Molecule

Drug Groups

approved; investigational

Description

Docetaxel is a clinically well established anti-mitotic chemotherapy medication used mainly for the treatment of breast, ovarian, and non-small cell lung cancer. Docetaxel binds to microtubules reversibly with high affinity and has a maximum stoichiometry of 1 mole docetaxel per mole tubulin in microtubules.

Indication

For the treatment of patients with locally advanced or metastatic breast cancer after failure of prior chemotherapy. Also used as a single agent in the treatment of patients with locally advanced or metastatic non-small cell lung cancer after failure of prior platinum-based chemotherapy. Lastly, for use, in combination with prednisone, in the treatment of patients with androgen independent (hormone refractory) metastatic prostate cancer.

Pharmacology

Docetaxel is a taxoid antineoplastic agent. It promotes the assembly of microtubules from tubulin dimers and stabilizes microtubules by preventing depolymerization. This stability results in the inhibition of the normal dynamic reorganization of the microtubule network that is essential for vital interphase and mitotic cellular functions. In addition, docetaxel induces abnormal arrays or "bundles" of microtubules throughout the cell cycle and multiple asters of microtubules during mitosis.

Toxicity

Oral LD₅₀ in rat is >2000 mg/kg. Anticipated complications of overdosage include: bone marrow suppression, peripheral neurotoxicity, and mucositis. In two reports of overdose, one patient received 150 mg/m² and the other received 200 mg/m² as 1-hour infusions. Both patients experienced severe neutropenia, mild asthenia, cutaneous reactions, and mild paresthesia, and recovered without incident.

Affected Organisms

Biotransformation

Hepatic. In vitro drug interaction studies revealed that docetaxel is metabolized by the CYP3A4 isoenzyme (1 major, 3 minor metabolites).

Half Life

Dose-dependent. Doses of 70 mg per square meter of body surface area (mg/m 2 ) or higher produce a triphasic elimination profile. With lower doses, assay limitations precluded detection of the terminal elimination phase. Alpha (distribution) 4 minutes. Beta 36 minutes. Gamma (terminal) 11.1 hours.

Protein Binding

About 94% protein bound, mainly to a1-acid glycoprotein, albumin, and lipoproteins.

Elimination

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.

Distribution

* 113 L

Clearance

* 21 L/h/m2 [Cancer patients after IV administration of 20–115 mg/m2]

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