Docetaxel (Page 7 of 12)

8.6 Hepatic Impairment

Patients with bilirubin >ULN should not receive Docetaxel Injection. Also, patients with AST and/or ALT >1.5 x ULN concomitant with alkaline phosphatase >2.5 x ULN should not receive Docetaxel Injection. [see Boxed Warning, Warnings and Precautions (5.2), Clinical Pharmacology (12.3)].

The alcohol content of Docetaxel Injection should be taken into account when given to patients with hepatic impairment [ see Warnings and Precautions (5.11) ].

10. OVERDOSAGE

There is no known antidote for Docetaxel Injection overdosage. In case of overdosage, the patient should be kept in a specialized unit where vital functions can be closely monitored. Anticipated complications of overdosage include: bone marrow suppression, peripheral neurotoxicity, and mucositis. Patients should receive therapeutic G-CSF as soon as possible after discovery of overdose. Other appropriate symptomatic measures should be taken, as needed.

In two reports of overdose, one patient received 150 mg/m 2 and the other received 200 mg/m 2 as 1-hour infusions. Both patients experienced severe neutropenia, mild asthenia, cutaneous reactions, and mild paresthesia, and recovered without incident.

In mice, lethality was observed following single intravenous doses that were ≥154 mg/kg (about 4.5 times the human dose of 100 mg/m 2 on a mg/m 2 basis); neurotoxicity associated with paralysis, non-extension of hind limbs, and myelin degeneration was observed in mice at 48 mg/kg (about 1.5 times the human dose of 100 mg/m 2 basis). In male and female rats, lethality was observed at a dose of 20 mg/kg (comparable to the human dose of 100 mg/m 2 on a mg/m 2 basis) and was associated with abnormal mitosis and necrosis of multiple organs.

11. DESCRIPTION

Docetaxel is an antineoplastic agent belonging to the taxoid family. It is prepared by semisynthesis beginning with a precursor extracted from the renewable needle biomass of yew plants. The chemical name for docetaxel is (2R,3S)-N-carboxy-3-phenylisoserine,N- tert -butyl ester, 13-ester with 5β-20-epoxy-1,2α,4,7β,10β,13α-hexahydroxytax-11-en-9-one 4-acetate 2-benzoate. Docetaxel has the following structural formula:

Docetaxel Injection
(click image for full-size original)

Docetaxel is a white to off-white powder with an empirical formula of C 43 H 53 NO 14 and a molecular weight of 807.88. It is highly lipophilic and practically insoluble in water.

Two-vial formulation (Injection with Diluent)

Docetaxel Injection USP is a clear yellow to brownish-yellow viscous solution. Docetaxel Injection USP is sterile, non-pyrogenic, and is available in single-dose vials containing 20 mg (0.5 mL) or 80 mg (2 mL) docetaxel anhydrous USP. Each mL contains 40 mg docetaxel anhydrous USP, 60 mg dehydrated alcohol and 1040 mg polysorbate 80. Citric acid (anhydrous) may be used to adjust the pH.

Docetaxel Injection USP requires dilution with Diluent prior to addition to the infusion bag. A sterile, non-pyrogenic, single-dose diluent is supplied for that purpose. The diluent for Docetaxel Injection USP contains 13% polyethylene glycol 400 in water for injection, and is supplied in vials.

One-vial formulation (Injection)

Docetaxel Injection USP is a sterile, non-pyrogenic, pale yellow to brownish-yellow solution at 20 mg/mL concentration.

Each mL contains 20 mg docetaxel anhydrous USP, 4 mg anhydrous citric acid, 520 mg polysorbate 80 and 395 mg dehydrated alcohol solution.

Docetaxel Injection USP is available in single dose and multiple dose vials containing 20 mg (1 mL), 80 mg (4 mL) or 160 mg (8 mL) docetaxel anhydrous USP.

Docetaxel Injection USP requires NO prior dilution with a diluent and is ready to add to the infusion solution.

12. CLINICAL PHARMACOLOGY

12.1 Mechanism of Action

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.

