultaneous quantitative determination of RBV, RMP, ribavirin 5´-diphosphate and RTP by differentiating RBV and its phosphorylated metabolites from uridine and its phosphorylated derivatives by accurate mass, thus avoiding interference.

CONCLUSION

The developed LC-high-resolution accurate MS method allows for quantitation of RBV and its phosphorylated metabolites, eliminating the interferences from uridine and its phosphorylated derivatives in recombinant human UGT1A1 assays.

Anemia and thrombocytosis induced by ribavirin monotherapy in patients with chronic hepatitis C

BACKGROUND

An inosine triphosphatase (ITPA) single-nucleotide polymorphism (SNP) is associated with anemia induced by pegylated interferon and ribavirin (RBV) combination therapy in patients with chronic hepatitis C (CHC). However, there are very few reports on the hematological effects of RBV monotherapy. Here, hematological changes were monitored in patients with CHC who received RBV monotherapy, and the mechanism of these changes was investigated.

METHODS

Patients with CHC (n = 30) received RBV monotherapy for 4 weeks. The RBV dose was determined on the basis of body weight. Complete blood count, and serum erythropoietin (EPO) and thrombopoietin (TPO) levels were assessed. The associations between these parameters and the ITPA SNP (rs1127354) were analyzed.

RESULTS

Over the 4 weeks, the median hemoglobin level of all patients decreased significantly, from 13.6 (10.5-16.6) to 11.7 (9.4-14.9) g/dl (P < 0.001), and the platelet counts increased, from 14.0 × 10(4) (8.9-37.4 × 10(4)) to 15.8 × 10(4) (10.2-40.6 × 10(4)) /mm(3) (P = 0.003). At week 4, hemoglobin levels differed between patients with the ITPA CC genotype and those with the AA or AC genotypes [11.1 (9.4-13.5) vs. 12.9 (12.5-14.9) g/dl, P = 0.001]. The platelet change ratio (i.e., platelet count at week 4/platelet count at baseline) in the patients with developing anemia was correlated with the increase in the serum EPO level over 4 weeks (r = 0.88, P = 0.002), but not with the increase in the serum TPO level over 4 weeks.

CONCLUSIONS

RBV monotherapy induced anemia and affected thrombocytosis in patients with CHC. Elevated endogenous EPO may stimulate platelet production.

Development and validation of a useful HPLC-UV method for quantification of total and phosphorylated-ribavirin in blood and erythrocytes of HCV+ patients

Ribavirin-induced hemolytic anemia is the main cause of discontinuation of the combination therapy with alpha-interferon-2b and ribavirin for the treatment of hepatitis C virus (HCV) infection. The determination of intracellular ribavirin levels in blood, including the levels of its phosphorylated metabolites, might be useful for predicting ribavirin-induced anemia, which could be caused by the accumulation of these molecules within the erythrocytes. In this work, we simplified and validated a previously developed assay method, to make it suitable for routine monitoring of cellular ribavirin. Whole blood diluted with a five-fold volume of ice-cold distilled underwent a process of acid phosphatase digestion to convert phosphorylated ribavirin metabolites to free ribavirin. The resulting mixture, spiked with an internal standard, was treated with a protein precipitation protocol in acetonitrile, followed by reverse-phase high-performance liquid chromatography analysis. The calibration curve for ribavirin levels in whole blood was linear at concentrations from 625 to 320,000 ng/mL (r(2)=0.998). Accuracy, intra-day and inter-day precision for ribavirin and phosphorylated-ribavirin quality controls were all below 9.0%. We tested this method by monitoring blood ribavirin concentrations in 13 HCV+ patients, receiving alpha interferon-plus ribavirin combination therapy.

Erythrocyte and plasma ribavirin concentrations in the assessment of early and sustained virological responses to pegylated interferon-alpha 2a and ribavirin in patients coinfected with hepatitis C virus and HIV

OBJECTIVES

To determine the relationship between erythrocyte and plasma ribavirin concentrations in hepatitis C virus (HCV)/HIV-coinfected patients, and to correlate ribavirin exposure with early and sustained virological response (EVR and SVR) and haemoglobin level reductions.

METHODS

Clinical and biological data from 68 HCV/HIV-coinfected patients were recorded at baseline, week 4 (W4), week 12 and at 24 weeks after completion of treatment. Plasma and erythrocyte ribavirin concentrations were determined 12 h after the final ribavirin dose (C(min)).

