Simultaneous determination of rifampicin, clarithromycin and their metabolites in dried blood spots using LC-MS/MS

Introduction: Rifampicin (RIF) and clarithromycin (CLR) are common drugs for the treatment of infections like Mycobacterium tuberculosis and Mycobacterium ulcerans. Treatment for these diseases are long-term and the individual pharmacokinetic variation, drug-drug interactions or non-adherence may introduce sub-therapeutic exposure or toxicity. The application of therapeutic drug monitoring (TDM) can be used to ensure efficacy and avoid toxicity. With the use of dried blood spot (DBS), TDM may be feasible in rural areas. During DBS method development, unexpected interactions or matrix effects may be encountered due to endogenous components in the blood. Another complication compared to plasma analysis is that RIF can form chelate complexes with ferric ions or can bind with hemes, which are potentially present in the extracts of dried blood spots. Methods: The investigation focused on the interaction between RIF and the endogenous components of the DBS. The use of ethylenediaminetetraacetic acid (EDTA) and deferoxamine (DFX) as chelator agents to improve recoveries and matrix effects were investigated. A rapid analytical method was developed and validated to quantify RIF and CLR and their active metabolites desacetyl rifampicin (DAc-RIF) and 14-hydroxyclatythromcin (14OH-CLR) in DOS samples. A clinical application study was performed in tuberculosis patients by comparing DBS concentrations with plasma concentrations. Results: The interaction between RIF and the DBS matrix was avoided using the complexing agents EDTA and DFX, which improved recoveries and matrix effects. The developed sample procedure resulted in a simple and fast method for the simultaneous quantification of RIF, CLR and their metabolites in DOS samples. High stability was observed as all four substances were stable at ambient temperature for 2 months. Deming regression analysis of the clinical application study showed no significant differences for RIF, DAc-RIF, CLR and 14OH-CLR between patient plasma and DBS analysis. The slopes of the correlation lines between DBS and plasma concentrations of RIF, DAc-RIF, CLR and 14OH-CLR were 0.90, 0.99, 0.80 and 1.09 respectively. High correlations between plasma and DBS concentrations were observed for RIF (R-2=0.9076), CLR (R-2=0.9752) and 14OH-CLR (R-2=0.9421). Lower correlation was found for DAc-RIF (R-2 of 0.6856). Conclusion: The validated method is applicable for TDM of RIF, CLR and their active metabolites. The stability of the DBS at high temperatures can facilitate the TDM and pharmacokinetic studies of RIF and CLR even in resource limited areas. The role of EDTA and DFX as complexing agents in the extraction was well investigated and may provide a solution for potential applications to other DBS analytical methods. (C) 2013 Elsevier B.V. All rights reserved

Limited-sampling strategies for anidulafungin in critically ill patients

Efficacy of anidulafungin is driven by the area under the concentration-time curve (AUC)/MIC ratio. Determination of the anidulafungin AUC along with MIC values can therefore be useful. Since obtaining a full concentration-time curve to determine an AUC is not always feasible or appropriate, limited-sampling strategies may be useful in adequately estimating exposure. The objective of this study was to develop a model to predict the individual anidulafungin exposure in critically ill patients using limited-sampling strategies. Pharmacokinetic data were derived from 20 critically ill patients with invasive candidiasis treated with anidulafungin. These data were used to develop a two-compartment model in MW\Pharm using an iterative 2-stage Bayesian procedure. Limited- sampling strategies were subsequently investigated using two methods, a Bayesian analysis and a linear regression analysis. The best possible strategies for these two methods were evaluated by a Bland-Altman analysis for correlation of the predicted and observed AUC from 0 to 24 h (AUC(0-24)) values. Anidulafungin exposure can be adequately estimated with the concentration from a single sample drawn 12 h after the start of the infusion either by linear regression (R-2 = 0.99; bias, 0.05%; root mean square error [RMSE], 3%) or using a population pharmacokinetic model (R-2 = 0.89; bias, -0.1%; RMSE, 9%) in critically ill patients and also in less severely ill patients, as reflected by healthy volunteers. Limited sampling can be advantageous for future studies evaluating the pharmacokinetics and pharmacodynamics of anidulafungin and for therapeutic drug monitoring in selected patients

The influence of the dried blood spot drying time on the recoveries of six immunosuppressants

Investigation of the drying time of dried blood spots (DBS) is currently not included in DBS validations. The influence of the DBS drying time on the recovery of tacrolimus, ascomycin, sirolimus, everolimus, cyclosporin A and temsirolimus was evaluated by measuring DBS with a fixed blood volume at a hematocrit range between 0.1 and 0.6 L/L at 3, 24 and 48 hours of drying time. Results showed that the recovery of sirolimus, everolimus, temsirolimus and cyclosporin A was influenced by the DBS drying time, while the recovery of tacrolimus and ascomycin was not. A drying time of at least 24 hours is advised in order to stabilize hematocrit and concentration related recovery effects of sirolimus, everolimus, temsirolimus and cyclosporin A

Antidepressants self-poisoning and ICU admissions in a University Hospital in the Netherlands

