Stability of ribavirin concentrations depending on the type of blood collection tube and preanalytical conditions

A descriptive systematic review of salivary therapeutic drug monitoring in neonates and infants

AIMS

Saliva, as a matrix, offers many benefits over blood in therapeutic drug monitoring (TDM), in particular for infantile TDM. However, the accuracy of salivary TDM in infants remains an area of debate. This review explored the accuracy, applicability and advantages of using saliva TDM in infants and neonates.

METHODS

Databases were searched up to and including September 2016. Studies were included based on PICO as follows: P: infants and neonates being treated with any medication, I: salivary TDM vs. C: traditional methods and O: accuracy, advantages/disadvantages and applicability to practice. Compounds were assessed by their physicochemical and pharmacokinetic properties, as well as published quantitative saliva monitoring data.

RESULTS

Twenty-four studies and their respective 13 compounds were investigated. Four neutral and two acidic compounds, oxcarbazepine, primidone, fluconazole, busulfan, theophylline and phenytoin displayed excellent/very good correlation between blood plasma and saliva. Lamotrigine was the only basic compound to show excellent correlation with morphine exhibiting no correlation between saliva and blood plasma. Any compound with an acid dissociation constant (pKa) within physiological range (pH 6-8) gave a more varied response.

CONCLUSION

There is significant potential for infantile saliva testing and in particular for neutral and weakly acidic compounds. Of the properties investigated, pKa was the most influential with both logP and protein binding having little effect on this correlation. To conclude, any compound with a pKa within physiological range (pH 6-8) should be considered with extra care, with the extraction and analysis method examined and optimized on a case-by-case basis.

Concentration Monitoring of Plasma Ribavirin: Validation of a Liquid Chromatography-Mass Spectrometric Method and Clinical Sample Collection

BACKGROUND

A liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was developed for routine measurement of ribavirin concentrations in EDTA-anticoagulated plasma.

METHODS

After protein precipitation, we used a bridged ethylene hybrid (hydrophilic interaction) chromatography column, 0.1 mmol/L ammonium formate pH 3.0, and a gradient of 85%-96% acetonitrile to achieve baseline separation of ribavirin from isobaric uridine. Quantitation was assured using both primary (m/z 245.3 > 113.0) and secondary transitions (m/z 245.3 > 96.0) of the protonated species. Chromatographic separation and column washing also negated interference from major phospholipid species.

RESULTS

There was a linear relationship between concentration and response to 10 mg/L, with a minimum detectable level and a minimum level of quantitation both of 0.1 mg/L. Imprecision within the assay was <10% at 0.1 mg/L and <6% between assays for concentrations >0.4 mg/L. Bias was <4%. In clinical samples (n = 12), there was no difference in ribavirin concentrations obtained by an established liquid chromatographic assay with ultraviolet detection. Ribavirin concentrations were stable in plasma stored at room temperature for 3 days but then decreased significantly on day 7. Plasma concentrations were stable for 15 weeks at -20 °C. Concentrations in plasma separated from whole blood at room temperature fell by a median of 19.4% at 4 hours and then rose substantially (median 251% by 3 days). Dose-normalized ribavirin concentrations reached a steady state after a mean of >6 weeks treatment in 76 patients with hepatitis C.

CONCLUSIONS

A hydrophilic interaction liquid chromatography-tandem mass spectrometric method to measure ribavirin in plasma was developed. Samples for ribavirin estimation should be kept at 4 °C, separated within 2 hours of collection and stored at 4 °C before analysis, with long-term storage at -20 °C. This method was applied to a study of the ribavirin therapeutic monitoring in patients with hepatitis C.

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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.

Measuring ribavirin concentrations during the earliest stages of antiviral therapy for hepatitis C: potential relevance for treatment outcome

BACKGROUND

Correlations between ribavirin (RBV) concentrations and sustained virological response (SVR) to hepatitis C virus treatment have been demonstrated previously. As steady state is reached after several weeks of RBV treatment, dose modifications based on steady-state levels can only be applied relatively late in treatment, possibly too late to influence SVR rates. The authors aimed to determine whether measurement of early concentrations is useful to predict optimal steady-state RBV concentrations.

METHODS

In 61 treatment-naive genotype 1/4 patients RBV concentrations were determined in samples collected after 1, 2, 4, 8, 12, and 24 weeks of therapy. RBV concentrations were compared between responders and nonresponders; Receiver Operating Characteristic analyses were conducted to find optimal cut-off values to predict week 8 concentrations from earlier measurements.

RESULTS

Median week 8 RBV concentrations were significantly higher in patients with SVR compared with those without: 3.4 (interquartile range 2.4-3.9) versus 2.6 (interquartile range 2.0-3.5) mg/L (P < 0.05). RBV concentration at week 8 was an independent predictor of SVR [adjusted odds ratio 2.3 (95% confidence interval: 1.1-4.9; P = 0.03)]. The optimal cut-off value of week 8 RBV concentration to predict SVR was 2.20 mg/L [sensitivity 87%, specificity 40%, positive predictive value 64%, negative predictive value 71%]. Optimal cut-off values at weeks 1, 2, or 4 to predict an RBV concentration ≥2.20 mg/L at week 8 were 0.92, 1.29, and 1.67 mg/L, respectively, with positive predictive values and negative predictive values ranging from 88% to 91% and 71% to 86%, respectively.