RESULTS

Erythrocyte ribavirin concentrations were 100-fold higher than plasma concentrations, with a significant relationship between them (P < 0.05). In patients with HCV genotype 1 or 4, a plasma ribavirin C(min) threshold of 1.95 mg/L at W4 tended to predict EVR [sensitivity 44%; specificity 87%; AUC 0.67 (95% CI 0.50-0.84)] and was predictive of SVR [sensitivity 58%; specificity 84%; AUC 0.71 (95% CI 0.51-0.90)]. Among patients with these HCV genotypes, an erythrocyte ribavirin C(min) threshold of 146 mg/L at W4 was found to be the best value for discriminating between responders and non-responders for both EVR [sensitivity 67%; specificity 75%; AUC 0.58 (95% CI 0.24-0.93)] and SVR [sensitivity 50%; specificity 80%; AUC 0.70 (95% CI 0.39-1.01)]. We also demonstrated a significant relationship between reduced haemoglobin levels and plasma ribavirin C(min) at W4 (P = 0.05).

CONCLUSIONS

Therapeutic drug monitoring may be useful for the management of anti-HCV treatment in HCV/HIV-coinfected patients.

Optimal erythrocyte ribavirin level to reduce the risk of anemia and obtain an early virological response in patients with chronic hepatitis C caused by genotype 1b infection

Aims. To determine whether the erythrocyte phosphorylated ribavirin (RBV) level might be a useful index of EVR and risk of anemia and to determine the optimal dose of RBV in 24 patients with hepatitis C with pegylated interferon and RBV. Methodology. The RBV level was measured by a high-performance liquid chromatography. Results and Conclusion. In patients aged 50 years or over, a negative correlation (r = -0.548, P < .05) was observed between the RBV level at week 2 and rate of Hb reduction (ΔHb) at week 4. The ΔHb at week 4 was significantly greater in patients with RBV levels of ≥800 μM (-25.5 ± 10.1%) than in patients with RBV levels <800 μM (-15.6 ± 7.7%). None of the patients with RBV levels <600 μM at week 2 achieved EVR and SVR. Thus the optimal levels of erythrocyte phosphorylated RBV at week 2 of therapy in order to achieve EVR without anemia seemed to be 600-800 μM.

Plasma/erythrocyte ribavirin x100 ratio as an indicator of sustained virological response in HCV genotype 1 patients with early virological response

BACKGROUND

On-treatment predictors during antiviral therapy of HCV are useful because they allow discontinuation of an unnecessary treatment in non-responders. Our aim was to evaluate the usefulness of plasma and erythrocyte ribavirin levels in predicting sustained virological response (SVR) in HCV genotype 1 patients undergoing antiviral treatment.

METHODS

A total of 40 HCV genotype 1 patients treated with pegylated interferon-alpha2a 180 microg weekly plus ribavirin 1,000 or 1,200 mg daily (according to body weight) were included in the study. Plasma and erythrocyte ribavirin levels were evaluated in all patients at week 12 by HPLC. At week 24, ribavirin levels were reassessed in those achieving early virological response (EVR).

RESULTS

A total of 27 patients achieved EVR, whereas 17 achieved SVR. There was no difference among EVR and non-EVR patients in terms of plasma and erythrocyte ribavirin concentrations at week 12. At week 24, EVR patients obtaining SVR exhibited higher mean +/-sd levels of ribavirin in plasma and lower levels in erythrocytes compared with non-SVR patients (in plasma 12.8 +/-10 versus 5.8 +/-4 microM [P<0.02] and in erythrocytes 1,053 +/-504 versus 1,613 +/-589 microM [P<0.03]). When the plasma ribavirin/erythrocyte ribavirin x100 ratio was compared, the difference was enhanced (1.5 +/-1.3 versus 0.4 +/-0.3 microM; P<0.01). Receiver operating characteristic curve analysis identified a cutoff for plasma ribavirin/erythrocyte ribavirin x100 ratio in predicting SVR of 0.71 with a negative predictive value of 0.8 and a positive predictive value of 0.9, whereas those related to EVR were 1 and 0.6, respectively.

CONCLUSIONS

Plasma ribavirin/erythrocyte ribavirin x100 ratio at week 24 seems to be a good indicator of SVR in HCV genotype 1 patients achieving EVR.

The utility of therapeutic drug monitoring for ribavirin in patients with chronic hepatitis C--a critical review

OBJECTIVE

To evaluate the utility of therapeutic drug monitoring (TDM) for ribavirin in chronic hepatitis C.