Objectives: Many overdosed patients are admitted to an ICU. Antidepressants are frequently used. We examined clinical end-points of toxicity recorded during admission to our ICU of all antidepressants used in overdose. Design: Single centre; retrospective analysis, 5 consecutive years (1994 - 1998). Setting: Intensive and Respiratory Care Unit, Groningen University Hospital. Participants: 86 patients admitted to the ICU because of antidepressant self-poisoning - database of 258 consecutively admitted patients with (auto-)intoxication. Results: Significantly more patients were intoxicated with TCAs (65) compared with SSRIs (20; p <0.05), despite the fact that the number of prescriptions of antidepressants in the community was greater for SSRIs than for TCAs. Patients intoxicated with TCAs needed significantly more often tracheal intubation (27/65 vs 7/20; p <0.05), and these individuals had also significantly more often tachycardia (14 vs. 3) and QRS-complex widening (19 vs. 1), compared to those with non-TCA antidepressant intoxication (p <0.05). Conclusions: TCA self-poisoning has remained the predominant cause of morbidity among patients with auto-intoxication admitted to our ICU in the previous years. The data from this ICU-population confirm previous evidence that SSRIs are safer in overdose than TCAs. This finding was not explained by more prescriptions in the community of TCAs compared with SSRIs. Physicians should be more reluctant in prescribing TCAs to depressed patients in whom the risk of self-poisoning is difficult to assess

Efficacy of a new pulmonary cyclosporine a powder formulation for prevention of transplant rejection in rats

Background: The aim of this pilot study was to determine the pharmacokinetics of cyclosporine A powder for inhalation (iCsA) and its rejection prevention efficacy in an experimental lung transplantation model in rats. Methods: Single-dose pharmacokinetics (10 mg/kg) of pulmonary and orally administered cyclosporine A was determined in whole blood and in lung and kidney tissue. The efficacy of iCsA (2.5 and 5 mg/kg) in inhibiting rejection was determined in an orthotopic left-lung transplantation rat model and compared with orally administered CsA (5 and 10 mg/kg). The ventilation score of lung allografts was assessed with roentgenograms. At Day 10 post-operatively, the rats were terminated and lungs were prepared for histologic analysis. Results: In the pharmacokinetics study, AUC(0-48) values in blood for iCsA and oral CsA were similar (47,790 +/- 1,739 and 46,987 +/- 2,439 ng h ml(-1), respectively). In contrast, iCsA levels in lung tissue were much higher than oral CsA levels (AUC: 9,152,977 +/- 698,920 vs 84,149 +/- 8,134 ng h g(-1), respectively), showing the effectiveness of the pulmonary administration. In the rejection study, non-treated animals showed complete rejection after 8 days according to roentgenography. Treatment with 5 mg/kg iCsA reduced rejection on Day 10, whereas the 2.5-mg/kg dose did not inhibit rejection. Oral CsA at 10 mg/kg reduced rejection, whereas the 5-mg/kg dose showed hardly any effect on rejection. Conclusions: We found that iCsA is an effective immunosuppressive formulation, and may become a valuable asset for clinical use in combination with systemic immunosuppression. J Heart Lung Transplant 2009;28:486-92. Copyright (C) 2009 by the International Society for Heart and Lung Transplantation

Rosiglitazone attenuates transplant arteriosclerosis after allogeneic aorta transplantation in rats

BACKGROUND. Transplant arteriosclerosis is a leading cause of chronic transplant dysfunction and is characterized by occlusive neointima formation in intragraft arteries. Development of transplant arteriosclerosis is refractory to conventional immunosuppressive drugs and adequate therapy is not available. In this study, we determined the efficacy of the synthetic peroxisome proliferator-activated receptor (PPAR)-γ agonist rosiglitazone to attenuate the development of transplant arteriosclerosis in rat aortic allografts. METHODS. Lewis aortic allografts were transplanted into Brown Norway recipient rats. Recipient rats received either ∼5 mg rosiglitazone/day (starting 1 week before transplantation until the end of the experiment) or were left untreated. Transplant arteriosclerosis was quantified using morphometric analysis. Alloreactivity was measured in vitro using mixed lymphocyte reactions. Regulatory T cell frequency and function were analyzed using flow cytometry and in vitro suppression assays, respectively. Intragraft gene expression was analyzed using real-time polymerase chain reaction. Finally, medial and neointimal vascular smooth muscle cell proliferation was analyzed in vitro. RESULTS. Rosiglitazone significantly reduced transplant arteriosclerosis development 8 weeks after transplantation (P&lt;0.01 vs. nontreated). Rosiglitazone reduced T cell alloreactivity which was not mediated through modulation of CD4CD25FoxP3 regulatory T cells. Reduced development of transplant arteriosclerosis coincided with reduced intragraft expression of stromal-derived factor-1α and platelet-derived growth factor receptor-β. Finally, rosiglitazone reduced growth-factor-driven proliferation of both medial and neointimal vascular smooth muscle cells in vitro, which was not mediated through PPARγ. CONCLUSION. PPARγ agonists may offer a new therapeutic strategy in clinical transplantation to attenuate the development of transplant arteriosclerosis and thereby chronic transplant dysfunction.</p