This article discusses dried blood spot (DBS) sampling in therapeutic drug monitoring (TDM). The most important advantages of DBS sampling in TDM are the minimally invasive procedure of a finger prick (home sampling), the small volume (children), and the stability of the analyte. Many assays in DBS have been reported in the literature over the previous 5 years. These assays and their analytical techniques are reviewed here. Factors that may influence the accuracy and reproducibility of DBS methods are also discussed. Important issues are the correlation with plasma/serum concentrations and the influence of hematocrit on spot size and recovery. The different substrate materials are considered. DBS sampling can be a valid alternative to conventional venous sampling. However, patient correlation studies are indispensable to prove this. Promising developments are dried plasma spots using membrane and hematocrit correction using the potassium concentration.

Vincristine-induced peripheral neuropathy (VIPN) is a dose-limiting side effect of vincristine (VCR) treatment in children, leading to diminished quality of life. Much remains unknown about the underlying mechanisms of VIPN. This review systematically summarizes the available literature concerning contributing factors of VIPN development in children. Studied factors include patient characteristics, VCR dose, administration method, pharmacokinetics, and genetic factors. Furthermore, this review reports on currently available tools to assess VIPN in children. In total, twenty-eight publications were included. Results indicate that Caucasian race, higher VCR dose, older age and low clearance negatively influence VIPN, although results regarding the latter two factors were rather conflicting. Moreover, genetic pathways influencing VIPN were identified. Furthermore, the studied tools to assess VIPN seriously impairs comparability across study results. Studying the factors and their interactions that seem to influence VIPN in children, should aid in personalized VCR treatment, thereby increasing VCR effectiveness while minimizing toxicity.

Biopsy of the first tumour-draining lymph node (sentinel node, SN) is bound to become the procedure of choice in regional staging of melanoma and breast cancer patients. Several radiopharmaceuticals have been developed for lymphoscintigraphy. In this paper we review the most frequently used radiopharmaceuticals for their appropriateness in the sentinel-node procedure. We conclude that accurate localization of SNs is demonstrated using technetium-99m-sulfur colloid ( 99m Tc-SC), 99m Tc antimony trisulfide colloid ( 99m Tc-ATC) [10] and 99m Tc nanocolloidal albumin ( 99m Tc-CA). 99m Tc-Ca and 99m Tc-SC are both available in Europe. In the United States 99m Tc-SC is the only registered tracer for lymphoscintigraphy & k w d : Key words: Sentinel node -99m Tc-sulfur colloid -99m Tcantimony trisulfide colloid -99m Tc-colloidal albumin -Radiocolloids Eur J Nucl Med (1999) 26 (Suppl): S36-S42

No abstract

In the last few years, an increasing number of dried blood spot (DBS) sampling assays have been developed. With this increase, more insight is gained in the factors that possibly influence the performance of DBS assays. We have developed an assay for four commonly used immunosuppressants; some of them are possibly concomitantly prescribed: cyclosporin A (CsA), tacrolimus (TcR), sirolimus (SiR), and everolimus (EvE). Chromatographic separation from possible ion suppression was obtained within the total runtime of 4.2 min. Trifluoroacetic acid and ammonium acetate were used as mobile phase additives. The linearity ranged from 23.6 to 787, 1.14 to 30.3, 1.34 to 35.8, and 1.26 to 33.7 μg/L, for CsA, TcR, SiR, and EvE, respectively. Between- and within-run accuracy and precision were all within 15 % and extensive validation for DBS samples, such as hematocrit, blood spot volume, and spot punch location was performed. None of these factors were found to be of influence on the performance of the DBS assay.

Plasma concentrations of nilotinib could be predicted on the basis of DBS. DBS sampling to assess nilotinib concentrations in CML patients seems a suitable alternative for venous sampling.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT• The population pharmacokinetics and limited sampling strategies for ciclosporin monitoring have been extensively studied in renal and liver transplant recipients. Little is known about the pharmacokinetics of ciclosporin in patients undergoing haematopoietic allogeneic stem cell transplantation (HSCT).• It is anticipated that there is a difference in pharmacokinetics in patients after kidney or liver transplantation compared with patients undergoing stem cell transplantation, because of mucositis and interacting drugs (e.g. fluconazole).• Data on the pharmacokinetics of ciclosporin and the relationship between its systemic exposure, as reflected by the area under the curve (AUC), and the biological effect as graft vs. host-disease (GVHD) prophylaxis and graft vs. tumour (GVT) response are scarce in patients after HSCT. WHAT THIS STUDY ADDS• A pharmacokinetic model was developed for orally and intravenously administered ciclosporin, enabling an adequate estimate of the systemic exposure of ciclosporin in patients after HSCT. A limited sampling strategy was tested that may serve as a tool to study the optimum systemic exposure (AUC) of ciclosporin in HSCT to prevent GVHD but establish adequate GVT response and to guide therapeutic drug monitoring. AIMTo develop a population pharmacokinetic model of ciclosporin (CsA) in haematopoietic allogeneic stem cell transplantation to facilitate a limited sampling strategy to determine systemic exposure (area under the curve [AUC]), in order to optimize CsA therapy in this patient population. METHODSThe pharmacokinetics of CsA were investigated prospectively in 20 patients following allogeneic haematopoietic stem cell transplantation (HSCT). CsA was given twice daily, as a 3 h i.v. infusion starting at day 1 of the conditioning scheme, and orally later on, when oral intake was well tolerated. Fluconazole was given as antimycotic prophylaxis. Pharmacokinetic parameter estimation was performed using nonlinear mixed effect modelling as implemented in the NONMEM program. A first order absorption model with lag time was compared with Erlang frequency distribution and Weibull distribution models. The influence of demographic variables on the individual empirical Bayesian estimates of clearance and distribution volume was tested. Subsequently two limited sampling strategies (LSS) were evaluated: posterior Bayesian fitting and limited sampling equations. RESULTSTwenty patients were included and 435 samples were collected after i.v. and oral administration of CsA. A two compartment model with first order absorption best described the data. Clearance (CL) was 21.9 l h -1 (relative standard deviation [RSD] Ϯ 5.2%) with an inter-individual variability of 21%. The central volume of distribution (Vc) was 18.3 l (RSD Ϯ 8.7%) with an inter-individual variability of 29%. Bioavailability (F) was 0.71 (RSD Ϯ 9.9%) with and inter-individual variability of 25% and lag time (tlag) was 0.44 h (RSD 5.5%). Weight, body surface area, haematocrit, albumin, ALAT...

99mTc-BIWA 4 can safely be administered to patients with HNSCC, with absence of detectable HAHA responses. The 50-mg dose level showed the highest tumor uptake and tumor to nontumor ratios. These findings support the use of BIWA 4 for RIT studies in patients with HNSCC.