DATA SOURCES

Literature searches were conducted through PubMed (1949-June 2009), EMBASE (1980-June 2009), BIOSIS Previews (1969-June 2009), International Pharmaceutical Abstracts (1970-June 2009), Google, and www.clinicaltrials.gov using the terms ribavirin, therapeutic monitoring, hepatitis C, and drug levels. In addition, pertinent reference citations from identified publications were reviewed. Studies were limited to English language, adult age, and human subjects.

STUDY SELECTION AND DATA EXTRACTION

All articles identified from the data sources were evaluated. Studies that measured ribavirin concentrations or dose and treatment response were included in the review.

DATA SYNTHESIS

While monitoring of ribavirin plasma concentrations to improve treatment response in patients with chronic hepatitis C has been described in the literature, the utility of TDM for ribavirin in this group of patients has not been systematically studied. Thus, a previously published 9-step decision-making algorithm was employed to help determine whether TDM is warranted, based on currently available evidence. Thirty articles involving patients with chronic hepatitis C mono-infection, 12 for hepatitis C-HIV coinfection, 5 for renal dysfunction, and 5 for post-liver transplant patients were reviewed. In all subpopulations, studies exist that either support or refute the usefulness of ribavirin TDM. Additionally, the majority of the included studies had methodologic limitations, such as small sample size, retrospective analyses, and lack of p value adjustment for multiple analyses. Large randomized controlled trials would help to definitively answer this question.

CONCLUSIONS

There is conflicting evidence about the existence of a correlation between ribavirin concentrations and virologic response or development of toxicity. This inconsistent evidence, coupled with the currently employed effective strategies that maximize sustained virologic response and minimize development of anemia, precludes the utility of TDM for ribavirin.

HPLC-MS/MS method for the intracellular determination of ribavirin monophosphate and ribavirin triphosphate in CEM ss cells

A sensitive and specific method using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) for the determination of ribavirin monophosphate (RBV-MP) and ribavirin triphosphate (RBV-TP) in cells has been developed and validated. In this method, ribavirin phosphorylated metabolites were extracted and separated by anion exchange solid phase extraction (SPE). The RBV-MP and RBV-TP fractions were dephosphorylated using acid phosphatase and further purified by phenyl boronate SPE prior to HPLC-MS/MS analysis. (13)C(5)-uridine was added as internal standard to obtain better accuracy and precision of the analysis. The MS/MS detector was optimized at multiple reaction monitoring (MRM) using positive electrospray ionization to detect 245-->113 and 250-->133 transitions for ribavirin and internal standard, respectively. The calibration curve was linear over a concentration range of 0.01-10 microg/mL with a limit of quantitation of 0.01 microg/mL. Mean inter-assay accuracy and precision for RBV-MP and RBV-TP quality control samples at 0.03, 0.3 and 8 microg/mL were 5% and 10%, respectively. This method was successfully used for the in vitro determination of RBV-MP and RBV-TP in CEM(ss) cells cultured with RBV.

Prediction of Sustained Virological Response by Ribavirin Plasma Concentration at Week 4 of Therapy in Hepatitis C virus Genotype 1 Patients

Background

Pegylated interferon/ribavirin combination is currently the standard treatment for chronic hepatitis C virus (HCV) infection. Body weight adjustment of ribavirin is crucial for response. However, previous studies found no relation between ingested dose and plasma concentration. The aim of this study was to define the ribavirin trough plasma concentration at week 4 (W4) associated with sustained virological response (SVR).

Methods

Thirty-one HCV genotype 1 patients (8 naive and 23 non-responders to a previous pegylated interferon/ribavirin therapy) were treated with pegylated interferon/ribavirin and assessed by HPLC for ribavirin plasma concentration at W4.

Results

Eleven patients (35%) achieved SVR, whereas 20 (65%) were non-responders. The median ribavirin plasma concentration at W4 (1.90 mg/l) varied from 1.62 mg/l in patients with subsequent non-response to 2.28 mg/l in sustained responders ( P=0.007). Receiver operating characteristic curve analysis indicated that the 2.01 mg/l threshold gave the best sensitivity and specificity (73% and 80%, respectively, area under the curve=0.80; P=0.007). Sixty-seven percent of patients with median ribavirin plasma concentration >2 mg/l achieved SVR versus only 16% below this level ( P=0.007). Multivariate regression analysis indicated that a ribavirin plasma concentration >2 mg/l at W4 was associated with SVR independent of gender, age, weight, baseline viral load and response to previous therapy.

