Ribavirin therapeutic drug monitoring: why, when and how?

Population pharmacokinetics of ribavirin in lung transplant recipients and examination of current and alternative dosing regimens

BACKGROUND

Ribavirin is used in the treatment of respiratory paramyxovirus infection in lung transplant recipients; however, its pharmacokinetic profile in the transplant population is unknown despite the potential for alterations due to underlying pathology. Furthermore, the ability of current regimens to meet exposure targets has not been established.

OBJECTIVES

This study examined the pharmacokinetics of ribavirin in a lung transplant population for which current and alternative dosing regimens were assessed.

METHODS

Population pharmacokinetic modelling was conducted in NONMEM using concentration-time data from 24 lung transplant recipients and 6 healthy volunteers. Monte Carlo simulation was used to assess the ability of dosing regimens to achieve pre-specified target concentrations.

RESULTS AND CONCLUSIONS

A three-compartment model with first-order elimination most adequately described ribavirin concentration-time data, with CLCR and patient type (i.e. lung transplant) identified as significant covariates in the model. Simulations indicate that current regimens achieve efficacious concentrations within 24 h of treatment initiation that increase to supra-therapeutic levels over the treatment period. A regimen of 8 mg/kg q6h orally for 48 h followed by 8 mg/kg q24h orally for the remainder of the treatment period was predicted to result in >90% of patients exhibiting concentrations within the defined target range throughout the entire treatment course. Additional work to formally establish target therapeutic concentrations is required; however, this study provides a valuable first step in determining optimal ribavirin treatment regimens for paramyxovirus infections in the lung transplant population.

ITPA deficiency and ribavirin level are still predictive of anaemia in HCV-HIV-coinfected patients receiving ribavirin combined with a first-generation DAA (ANRS HC27 study)

BACKGROUND

We aimed to determine the impact of inosine triphosphatase (ITPA) deficiency on ribavirin (RBV)-induced anaemia in HIV-HCV-coinfected patients receiving a triple therapy including the haematotoxic direct-acting antiviral agent boceprevir (BOC).

METHODS

Patients of the ANRS HC27 BocepreVIH study were genotyped for two ITPA single nucleotide polymorphisms involved in ITPA deficiency. RBV trough concentration (Ctrough) was determined at week (W)4 and W8. Impact of ITPA deficiency on anaemia, RBV Ctrough, response and haematotoxicity (grade 3/4 anaemia, erythropoietin [EPO] use, RBV dose reduction or transfusion between day [D]0 and W8) was evaluated. Impact of RBV Ctrough on anaemia was also studied.

RESULTS

Among the 63 genotyped patients, 33% had a predicted ITPA deficiency. ITPA deficiency was associated with a lower haemoglobin (Hb) decline both at W4 (-1.0 g/dl versus -2.1 g/dl; P=0.02) and W8 (-2.7 g/dl versus -4.1 g/dl; P=0.05). None of the patients with ITPA deficiency received EPO between D0-W8 versus 26% of patients without ITPA deficiency (P=0.01). RBV Ctrough was associated with Hb decrease both at W4 and W8 and an RBV Ctrough cutoff value of 2 µg/ml was significantly associated with a W4 Hb decline >2 g/dl. Haematotoxicity was significantly associated with a lower W4 Hb level (P=0.017), absence of ITPA deficiency (P=0.018) and higher RBV Ctrough (P=0.012). ITPA deficiency, W4 RBV Ctrough and gender were independent predictors of anaemia at W4. ITPA deficiency was not associated with virological response.

CONCLUSIONS

ITPA deficiency and RBV Ctrough are still predictive of RBV-induced anaemia in HIV-HCV-coinfected patients treated with RBV combined with a first-generation direct antiviral agent.

Addition of boceprevir to PEG-interferon/ribavirin in HIV-HCV-Genotype-1-coinfected, treatment-experienced patients: efficacy, safety, and pharmacokinetics data from the ANRS HC27 study

BACKGROUND

Scarce data exist on the efficacy and safety of the PEGylated-interferon/ribavirin/boceprevir regimen in HIV/HCV-coinfected patients who failed to respond to PEGylated-interferon/ribavirin treatment.

OBJECTIVES

To evaluate the efficacy and safety of this drug regimen and the impact of the addition of boceprevir(BOC) on atazanavir (ATV) or raltegravir (RAL) pharmacokinetic parameters in a subgroup of patients.