CONCLUSIONS

RBV concentrations in the earliest stages of antiviral therapy predict therapeutic steady-state concentrations, allowing timely dose adjustments with potential implications for treatment outcome.

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.

A pharmacological profile of ribavirin and monitoring of its plasma concentration in chronic hepatitis C infection

Chronic hepatitis C (CHC) infection, usually an asymptomatic infection, has long-term serious complications such as cirrhosis, hepatocellular carcinoma, and end-stage liver disease requiring liver transplantation (LT). Several novel drugs against hepatitis C which form part of 'specifically targeted antiviral therapy for hepatitis C' (STAT-C) have been developed. These include NS3/4A protease inhibitors telaprevir, boceprevir, and nucleoside/non-nucleoside polymerase inhibitors (NS5A) which hold promise for future therapy. Despite the development of new anti-hepatitis C virus (HCV) drugs, ribavirin (RBV) remains the single most important drug to prevent relapse and is frequently included among newer regimens being developed with novel small molecule anti-HCV drugs. The current approved treatment is a combination therapy of once weekly subcutaneous pegylated-interferon (PEG-IFN)-α plus body-weight-based oral RBV regimen. The most significant dose-dependent side effect of RBV is hemolytic anemia warranting dose reduction or discontinuation in severe cases compromising sustained virological response (SVR). Monitoring RBV plasma concentration has been challenging due to its peculiar pharmacokinetics and has been done to predict both efficacy and toxicity. Herein, we review the pharmacological profile of RBV and the monitoring of its plasma concentration, monitoring in renal impairment, post-LT, and human immunodeficiency virus (HIV)-HCV co-infection in patients being treated with combination therapy of PEG-IFN-α and RBV.

Effect of an induction period of pegylated interferon-α2a and ribavirin on early virological response in HIV-HCV-coinfected patients: results from the CORAL-2 study

BACKGROUND

It is uncertain whether a 4-week induction period of pegylated interferon and ribavirin increases early virological response (EVR) in HIV-HCV-coinfected patients.

METHODS

HIV and HCV genotype 1- and 4-coinfected subjects were randomized to receive pegylated interferon-α2a 270 μg/week plus ribavirin 1,600 mg daily and epoetin-β for 4 weeks, followed by pegylated interferon-α2a at standard dosages plus weight-based ribavirin (WBR) dosage for 8 weeks (induction arm [IA]), or pegylated interferon-α2a plus WBR for 12 weeks (standard therapy arm [SA]). HCV RNA was determined at weeks 0, 1, 2, 3, 4, 8 and 12. Ribavirin plasma trough concentrations were determined at weeks 4 (RBV-C(4)) and 12 (RBV-C(12)).

RESULTS

A total of 67 patients were included; 33 in the SA and 34 in the IA. Overall, 25% received nucleoside reverse transcriptase inhibitor (NRTI)-sparing regimens. More patients achieved an HCV RNA decrease ≥1 log(10) at week 4 in the IA than in the SA (62% versus 38%; P=0.017), but EVR rates were similar in the two groups (74% versus 59% in the IA and SA, respectively; P=0.15). Independent predictors of faster HCV RNA decrease at 12 weeks were higher RBV-C(4) and younger age. RBV-C(4) were higher in patients allocated in the IA and in those receiving NRTIs (P=0.039).

CONCLUSIONS

A 4-week induction with pegylated interferon-α2a plus ribavirin was associated with a greater decrease in HCV RNA at week 4; however, this did not translate into higher EVR rates. Higher RBV doses and avoidance of NRTI-sparing antiretroviral regimens might improve HCV treatment efficacy.

Principles of therapeutic drug monitoring

Therapeutic drug monitoring (TDM) is central to optimize drug efficacy in children, because the pharmacokinetics and pharmacodynamics of most drugs differ greatly between children and adults. Many factors should be analyzed to implement TDM in the pediatric population, including a validated pharmacological parameter and an analytical method adapted to children as limited sampling volumes and high sensitivity are required. The use of population approaches, new analytical methods such as saliva and dried blood spots, and pharmacodynamic monitoring give attractive options to improve TDM, individualize therapy in order to optimize efficacy and reduce adverse drug reactions.

Collection of biological samples in forensic toxicology

Forensic toxicology is the study and practice of the application of toxicology to the purposes of the law. The relevance of any finding is determined, in the first instance, by the nature and integrity of the specimen(s) submitted for analysis. This means that there are several specific challenges to select and collect specimens for ante-mortem and post-mortem toxicology investigation. Post-mortem specimens may be numerous and can endow some special difficulties compared to clinical specimens, namely those resulting from autolytic and putrefactive changes. Storage stability is also an important issue to be considered during the pre-analytic phase, since its consideration should facilitate the assessment of sample quality and the analytical result obtained from that sample. The knowledge on degradation mechanisms and methods to increase storage stability may enable the forensic toxicologist to circumvent possible difficulties. Therefore, advantages and limitations of specimen preservation procedures are thoroughfully discussed in this review. Presently, harmonized protocols for sampling in suspected intoxications would have obvious utility. In the present article an overview is given on sampling procedures for routinely collected specimens as well as on alternative specimens that may provide additional information on the route and timing of exposure to a specific xenobiotic. Last, but not least, a discussion on possible bias that can influence the interpretation of toxicological results is provided. This comprehensive review article is intented as a significant help for forensic toxicologists to accomplish their frequently overwhelming mission.