Conclusion

These results, which remain to be confirmed in large clinical trials, highlight the potential relevance of ribavirin plasma level monitoring at an early stage of treatment. This monitoring could be of help in guiding antiviral therapy by offering dose adjustment in patients with ribavirin plasma level below the 2 mg/l threshold.

Blood ribavirin concentration in high-dose ribavirin for adenovirus-induced haemorrhagic cystitis - a case report

Blood ribavirin concentration was monitored after the administration of high-dose oral ribavirin in a case of adenovirus-induced haemorrhagic cystitis post-stem-cell transplantation. Combination use of intravenous gamma immunoglobulin (15 g/3 days) and high-dose ribavirin (RBV; 9000 mg/4 days) provided plasma ribavirin concentration of 24.3 microM and achieved virus eradication. High level of erythrocyte ribavirin (1085 microM; mostly as phosphorylated metabolites) with long half-life (15 days) caused severe anaemia, which required several blood transfusions for 2 weeks after the cessation of the ribavirin treatment. It was suggested that blood transfusion and intensive haemoglobin level monitoring is necessary for at least 4 weeks after the RBV, because of the high accumulation of phosphorylated ribavirin in erythrocytes even after stopping ribavirin administration.

Human uridine-cytidine kinase phosphorylation of ribavirin: a convenient method for activation of ribavirin for conjugation to proteins

Ribavirin is a synthetic nucleoside analog that is used for the treatment of hepatitis C virus (HCV) infection. Its primary toxicity is hemolytic anemia, which sometimes necessitates dose reduction or discontinuation of therapy. Selective delivery of ribavirin into liver cells would be desirable to enhance its antiviral activity and avoid systemic side effects. One approach to liver-specific targeting is conjugation of the ribavirin with asialoglycoprotein that is taken up specifically by liver cells. Human uridine-cytidine kinase-1 (UCK-1) was used for ribavirin phosphorylation to its monophosphate form. 1-Ethyl-3-diisopropylaminocarbodiimide (EDC) was used as a coupling agent. The best results were obtained using direct conjugation protocol with a molar ratio of 6.5 ribavirin monophosphate (RMP) molecules per one asialoorosomucoid (AsOR) molecule. Our findings show that ribavirin is a potential substrate of UCK-1, and RMP formed could be chemically coupled to AsOR to form a conjugate for liver specific targeting.

Ribavirin: Analytical determinations since the origin until today

Ribavirin (RV) (1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamide), is a synthetic purine nucleoside analog with a broad spectrum of antiviral activity. To better understand the mechanism of action of RV, as well as its pharmacokinetic characteristics, an assay that can allow specific, sensitive, and accurate measurement of RV in biologic samples is critical. In this way, diverse analytical methods have been established. In this work, we have recompiled these methods with the aim to present the different options for the RV determination.

Early ribavirin pharmacokinetics, HCV RNA and alanine aminotransferase kinetics in HIV/HCV co-infected patients during treatment with pegylated interferon and ribavirin

BACKGROUND/AIMS

We evaluated whether early ribavirin pharmacokinetics differ comparing hepatitis C/human immunodeficiency virus coinfected sustained virological responders and nonresponders.

METHODS

Twenty-four treatment-naive coinfected patients received pegylated-interferon alfa-2b (12 kDa) (1.5 microg/kg) once weekly plus daily ribavirin (13.6 mg/kg/d) for up to 48 weeks. Serum HCV RNA, serum alanine aminotransferase, and plasma ribavirin levels were measured frequently during the first 16 days of therapy and monthly thereafter.

RESULTS

Six patients were sustained responders. During the first 4 weeks of treatment, median plasma ribavirin levels and area under the ribavirin curve were significantly lower (p<0.0001 and p<0.01, respectively) in sustained responders compared with nonresponders. Compared to ribavirin levels at weeks 2 and 4, ribavirin levels in sustained responders continued to increase significantly until week 8 (p<0.02). At week 4, hemoglobin declines were significantly (p=0.002) greater in sustained responders than nonresponders. At week 1, serum HCV RNA levels and changes in alanine aminotransferase levels relative to baseline could identify likely responders better than plasma ribavirin levels.

CONCLUSIONS

We conjecture that intracellular ribavirin accumulation may be enhanced early in treatment in coinfected sustained responders, although this hypothesis should be investigated further. At week 1, serum HCV RNA and changes in alanine aminotransferase levels relative to baseline might identify likely responders.

