Docetaxel is an antineoplastic agent that acts by disrupting the microtubular network in cells that is essential for mitotic and interphase cellular functions. Docetaxel binds to free tubulin and promotes the assembly of tubulin into stable microtubules while simultaneously inhibiting their disassembly. This leads to the production of microtubule bundles without normal function and to the stabilization of microtubules, which results in the inhibition of mitosis in cells. Docetaxel's binding to microtubules does not alter the number of protofilaments in the bound microtubules, a feature which differs from most spindle poisons currently in clinical use.
Absorption
The pharmacokinetics of docetaxel has been evaluated in cancer patients after administration of 20 mg/m2 to 115 mg/m2 in phase 1 studies. The area under the curve (AUC) was dose proportional following doses of 70 mg/m2 to 115 mg/m2 with infusion times of 1 to 2 hours.
Docetaxel’s pharmacokinetic profile is consistent with a three-compartment pharmacokinetic model, with initial rapid distribution phase and the late (terminal) phase.
Distribution
Mean steady state volume of distribution was 113 L. Docetaxel is approximately 94% protein bound in vitro, mainly to α1-acid glycoprotein, albumin, and lipoproteins. In three cancer patients, the in vitro binding to plasma proteins was approximately 97%. Dexamethasone does not affect the protein binding of docetaxel.
Elimination
With extended plasma sampling up to 8 to 22 days post infusion, the estimated mean total body clearance was 18 L/h/m2 (range of means: 14 to 23) and mean terminal elimination half-life was 116 hours (range of means: 92 to 135).
Metabolism
Docetaxel is metabolized by the CYP3A4 isoenzyme in vitro [see Drug Interactions (7)].
Excretion
In three cancer patients urinary and fecal excretion accounted for approximately 6% and 75% of the administered radioactivity, respectively, within 7 days. About 80% of the radioactivity recovered in feces was excreted during the first 48 hours as 1 major and 3 minor metabolites with less than 8% as unchanged drug.
Specific Populations
Effect of Age
A population pharmacokinetic analysis was carried out after docetaxel treatment of 535 patients dosed at 100 mg/m2. Pharmacokinetic parameters estimated by this analysis were very close to those estimated from phase 1 studies. The pharmacokinetics of docetaxel was not influenced by age.
Effect of Gender
The population pharmacokinetics analysis described above also indicated that gender did not influence the pharmacokinetics of docetaxel.
Hepatic Impairment
The population pharmacokinetic analysis described above indicated that in patients with clinical chemistry data suggestive of mild to moderate liver impairment (AST and/or ALT >1.5 times ULN concomitant with alkaline phosphatase >2.5 times ULN), total body clearance was lowered by an average of 27%, resulting in a 38% increase in systemic exposure (AUC). This average, however, includes a substantial range and there is, at present, no measurement that would allow recommendation for dose adjustment in such patients. Patients with combined abnormalities of transaminase and alkaline phosphatase should not be treated with Docetaxel Injection. Patients with severe hepatic impairment have not been studied [see Warnings and Precautions (5.2), Use in Specific Populations (8.6)].
Drug Interaction Studies
Effect of Ketoconazole
The effect of ketoconazole (a strong CYP3A4 inhibitor) on the pharmacokinetics of docetaxel was investigated in 7 cancer patients. Patients were randomized to receive either docetaxel (100 mg/m2 intravenous) alone or docetaxel (10 mg/m2 intravenous) in combination with ketoconazole (200 mg orally once daily for 3 days) in a crossover design with a 3-week washout period. The results of this study indicated that the mean dose-normalized AUC of docetaxel was increased 2.2-fold and its clearance was reduced by 49% when docetaxel was coadministered with ketoconazole [see Dosage and Administration (2.7), Drug Interactions (7)].
Effect of Combination Therapies
Docetaxel is an antineoplastic agent that acts by disrupting the microtubular network in cells that is essential for mitotic and interphase cellular functions. Docetaxel binds to free tubulin and promotes the assembly of tubulin into stable microtubules while simultaneously inhibiting their disassembly. This leads to the production of microtubule bundles without normal function and to the stabilization of microtubules, which results in the inhibition of mitosis in cells. Docetaxel's binding to microtubules does not alter the number of protofilaments in the bound microtubules, a feature which differs from most spindle poisons currently in clinical use.
Absorption
The pharmacokinetics of docetaxel has been evaluated in cancer patients after administration of 20 mg/m2 to 115 mg/m2 in phase 1 studies. The area under the curve (AUC) was dose proportional following doses of 70 mg/m2 to 115 mg/m2 with infusion times of 1 to 2 hours.
Docetaxel’s pharmacokinetic profile is consistent with a three-compartment pharmacokinetic model, with initial rapid distribution phase and the late (terminal) phase.
Distribution
Mean steady state volume of distribution was 113 L. Docetaxel is approximately 94% protein bound in vitro, mainly to α1-acid glycoprotein, albumin, and lipoproteins. In three cancer patients, the in vitro binding to plasma proteins was approximately 97%. Dexamethasone does not affect the protein binding of docetaxel.
Elimination
With extended plasma sampling up to 8 to 22 days post infusion, the estimated mean total body clearance was 18 L/h/m2 (range of means: 14 to 23) and mean terminal elimination half-life was 116 hours (range of means: 92 to 135).
Metabolism
Docetaxel is metabolized by the CYP3A4 isoenzyme in vitro [see Drug Interactions (7)].
Excretion
In three cancer patients urinary and fecal excretion accounted for approximately 6% and 75% of the administered radioactivity, respectively, within 7 days. About 80% of the radioactivity recovered in feces was excreted during the first 48 hours as 1 major and 3 minor metabolites with less than 8% as unchanged drug.
Specific Populations
Effect of Age
A population pharmacokinetic analysis was carried out after docetaxel treatment of 535 patients dosed at 100 mg/m2. Pharmacokinetic parameters estimated by this analysis were very close to those estimated from phase 1 studies. The pharmacokinetics of docetaxel was not influenced by age.
Effect of Gender
The population pharmacokinetics analysis described above also indicated that gender did not influence the pharmacokinetics of docetaxel.
Hepatic Impairment
The population pharmacokinetic analysis described above indicated that in patients with clinical chemistry data suggestive of mild to moderate liver impairment (AST and/or ALT >1.5 times ULN concomitant with alkaline phosphatase >2.5 times ULN), total body clearance was lowered by an average of 27%, resulting in a 38% increase in systemic exposure (AUC). This average, however, includes a substantial range and there is, at present, no measurement that would allow recommendation for dose adjustment in such patients. Patients with combined abnormalities of transaminase and alkaline phosphatase should not be treated with Docetaxel Injection. Patients with severe hepatic impairment have not been studied [see Warnings and Precautions (5.2), Use in Specific Populations (8.6)].
Drug Interaction Studies
Effect of Ketoconazole
The effect of ketoconazole (a strong CYP3A4 inhibitor) on the pharmacokinetics of docetaxel was investigated in 7 cancer patients. Patients were randomized to receive either docetaxel (100 mg/m2 intravenous) alone or docetaxel (10 mg/m2 intravenous) in combination with ketoconazole (200 mg orally once daily for 3 days) in a crossover design with a 3-week washout period. The results of this study indicated that the mean dose-normalized AUC of docetaxel was increased 2.2-fold and its clearance was reduced by 49% when docetaxel was coadministered with ketoconazole [see Dosage and Administration (2.7), Drug Interactions (7)].
Effect of Combination Therapies
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