Serena Fucile

Linezolid plasma concentrations and occurrence of drug-related haematological toxicity in patients with Gram-positive infections

Retrospective studies have documented a significant association between linezolid (LNZ) plasma concentrations and drug-related haematological toxicity. However, the safe upper threshold level for LNZ plasma trough concentrations (Cmin values) has not been defined with certainty. A prospective observational study was performed aimed at comparing LNZ Cmin values in patients developing drug-related side effects with those measured in patients not experiencing LNZ toxicity. LNZ Cmin values were measured from the first week after starting therapy and were repeated periodically up to the end of treatment. Fifty patients, for a total of 210 LNZ Cmin evaluations, were considered. All patients (n=9) who developed drug-related haematological toxicity also had significantly higher plasma LNZ Cmin values during the first week of therapy (9.0±6.4 mg/L vs. 4.9±3.7 mg/L; P<0.01) and thereafter (9.3±5.4 mg/L vs. 4.4±3.4 mg/L; P<0.01). The significant association between LNZ plasma concentrations and haematological toxicity was also confirmed by multivariate logistic regression analysis including age, serum creatinine and concomitant medications as independent variables. A causal relationship between LNZ concentrations and the risk of developing drug-related haematological toxicity was observed. Accordingly, application of therapeutic drug monitoring may improve the safety outcome of patients receiving LNZ therapy.

Inter- and intra-patient variability of raltegravir pharmacokinetics in HIV-1-infected subjects

OBJECTIVES Limited studies in healthy volunteers and in HIV-1-infected patients have shown that raltegravir pharmacokinetics are characterized by high inter-patient variability. Only scanty data are, however, available on intra-patient raltegravir variability. The present study was designed to evaluate in parallel the inter- and intra-patient variability of raltegravir pharmacokinetics in HIV-1-infected patients during routine therapeutic drug monitoring (TDM). METHODS Fifteen HIV-infected patients treated with highly active antiretroviral therapy containing 400 mg of raltegravir twice daily were included in the study. Pharmacokinetic evaluations were performed during two consecutive visits. Only patients given raltegravir for at least 1 month and with no changes in antiretroviral and concomitant therapy between the two pharmacokinetic evaluations were considered. Raltegravir plasma concentrations were determined by a validated HPLC method. Blood samples were collected at 0, 1, 2, 3 and 4 h after the morning drug dose. Raltegravir AUC(0-12) was estimated using a recently developed algorithm. RESULTS The pharmacokinetic evaluation was repeated after an average of 52 ± 68 days. Raltegravir AUC(0-12) values ranged from 1495 to 49 051 ng · h/mL. The main finding was that intra-patient variability was a large component of the overall variability in raltegravir pharmacokinetics. In some instances the difference between raltegravir AUC(0-4) and AUC(0-12) measured in the same patient during two consecutive evaluations exceeded 110% and 75%, respectively. CONCLUSIONS The pharmacokinetics of raltegravir in HIV-1-infected subjects are characterized not only by inter-patient variability but also by high intra-patient variability. This condition limits the application of TDM for raltegravir, and might potentially affect patient outcome.

Different effects of PCB101, PCB118, PCB138 and PCB153 alone or mixed in MCF-7 breast cancer cells

Polychlorinated biphenyls (PCBs) are ubiquitous, persistent environmental contaminants that can be a potential health hazard. In the present study we analyzed the potential estrogenic effect in MCF-7 cells of four biologically relevant PCB congeners, alone or in mixtures, present in dairy products, vegetable oil and fish: PCB101, PCB118, PCB138 and PCB153. The mixture of four PCB was tested at seven different concentrations. We investigated the ability of these PCBs, alone or mixed, to induce cell proliferation, and the level of estrogen-regulated protein pS2, in human MCF-7 breast cancer cells. PCB153 (35 microM) stimulated cell proliferation from 48 h up to day 6, PCB118 (40 microM) only at 48 h, but PCB101 (45 microM) and PCB138 (15 microM) applied to the cells for 6 days had no effect. In contrast, the various concentrations of mixtures significantly reduced cell proliferation at different times. No change in pS2 levels was seen after treatment with the PCBs alone or mixed. In exploring the mechanism of these events, we found that PCB153 induced mitogen-activated protein kinase (MAPK) ERK1/2 at 4, 8 and 12 h, while the antiproliferative effect seemed to be related to an apoptotic action beginning at 12 h and ending at 48 h. These findings indicate that these PCBs alone or mixed have no estrogenic effect in MCF-7 cells, although PCB153 induce an ERK1/2-mediated mitogenic effect. On the contrary the mixture of PCBs induces an antiproliferative effect, ascribable to an apoptotic action.