Simultaneous determination of ribavirin and ribavirin base in monkey plasma by high performance liquid chromatography with tandem mass spectrometry

For the first time, a liquid chromatographic method with tandem mass spectrometric detection (LC-MS/MS) for the simultaneous determination of ribavirin and rabavirin base was developed and validated over the concentration range of 10-5,000 ng/ml, respectively, using a 0.025 ml monkey plasma sample. Ribavirin, ribavirin base, and the internal standards were extracted from monkey plasma via protein precipitation. After evaporation of the supernatant, the extract was reconstituted with 5% methanol (containing 0.1% formic acid) and injected onto the LC-MS/MS system. Optimum chromatographic separation was achieved on a Waters Atlantis dc18 (150 mm x 2.1mm, 5 microm) column with mobile phase run in gradient with 100% water containing 0.5% formic acid (A) and 90% acetonitrile (containing 0.5% formic acid (B). The flow rate was 0.4-0.6 ml/min with total cycle time of approximately 7.0 min. Post-column addition of acetonitrile (containing 0.1% formic acid) at 0.3 ml/min was used to increase the ionization efficiency in the MS source. The method was validated for sensitivity, linearity, reproducibility, stability and recovery. Lack of adverse matrix effect and carry-over was also demonstrated. The intra-day and inter-day precision and accuracy of the quality control (QC) samples were <9.0% relative standard deviation (R.S.D.) and 10.8% bias for ribavirin, and 10.3% R.S.D. and 11.3% bias for ribavirin base. The current specific, accurate and precise assay is useful in support of the toxicokinetic and pharmacokinetic studies of these compounds.

Ribavirin and mycophenolic acid markedly potentiate the anti-hepatitis B virus activity of entecavir

MPA [the active metabolite of the immuno-suppressive agent CellCept] and ribavirin markedly potentiate the anti-HBV activity of the guanine-based nucleoside analogue entecavir (ETV) against both wild-type HBV and a lamivudine-resistant variant. Ribavirin (in its 5'-monophosphate form) and MPA are inhibitors of IMP-dehydrogenase and cause depletion of intracellular dGTP pools. The active triphosphorylated form of ETV may inhibit more efficiently the priming reaction, reverse transcription and DNA-dependent DNA polymerase activity of the HBV polymerase in the presence of reduced levels of dGTP. The potential for enhanced ETV activity is supported by the observation that exogenously added deoxyguanosine reversed the potentiating effect of ribavirin and MPA. Our observations may have important implications for those (liver) transplant recipients that receive MMF as part of their immunosuppressive regimen and who, because of a de novo or a persistent infection with HBV need antiviral therapy such as ETV. Further studies will need to be conducted to determine if combining ribavirin (a compound used for the treatment of HCV infections) with ETV could have an advantage for the treatment of HBV infections, in particular in patients co-infected with HCV.

LC-MS/MS method for simultaneous determination of viramidine and ribavirin levels in monkey red blood cells

A high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed for the simultaneous determinations of total viramidine (viramidine, viramidine monophosphate, viramidine diphosphate, and viramidine triphosphate) and total ribavirin (ribavirin, ribavirin monophosphate, ribavirin diphosphate, and ribavirin triphosphate) in monkey red blood cells (RBC). The method involves the addition of internal standards and perchloric acid, conversion of viramidine or ribavirin phosphorylated metabolites to viramidine or ribavirin, purification with an aminopropyl (NH(2)) solid phase extraction (SPE) cartridge, and LC-MS/MS analysis. The MS/MS is selected to monitor m/z 245-->113, 250-->113, 244-->112, and 249-->112 for ribavirin, [(13)C]ribavirin, viramidine, and [(13)C]viramidine, respectively, using positive electrospray ionization. The calibration curves are linear over a concentration range of 100-10,000 ng/mL (0.412-41.2 microM) with a lower limit of quantification (LLOQ) of 100 ng/mL for both compounds. Mean inter-assay recoveries for ribavirin are 101%, 98.9%, and 96.0%, with coefficient of variance (%CV) values between 1.95 and 4.50% for 100, 1000, and 10,000 ng/mL quality control (QC) samples, respectively. Mean inter-assay recoveries for viramidine are 96.3%, 101%, and 102%, with coefficient of variation (%CV) values between 3.61 and 7.22%, for 100, 1000, and 10,000 ng/mL QC samples, respectively. Over-curve dilution QC at 400 microg/mL (1639 microM) for both viramidine and ribavirin are used to ensure the dilution accuracy (25 X dilutions) for monkey samples. The method has been used to simultaneously determine the total concentrations of ribavirin and viramidine in monkey RBC following 5, 15, and 36 weeks dosing of viramidine or ribavirin (60 mg/kg). The concentrations of total ribavirin following ribavirin dosing are 1242 microM at week 5, 1257 microM at week 15, and 1146 microM at week 36. The concentrations of total ribavirin following viramidine dosing are 634 microM at week 5, 716 microM at week 15, and 683 microM at week 36. Only small amounts of viramidine are detected in RBC following viramidine dosing, 7.80 microM at week 5, 6.63 microM at week 15, and 10.4 microM at week 36. The results suggest that ribavirin levels in RBC were at steady state at week 5 of ribavirin or viramidine dosing. At steady state, ribavirin levels in RBC are approximately 2x after ribavirin dosing than viramidine dosing. The relatively small percentage of viramidine in RBC suggests that viramidine either poorly penetrated into RBC or was extensively converted to ribavirin following entry into RBC.

