Gemcitabine, epirubicin and paclitaxel: pharmacokinetic and pharmacodynamic interactions in advanced breast cancer.
BACKGROUND
The objectives of this study were to investigate the disposition of gemcitabine, epirubicin, paclitaxel, 2',2'-difluorodeoxyuridine and epirubicinol, and characterize the pharmacokinetic and pharmacodynamic profile of treatment in patients with breast cancer.


METHODS
The drug dispostion in 15 patients who received gemcitabine 1000 mg/m2, epirubicin 90 mg/m2 and paclitaxel 175 mg/m2 (GEP) on day 1 of a 21-day cycle, was compared with that of patients treated with epirubicin 90 mg/m2 and paclitaxel 175 mg/m2 (EP, n = 6) and epirubicin 90 mg/m2 alone (n = 6). Drug and metabolite levels in plasma and urine were assessed by high-performance liquid chromatography and parameters of drug exposure were related to hematological toxicity by a sigmoid-maximum effect (Emax) model.


RESULTS
Paclitaxel administration significantly increased the epirubicinol area under the concentration-time curve, from 357+/-146 (epirubicin) to 603+/-107 (EP) and 640+/-81 h x ng/ml (GEP), and reduced the renal clearance of epirubicin and epirubicinol by 38 and 52.2% and 34.5 and 53% in GEP- and EP-treated patients, respectively, compared with epirubicin alone. Gemcitabine had no apparent effect on paclitaxel and epirubicin pharmacokinetics, and renal clearance of epirubicin and epirubicinol. The only pharmacokinetic/pharmacodynamic relationship observed was between neutropenia and the time spent above the threshold plasma level of 0.1 micromol/l (tC0.1) of paclitaxel, with the time required to obtain a 50% decrease in neutrophil count (Et50) of GEP being 7.8 h, similar to that of EP.


CONCLUSIONS
Paclitaxel and/or its vehicle, Cremophor EL, interferes with the disposition and renal excretion of epirubicin and epirubicinol; gemcitabine has no affect on epirubicin and paclitaxel plasma pharmacokinetics and renal excretion of epirubicin, while neutropenia is not enhanced by gemcitabine.
Fogli
S
S
Department of Oncology, Transplants and Advanced Technologies in Medicine, University of Pisa, Italy.
Danesi
R
R
Gennari
A
A
Donati
S
S
Conte
P F
PF
Del Tacca
M
M
D000328:Adult; D000704:Analysis of Variance; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000008:administration & dosage* / Q000493:pharmacokinetics*; D001707:Biopsy, Needle; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology; D003841:Deoxycytidine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004347:Drug Interactions; D015251:Epirubicin / Q000008:administration & dosage / Q000493:pharmacokinetics; D005260:Female; D006801:Humans; D008875:Middle Aged; D009367:Neoplasm Staging; D017239:Paclitaxel / Q000008:administration & dosage / Q000493:pharmacokinetics; D011336:Probability; D011379:Prognosis; D016896:Treatment Outcome; D000093542:Gemcitabine
D003841:Deoxycytidine; D015251:Epirubicin; D017239:Paclitaxel; D000093542:Gemcitabine