Low Body Weight in Females Is a Risk Factor for Increased Tenofovir Exposure and Drug-Related Adverse Events

Treatment with tenofovir sometimes leads to non-reversible kidney and/or bone diseases. Factors associated with these drug-related adverse events are poorly characterized. Our objective was to investigate such factors in patients treated long term with daily tenofovir. One-hundred Caucasian HIV-positive patients with basal creatinine clearance >80 mL/min treated with tenofovir for at least 6 months and with at least one assessment of tenofovir plasma trough concentrations were considered. Tenofovir-associated adverse events were defined as the appearance of pathological proteinuria, worsening of renal function or bone demineralization. By multivariate regression analysis, we found that serum creatinine (p = 0.003) and body weight (p = 0.002) were the factors independently associated with plasma tenofovir concentrations. In particular, women with body weight<50 kg had significantly higher plasma tenofovir concentrations than those weighting >50 Kg (160±93 vs.71±52 ng/mL, p<0.001). High tenofovir plasma trough concentrations and the age of the patients were independently associated with the development of drug-related kidney and bone toxicity. In this retrospective study we have shown that HIV-infected women with low body weight are at risk to be exposed to high tenofovir plasma trough concentrations, ultimately resulting in a significant hazard to develop long-term tenofovir complications.

Comparison of the In Vivo Pharmacokinetics and In Vitro Dissolution of Raltegravir in HIV Patients Receiving the Drug by Swallowing or by Chewing

ABSTRACT The pharmacokinetics of raltegravir (RAL) in HIV patients is characterized by high interpatient/intrapatient variability. We investigated the potential contribution of the drug pharmaceutical formulation to RAL pharmacokinetics. We first compared in vivo the pharmacokinetics of RAL for 67 patients to whom the drug was administered by swallowing the intact tablet with those obtained from 13 HIV-infected patients who chewed the RAL tablet due to swallowing difficulties. Subsequently, we evaluated in vitro the dissolution of RAL tablets under different conditions. In the in vivo study, we found that patients given RAL by chewing the tablets presented pharmacokinetic profiles characterized by significantly higher RAL absorption than did patients receiving the drug by swallowing. The in vitro studies showed that when the whole tablets were exposed to an acidic medium, the release of RAL was very low, whereas when the tablets were crushed, the profiles presented significantly higher concentrations of RAL. Crushed tablets tested in water or in a pH 6.8 buffer exhibited prompt and complete dissolution of RAL. HIV-infected patients receiving RAL by chewing the tablet showed higher drug absorption and reduced pharmacokinetic variability compared with patients swallowing the intact tablet. This is related to problems in tablet disintegration and to erratic drug absorption. The amelioration of the RAL pharmaceutical formulation could improve drug pharmacokinetics.

Co-administration of raltegravir reduces daily darunavir exposure in HIV-1 infected patients.

The potential drug-to-drug interaction between darunavir and raltegravir in the setting of HIV infection is a highly debated issue still unresolved. In the present study we have evaluated the pharmacokinetics of darunavir and ritonavir in 53 HIV-1 infected patients with or without concomitant raltegravir administration. The assessment of trough plasma drug concentrations was carried out in all subjects and the potential influence of raltegravir on darunavir and ritonavir disposition, assessed by specific pharmacokinetic evaluations in a subgroup of 25 patients. No significant differences on darunavir and ritonavir plasma trough levels were observed between patients receiving or not raltegravir. Co-administration of raltegravir was, however, associated with a 40% reduction in darunavir C(max) and estimated AUC(0-24), as well a 60% increase in the estimated darunavir clearance compared with values measured in patients not given raltegravir. Notably, this interaction was independent of the dosage of darunavir and not due to effects of raltegravir on the pharmacokinetics of ritonavir. These results should be taken into account when darunavir-based regimens are implemented in the setting of HIV, especially considering that this drug is usually administered at fixed daily dose and no therapeutic drug monitoring is performed in most centres.

Limited Sampling Strategies for the Estimation of Raltegravir Daily Exposure in HIV‐Infected Patients

Stepwise multiple regression analyses were applied to 50 raltegravir pharmacokinetic profiles from 50 HIV patients with the goal to identify limited sampling strategies for the prediction of drug area under the time—concentration curve (AUC0–12). Raltegravir single sampling point‐based equations failed to reliably predict daily drug exposure. Conversely, different algorithms based on few samples and associated with good correlation, acceptable bias, and imprecision with the measured raltegravir AUC0–12 were identified. These models could used to predict raltegravir exposure for clinic or research purposes.