Plasma ribavirin concentrations during treatment of recurrent hepatitis C with peginterferon alpha-2b and ribavirin combination after liver transplantation

After liver transplantation (LT) for hepatitis C virus (HCV)-related cirrhosis, recurrence of HCV infection is universal. The efficacy of antiviral therapy in this indication is usually reduced because of its poor tolerability. We present herein the results of plasma measurement of ribavirin levels in transplanted patients when using increasing dosage of ribavirin, in comparison with a control cohort of nontransplanted patients. Seventeen control patients (nine women and eight men, median age 51.5 years) were compared with 12 liver transplant patients (2 women and 10 men, median age 55 years). In 76% of patients, HCV infection was genotype 1. All patients were treated by a combination of ribavirin and pegylated-interferon alpha-2b. A total of 54 blood samples were taken (1.8 per patient) for ribavirin level measurement. A virological response was obtained in 8/17 patients in the control group and in 6/12 LT patients. Ribavirin dose was lower in the LT group (8.79 vs 12.98 mg/kg/day), but plasma levels were the same in both groups (2.23 vs 2.43 mg/L for LT and non-LT groups, respectively). This was probably related to impaired renal function in the LT group (serum creatinine: 112.6 vs 73.6 micromol/L). No discontinuation of ribavirin therapy was observed and haemoglobin level was the same in both groups (109.5 g/L in LT patients vs 119.5 g/L in the control group). These results strongly support the interest in plasma measurement of ribavirin concentration during antiviral therapy in LT patients. Ribavirin dosage might be adapted without compromising its efficacy.

Ribavirin Levels in Post Liver Transplant Patients Treated for Recurrent Hepatitis C Viral Infection

Hepatitis C virus (HCV) infection is the most common indication for liver transplantation (LTx) in the United States. Ribavirin with pegylated interferon is the only treatment option for HCV recurrence in post-LTx patients. In clinical practice, for more than 50% of patients, ribavirin dose needs to be modified.

AIM

The aim of this study was to examine the role of ribavirin level and its relevance in the management of post-LTx patients in terms of renal dysfunction, efficacy, toxicity, and potential drug interactions.

PATIENTS AND METHODS

Thirty-four blood samples were available from 22 post-LTx patients. Ribavirin concentrations in plasma (all samples) and whole blood concentrations (16 samples) were examined. The dose of ribavirin ranged from 400 mg/d to 1000 mg/d, but concentrations were normalized to 800 mg/d.

RESULTS

There was a wide variation in plasma concentration of ribavirin, ranging from 1.8 to 122.1 mg/mL. The concentrations were similar in whole blood and plasma. Dose-normalized concentration with creatinine clearance below 70 mL/min were significantly higher when compared with creatinine clearance above 70 mL/min (P = .015). Eleven patients required erythropoietin; their mean ribavirin dosage was higher but mean ribavirin concentration was lower compared to the 11 patients who did not require erythropoietin factor. There was no difference in mean ribavirin concentration in patients who cleared the virus (n = 7) compared and who did not clear the virus (n = 9). Three patients were on nucleoside reverse transcriptase inhibitors (NRTI) had significantly higher concentration (mean 87.1 microg/mL) compared to those who did not receive NRTI (mean 34.4 microg/mL, P = .00)

CONCLUSION

Ribavirin concentration in plasma and whole blood were similar, with a wide variation. Patients with impaired renal function and those who were on NRTI had significantly higher concentrations of ribavirin. The ribavirin concentrations did not predict either the clearance of HCV RNA or the need for erythropoitin factor.