12.3 Human Pharmacokinetics

Absorption: The pharmacokinetics of docetaxel have been evaluated in cancer patients after administration of 20 mg/m 2 to 115 mg/m 2 in phase 1 studies. The area under the curve (AUC) was dose proportional following doses of 70 mg/m 2 to 115 mg/m 2 with infusion times of 1 to 2 hours. Docetaxel’s pharmacokinetic profile is consistent with a three-compartment pharmacokinetic model, with half-lives for the α, β, and γ phases of 4 min, 36 min, and 11.1 hr, respectively. Mean total body clearance was 21 L/h/m 2

Distribution: The initial rapid decline represents distribution to the peripheral compartments and the late (terminal) phase is due, in part, to a relatively slow efflux of docetaxel from the peripheral compartment. Mean steady state volume of distribution was 113 L. In vitro studies showed that docetaxel is about 94% protein bound, mainly to α 1 -acid glycoprotein, albumin, and lipoproteins. In three cancer patients, the in vitro binding to plasma proteins was found to be approximately 97%. Dexamethasone does not affect the protein binding of docetaxel.

Metabolism: In vitro drug interaction studies revealed that docetaxel is metabolized by the CYP3A4 isoenzyme, and its metabolism may be modified by the concomitant administration of compounds that induce, inhibit, or are metabolized by cytochrome P450 3A4 [see Drug Interactions (7)].

Elimination: A study of 14 C-docetaxel was conducted in three cancer patients. Docetaxel was eliminated in both the urine and feces following oxidative metabolism of the tert -butyl ester group, but fecal excretion was the main elimination route. Within 7 days, urinary and fecal excretion accounted for approximately 6% and 75% of the administered radioactivity, respectively. About 80% of the radioactivity recovered in feces is excreted during the first 48 hours as 1 major and 3 minor metabolites with very small amounts (< 8%) of unchanged drug.

Effect of Age: A population pharmacokinetic analysis was carried out after docetaxel treatment of 535 patients dosed at 100 mg/m 2. Pharmacokinetic parameters estimated by this analysis were very close to those estimated from phase 1 studies. The pharmacokinetics of docetaxel were 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) and Use in Specific Populations (8.6) ]

Effect of Race: Mean total body clearance for Japanese patients dosed at the range of 10 mg/m 2 to 90 mg/m 2 was similar to that of European/American populations dosed at 100 mg/m 2 , suggesting no significant difference in the elimination of docetaxel in the two populations.

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/m 2 intravenous) alone or docetaxel (10 mg/m 2 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 co-administration with ketoconazole [see Dosage and Administration (2.7) and Drug-Drug Interactions (7)]

Effect of Combination Therapies:

Dexamethasone: Docetaxel total body clearance was not modified by pretreatment with dexamethasone.
Cisplatin: Clearance of docetaxel in combination therapy with cisplatin was similar to that previously observed following monotherapy with docetaxel. The pharmacokinetic profile of cisplatin in combination therapy with docetaxel was similar to that observed with cisplatin alone.
Cisplatin and Fluorouracil: The combined administration of docetaxel, cisplatin and fluorouracil in 12 patients with solid tumors had no influence on the pharmacokinetics of each individual drug.
Prednisone: A population pharmacokinetic analysis of plasma data from 40 patients with hormone-refractory metastatic prostate cancer indicated that docetaxel systemic clearance in combination with prednisone is similar to that observed following administration of docetaxel alone.
Cyclophosphamide and Doxorubicin: A study was conducted in 30 patients with advanced breast cancer to determine the potential for drug-drug-interactions between docetaxel (75 mg/m 2), doxorubicin (50 mg/m 2), and cyclophosphamide (500 mg/m 2) when administered in combination. The coadministration of docetaxel had no effect on the pharmacokinetics of doxorubicin and cyclophosphamide when the three drugs were given in combination compared to coadministration of doxorubicin and cyclophosphamide only. In addition, doxorubicin and cyclophosphamide had no effect on docetaxel plasma clearance when the three drugs were given in combination compared to historical data for docetaxel monotherapy.

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