Combined isosorbide dinitrate and ibuprofen as a novel therapy for muscular dystrophies: evidence from Phase I studies in healthy volunteers.

We designed two Phase I studies that assessed healthy volunteers in order to evaluate the safety and to optimize the dosing of the combination of the drugs isosorbide dinitrate, a nitric oxide donor, and ibuprofen, a nonsteroidal antiinflammatory drug. We designed these studies with the aim of designing a Phase II trial to evaluate the drugs’ efficacy in patients affected by Duchenne muscular dystrophy. For the first trial, ISOFEN1, a single-dose, randomized-sequence, open-label, active control, three-treatment cross-over study, was aimed at comparing the pharmacokinetics of ibuprofen 200 mg and isosorbide dinitrate 20 mg when given alone and concomitantly. The pharmacokinetics of ibuprofen given alone versus ibuprofen given concomitantly with isosorbide dinitrate were similar, as documented by the lack of statistically significant differences in the main drug’s pharmacokinetic parameters (time to maximal concentration [Tmax], maximal concentration [Cmax], area under the curve [AUC]0–t, and AUC0–∞). Similarly, we found that the coadministration of ibuprofen did not significantly affect the pharmacokinetics of isosorbide dinitrate. No issues of safety were detected. The second trial, ISOFEN2, was a single-site, dose titration study that was designed to select the maximum tolerated dose for isosorbide dinitrate when coadministered with ibuprofen. Eighteen out of the 19 enrolled subjects tolerated the treatment well, and they completed the study at the highest dose of isosorbide dinitrate applied (80 mg/day). One subject voluntarily decided to reduce the dose of isosorbide dinitrate from 80 mg to 60 mg. The treatment-related adverse events recorded during the study were, for the large majority, episodes of headache that remitted spontaneously in 0.5–1 hour – a known side effect of isosorbide dinitrate. These studies demonstrate that the combination of isosorbide dinitrate and ibuprofen does not lead to pharmacokinetic interactions between the two drugs; they also demonstrate that the combination of isosorbide dinitrate and ibuprofen has optimal tolerability and safety profiles that are similar to those previously reported for isosorbide dinitrate and ibuprofen given alone.

Is it time to revise antiretrovirals dosing? a pharmacokinetic viewpoint.

We document our experience with therapeutic drug monitoring (TDM) of antiretroviral agents (1807 determinations) carried out as day-by-day clinical practice for the optimization of drug dosing in HIV-infected patients. A significant proportion of patients had lopinavir, atazanavir and nevirapine trough concentrations exceeding the upper therapeutic threshold. Further studies are needed to identify good candidates/drugs for TDM, eventually allowing the selection of patients who may benefit from TDM-driven adjustments in antiretrovirals dosage.

Lights and shadows of the actual European guidelines on bioanalytical method validation: the case of raltegravir.

Background: Recently, the European Medicines Agency (EMA) has released new guidelines on the validation of bioanalytical methods. In this work, we compared the analytical performance of 2 high-performance liquid chromatography with tandem mass spectrometry methods designed for the quantification of the antiretroviral drug raltegravir (RAL) that fully accomplish the criteria according to the new EMA guidelines. Methods: The first method was developed with the goal of separating RAL from its main metabolite, whereas in the second method, we deliberately did not discriminate the parent drug from its metabolite. After validation, both methods were used for the quantification of plasma samples from HIV-infected patients on RAL-based maintenance antiretroviral therapy. Results: Incurred reanalysis of samples obtained from patients receiving RAL as therapy evidenced optimal performance for both methods. Similarly, the comparison of both methods performed by the Deming test showed that they correlate significantly with each other (Pearson coefficient of regression 0.97, P < 0.0001) with no significant deviation from linearity according to the Cusum test. The Bland–Altman test, however, showed a mean difference between the 2 methods of 54.1% (limits of agreements of ±1.96 SD ranged from −163.3% to +271.5%). Such differences were significantly affected by interindividual variations in the production of RAL metabolites. Conclusions: We conclude that the recently released EMA guidelines on bioanalytical method validation present some limitations related to the process of method development. To have confidence in the drug-concentration measurements, laboratories must demonstrate their performance through the participation in international proficiency testing schemes that must include patient samples.