METHODS

In this single-arm phase 2 trial, HIV-1/HCV-genotype-1-coinfected patients received PEGylated-interferonα2b (1.5 μg/kg/week)+ ribavirin (800-1400 mg/day) alone until W4 and with BOC(800 mgTID) until W48. Based on virologic response at W8, the three drugs were stopped or PEGylated-interferon/ribavirin was continued alone until W72. The primary endpoint was SVR at W24 off-therapy (SVR24).

RESULTS

64 patients were included. SVR24 was achieved in 53% of patients (CI90%: 43-63%) and in 90% of previous relapsers. In univariate analysis, SVR24 was associated with response to previous HCV treatment, HCV-1b subtype, HCV-RNA decline, ribavirin-Ctrough at W4, and HCV-RNA at W8 but not to fibrosis score, IL28B genotype, or boceprevir-Ctrough at W8. In multivariate analysis, SVR24 remained associated with response to previous HCV treatment [non-responders versus null responders: OR=5.0(1.3-20.0); relapsers vs. null responders: OR=28.8(4.9-169.5)]. HCV treatment was discontinued for adverse events in 17% of patients. A 51% decrease in ATV/r-AUC0-8 h (p<0.01) and a 57% increase in RAL-AUC0-8 h (p<0.01) were observed, although atazanavir/r or raltegravir did not affect BOC-AUC0-8 h significantly. The ATV mean Cthrough fell from 763.8 ng/mL (CI 95%: 230.3-1297.3) without BOC to 507.7 ng/mL (CI 95%: 164-851.4) with BOC.

CONCLUSIONS

Boceprevir-based regimen demonstrated a high SVR24 rate in treatment-experienced HIV-HCV genotype-1-coinfected relapsers.

Role of therapeutic drug monitoring in pulmonary infections: use and potential for expanded use of dried blood spot samples

Respiratory tract infections are among the most common infections in men. We reviewed literature to document their pharmacological treatments, and the extent to which therapeutic drug monitoring (TDM) is needed during treatment. We subsequently examined potential use of dried blood spots as sample procedure for TDM. TDM was found to be an important component of clinical care for many (but not all) pulmonary infections. For gentamicin, linezolid, voriconazole and posaconazole dried blood spot methods and their use in TDM were already evident in literature. For glycopeptides, β-lactam antibiotics and fluoroquinolones it was determined that development of a dried blood spot (DBS) method could be useful. This review identifies specific antibiotics for which development of DBS methods could support the optimization of treatment of pulmonary infections.

Ribavirin and abacavir drug interaction in HIV-HCV coinfected patients: fact or fiction?

OBJECTIVE(S)

To examine the impact of ribavirin and abacavir coadministration on hepatitis C virus (HCV) virological response and trough ribavirin plasma concentration (Cmin) in HIV-HCV coinfected patients.

DESIGN

Pharmacokinetic substudy on patients from the ANRS CO-13 HEPAVIH cohort.

METHODS

Patients receiving ribavirin-pegylated interferon for whom a ribavirin steady state Cmin was prospectively determined were included. Rapid virological response (RVR), early virological response (EVR) and sustained virological response (SVR) as well as HCV-RNA decline were evaluated.

RESULTS

Overall, 124 HIV-HCV coinfected patients (95% on antiretroviral therapy) were enrolled. Of these patients, 22% received abacavir. The overall median (interquartile range) ribavirin Cmin was 1.6 mg/l (1.2-2.2) with no statistical difference between abacavir users and nonusers [1.5 mg/l (0.99-2.1) and 1.7 (1.2-2.3), P = 0.15]. RVR and EVR were 52 and 72%, respectively. There was no difference observed in the proportion of abacavir users vs. nonusers achieving RVR (respectively 59 vs. 50%, P = 0.40) or EVR (72 vs. 73%, P = 0.94), or in the HCV-RNA decline at week 4 [-2.24 log(10) IU/ml, (-3.58; -0.81) and -1.27 (-2.8; -0.47) P = 0.28] or at week 12 [-1.76 log(10) IU/ml (-3.67; -0.35) and -1.85 (-3.13; -1.13) (P = 0.58)]. The SVR rate was 45% for abacavir users and 24% for abacavir nonusers, but the difference was not statistically significant (P = 0.059).

CONCLUSION

In our study, there was no evidence that abacavir affected HCV treatment outcomes and the ribavirin Cmin was similar in abacavir users and nonusers, confirming the absence of pharmacokinetic interaction between abacavir and ribavirin. An abacavir-containing regimen is, therefore, a well tolerated treatment alternative for coinfected patients starting HCV treatment.