Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027947 (neutropenia)
 17,527 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Alpha(1)-acid glycoprotein, a plasma protein that binds docetaxel, is a significant determinant of the clearance and activity of docetaxel, but its serum levels in cancer patients are variable. This emphasizes the importance of investigating the pharmacokinetics of unbound drug rather than total drug in the plasma. In the present study, the pharmacokinetics and pharmacodynamics of unbound docetaxel were investigated in cancer patients. Docetaxel was infused over a 1-h period in 69 patients. The concentration of unbound docetaxel was measured in the plasma ultrafiltrate at the end of infusion and the unbound fraction (fu) was calculated. The pharmacokinetics of total docetaxel in the plasma was investigated. The area under the concentration-time curve (AUC) of unbound docetaxel was calculated by multiplying fu by the AUC of total docetaxel. The peak concentration at the end of infusion (Cmax) and AUC of total and unbound drug were compared between patients who did or did not experience grade 4 neutropenia. The median of fu was 4.0%, ranging from 1.2 to 22.6% (5-95% percentile; 1.4-10.5%). Grade 4 neutropenia was observed in 24 patients. Although Cmax and AUC of total drug were not different in patients with or without grade 4 neutropenia, patients who experienced grade 4 neutropenia had significantly greater Cmax (92.3 vs 63.3 ng/mL, P=0.01) and AUC (0.137 vs 0.104 microgxh/mL, P=0.05) of unbound docetaxel. In a logistic regression analysis, the unbound Cmax and alpha1-acid glycoprotein were determinants of grade 4 neutropenia. Pharmacokinetics of unbound drug rather than total drug is a better predictor of neutropenia for docetaxel.
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PMID:Pharmacokinetics and pharmacodynamics of protein-unbound docetaxel in cancer patients. 1654 21

Neutropenia is the main dose-limiting toxicity occurring in docetaxel treatment. The objective of this study was to identify pharmacodynamic (PD) factors responsible for the neutropaenia caused by docetaxel. Data were obtained from 92 patients treated with docetaxel as a monochemotherapy in two different treatment centres. A semiphysiological population pharmacokinetic-pharmacodynamic (PK/PD) model was applied to describe the time course of neutrophils and the neutropaenic effect of docetaxel. The plasma docetaxel concentration was assumed to inhibit the proliferation of neutrophil precursors through a linear model: Drug effect=Slope x Conc. Slope corresponds to the patients' sensitivity to the neutropaenic effect of docetaxel. Covariate analysis was performed by testing the relationship between the patients' characteristics and Slope using the program NONMEM. The neutropaenic effect of docetaxel showed a high interindividual variability. Three significant PD covariates were identified: serum alpha1-acid glycoprotein levels (AAG), level of chemotherapy pretreatment, and treatment centre. Extensive pretreatment was associated with an increase in Slope values meaning a higher haematotoxicity. An increase in AAG was associated with a decrease of both Slope and docetaxel plasma clearance. Patients treated in one centre had both higher Slope and docetaxel clearance. The centre effect (most likely due to a bias in the PK part of the study between the two centres) reveals the robustness of the PK/PD model. Individual dosing of docetaxel should be based on previous chemotherapy but not on the AAG level since it has a similar influence on PD and PK docetaxel parameters. This methodology should be applied to further investigate elderly patients and to identify more precisely the characteristics of previous chemotherapy that contribute to the cumulative myelotoxicity.
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PMID:Clinical pharmacodynamic factors in docetaxel toxicity. 1759 56