Epoetin alfa for the treatment of combination therapy-induced hemolytic anemia in patients infected with hepatitis C virus

In the United States, about 2.7 million people are chronically infected with the hepatitis C virus, accounting for nearly 1.8% of the population. The current standard of therapy is a combination of pegylated interferon products and ribavirin. A common adverse effect associated with this therapy is anemia, which is frequently referred to as mixed anemia because of the synergistic contribution of the interferons and ribavirin. The effect of ribavirin on the development of anemia is considered greater than that of interferon. The current standard of practice for treating this adverse effect is reduction of the dosages of both drugs, at prespecified hemoglobin levels. However, recent findings underscore the importance of maintaining adequate dosages of interferon and ribavirin, which may be crucial in achieving an early virologic response and a sustained virologic response in treating patients with hepatitis C infection. Treatment with epoetin alfa for this mixed anemia significantly improved hemoglobin levels and quality of life, and enabled adequate dosages of ribavirin to be maintained. Future studies should address several issues: when to start epoetin alfa treatment, the duration of treatment, the drug's optimal dosage, its effects on end-of-treatment and sustained virologic response rates, and a cost analyses.

Simple fluorimetric method for determination of certain antiviral drugs via their oxidation with cerium (IV)

A simple and sensitive fluorimetric method for determination of antiviral drugs: ribavirin, acyclovir, and amantadine hydrochloride has been developed. The method was based on the oxidation of these drugs by cerium(IV) in presence of perchloric acid and subsequent monitoring the fluorescence of the induced cerium(III) at lambdaexcitation 255 and lambdaemission 355 nm. Different variables affecting the reaction conditions such as the concentrations of cerium(IV), type and concentration of acid medium, reaction time, temperature, and the diluting solvents were carefully studied and optimized. Under the optimum conditions, linear relationships with good correlation coefficients (0.9978-0.9996) were found between the relative fluorescence intensity and the concentrations of the investigated drugs in the range of 50-1400 ng ml-1. The assay limits of detection and quantitation were 20-49, and 62-160 ng ml-1, respectively. The precision of the method was satisfactory; the values of relative standard deviations did not exceed 1.58%. No interference could be observed from the excipients commonly present in dosage forms. The proposed method was successfully applied to the analysis of the investigated drugs in pure and pharmaceutical dosage forms with good accuracy and precision; the recovery percentages ranged from 99.2 to 101.2+/-0.48-1.30%. The results obtained by the proposed fluorimetric method were comparable with those obtained by the official method stated in the United States Pharmacopoeia.

Liquid chromatography assay for routine monitoring of cellular ribavirin levels in blood

Ribavirin-induced hemolytic anemia is one cause for cessation of combination therapy with alpha interferon 2b and ribavirin for hepatitis C infection. Determining cellular ribavirin levels in blood, including the levels of its phosphorylated metabolites, might be useful for predicting ribavirin-induced anemia, because the metabolites accumulate in erythrocytes. We simplified an assay method developed previously to make it suitable for routine monitoring of cellular ribavirin. Whole blood diluted with a sixfold volume of ice-cold distilled water was subjected to acid phosphatase digestion to convert phosphorylated ribavirin metabolites to free ribavirin. The resulting mixture, spiked with an internal standard, was treated by phenyl boronic acid column extraction, followed by reverse-phase high-performance liquid chromatography analysis. The calibration curve for ribavirin levels in whole blood was linear at concentrations of 5.3 to 1,024 microM (r(2) = 0.9999). Validation coefficients of variation for intra- and interday assays were 2.9 to 5.8% and 4.3 to 8.3%, respectively. We tested this method by monitoring blood ribavirin concentrations in two hepatitis C patients receiving alpha interferon 2b-plus-ribavirin combination therapy.

Effects of ribavirin on cytokine production of recall antigens and phytohemaglutinin-stimulated peripheral blood mononuclear cells. (Inhibitory effects of ribavirin on cytokine production)

AIM

To evaluate the effects of ribavirin on cytokine production of recall antigen and PHA-stimulated PBMC obtained from healthy individuals.

