A fentanyl patch is widely used for the treatment of cancer pain. Its few adverse effects include constipation and drowsiness. The absorption volume of transdermally applied fentanyl may differ according to its site of application and variability in patch adhesion. Since fentanyl is predominantly metabolized by the drug-metabolizing enzyme cytochrome P450 (CYP) 3A4 in the liver, its concentration may vary in cases of physiologically reduced CYP3A4 activity in the liver (liver disease and aging) or on co-administration of drugs. The clinical significance of measuring plasma concentration of fentanyl is high, but conventional methods require complicated processes such as solid-phase extraction and liquid-liquid extraction before the sample is injected into an HPLC system. In this study, a simple liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for determining plasma fentanyl concentrations by deproteinization with acetonitrile. A recovery test was conducted using an absolute calibration curve to confirm the method's linearity and inter-and intra-day reproducibility. The required plasma volume for detection was reduced from 1 mL in the conventional method to 20 µL in the present study, and a good calibration curve was obtained in the concentration range from 0.05 to 5 ng/mL. These findings suggest that the method for sample preparation and quantification developed in this study are appropriate for measuring fentanyl concentration in human plasma in clinical settings.
The objective of this study was to evaluate the cost-effectiveness of pegfilgrastim (Peg-G) and daily filgrastim (Fil-G) for the primary prophylaxis against febrile neutropenia (FN) in patients with non-Hodgkin lymphoma (NHL) who received cyclophosphamide, vincristine, doxorubicin and prednisolone (CHOP) therapy. We developed a decision analytical model reflecting the clinical processes of NHL patients who received first CHOP therapy. The probabilities at each clinical endpoint were obtained from published sources. To estimate the costs and duration of FN treatment, we analyzed the medical records of NHL patients in hospitals participating in this study. The costs of Peg-G and Fil-G were calculated according to the National Health Insurance drug price list. We assessed an incremental cost-effectiveness ratio (ICER) for a single dose of Peg-G versus 11-days of Fil-G from the perspective of health insurance payers. The sensitivity and robustness of this model were validated by the tornado-diagram and Monte Carlo Method. The costs associated with primary prophylaxis with a single dose of Peg-G and 11-days of Fil-G were 109,628 JPY and 109,243 JPY, respectively. The quality adjusted life years (QALYs) associated with the two strategies were 0.0339 QALYs and 0.0337 QALYs, respectively. The ICER for the Peg-G versus Fil-G was 2,788,571 JPY per QALY. The tornado-diagram revealed that the main influential factors included the cost of Peg-G, number of Fil-G doses, and cost of Fil-G. Monte Carlo simulation revealed an 18.3 probability that Peg-G was cost-effective compared with Fil-G. A single dose of Peg-G was cost-effective compared with 11-days of Fil-G.
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