MATERIALS AND METHODS

PBMC were challenged with tetanus toxoid (5 microg/mL) and PHA (10 microg/mL) in absence or presence of ribavirin at different concentrations (1, 10 and 100 (microM). Parallel sets of wells containing PBMC exposed to medium alone were used as negative controls. On day 3 after initiation of the cultures, IL-2, IFN-gamma, IL-4, IL-10, TNF-alpha content were determined in supernatants of PBMC from the different individuals.

RESULTS

The effects of ribavirin on cytokine released by human PBMC in response to PHA and TT showed a great variation among individuals. No significant changes were observed between 1-10 microM concentrations in the production of TNF-alpha, IFN-gamma and IL-10 by both PHA and TT-stimulated PBMC. Ribavirin inhibited TNF-alpha, IFN-gamma, and IL-10 in both PHA and TT-stimulated PBMC at 100 microM (p <0.05). At this concentration, ribavirin induced an increase of 124% in the production of IL-2 by PHA-stimulated PBMC (p <0.05).

CONCLUSIONS

The present data suggest that ribavirin may cause diverse effects on immunoregulatory cytokine secretion with changes in the Th1/Th2 balance.

Low membrane protein sulfhydrils but not G6PD deficiency predict ribavirin-induced hemolysis in hepatitis C

Hemolysis is a frequent adverse effect of ribavirin (RBV). It has been suggested that oxidative stress plays a role, but mechanisms and predictive risk factors for severe forms remain unknown. Markers of redox status were determined in erythrocytes of 34 patients with hepatitis C-four of them with glucose-6-phosphate-dehydrogenase (G6PD) deficiency-before and during treatment with RBV and interferon (IFN) and were compared with 10 healthy control subjects. In addition, erythrocytes were incubated with RBV, and the effects of dipyridamole (DPD), diethylmaleate (DEM), and glutathione ester (GSHE) were studied in vitro. Of the 30 patients without G6PD deficiency who were treated with RBV and IFN-alpha, five developed major hemolysis (Delta hemoglobin > 6 g/dL) and 25 developed minor hemolysis (Delta hemoglobin < 2.5 g/dL). Patients with major hemolysis had lower median pretreatment values of membrane protein sulfhydrils than patients with minor hemolysis (28.4 vs. 36.7 nmol/mg, P <.001). Erythrocytes of G6PD-deficient patients were not more susceptible to RBV-induced hemolysis. In in vitro incubations of erythrocytes, DEM enhanced the RBV-induced decrease of glutathione, protein sulfhydrils, and osmotic resistance. Supplementation of GSHE and DPD prevented the RBV-induced decrease in osmotic resistance, adenosyl triphosphate (ATP), and 2,3-diphosphoglycerate (DPG), the loss of glutathione and protein sulfhydrils, and the formation of thiobarbituric acid reactive substances (TBARs). In conclusion, the data indicate that low membrane protein sulfhydrils prior to therapy but not G6PD deficiency are predictive of RBV-induced major hemolysis. In vitro, GSHE and DPD reduce the RBV-associated oxidative stress in erythrocytes and prevent the increase in osmotic fragility, suggesting that these compounds might decrease the risk of hemolysis in patients.

Marked elevation of erythrocyte ribavirin levels in interferon and ribavirin-induced anemia

BACKGROUND & AIMS

To elucidate the effects of blood ribavirin disposition on ribavirin-induced anemia, the relationship between erythrocyte ribavirin concentration and change in hematologic parameters was examined in interferon and ribavirin combination therapy for HCV eradication.

METHODS

Nine HCV RNA-positive patients were treated with combination therapy including 11.3 +/- 1.2 mg.kg(-1).day(-1) of ribavirin. Blood concentrations of ribavirin and its phosphorylated metabolites were measured in plasma as well as erythrocyte.

RESULTS

Blood ribavirin concentrations gradually increased to steady-state levels of 8.8 +/- 1.4 micromol/L and 1389 +/- 371 micromol/L in plasma and erythrocytes, respectively, within 3-4 weeks of initiating therapy. Erythrocyte phosphorylated metabolite levels (1215 +/- 302 micromol/L) were found to be exceedingly high, i.e., 87% of the measured erythrocyte ribavirin concentration. In contrast, plasma phosphorylated metabolite levels were undetectable. Positive correlation was found to exist between erythrocyte ribavirin concentrations and a decrease in hemoglobin (r = 0.620, P < 0.001).

CONCLUSIONS

We concluded that marked elevation of erythrocyte ribavirin including its phosphorylated metabolites was associated with hemoglobin reduction, leading to interferon and ribavirin-induced anemia.