Drug Groups

approved

Description

A cyclodecane isolated from the bark of the Pacific yew tree, TAXUS brevifolia. It stabilizes microtubules in their polymerized form leading to cell death. [PubChem] ABI-007 (Abraxane) is the latest attempt to improve upon paclitaxel, one of the leading chemotherapy treatments. Both drugs contain the same active agent, but Abraxane is delivered by a nanoparticle technology that binds to albumin, a natural protein, rather than the toxic solvent known as Cremophor. It is thought that delivering paclitaxel with this technology will cause fewer hypersensitivity reactions and possibly lead to greater drug uptake in tumors.

Indication

Used in the treatment of Kaposi's sarcoma and cancer of the lung, ovarian, and breast.

Pharmacology

Paclitaxel is a taxoid antineoplastic agent indicated as first-line and subsequent therapy for the treatment of advanced carcinoma of the ovary, and other various cancers including breast cancer. Paclitaxel is a novel antimicrotubule agent that 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, paclitaxel induces abnormal arrays or "bundles" of microtubules throughout the cell cycle and multiple asters of microtubules during mitosis.

Toxicity

Rat (ipr) LD₅₀=32530 µg/kg. Symptoms of overdose include bone marrow suppression, peripheral neurotoxicity, and mucositis. Overdoses in pediatric patients may be associated with acute ethanol toxicity.

Affected Organisms

Biotransformation

Hepatic. In vitro studies with human liver microsomes and tissue slices showed that paclitaxel was metabolized primarily to 6a-hydrox-ypaclitaxel by the cytochrome P450 isozyme CYP2C8; and to two minor metabolites, 3’-p-hydroxypaclitaxel and 6a, 3’-p-dihydroxypaclitaxel, by CYP3A4.

Absorption

I.V injected

Half Life

Average distribution half-life of 0.34 hours and an average elimination half-life of 5.8 hours.

Protein Binding

89%-98%

Elimination

In 5 patients administered a 225 or 250 mg/m2 dose of radiolabeled paclitaxel as a 3-hour infusion, a mean of 71% of the radioactivity was excreted in the feces in 120 hours, and 14% was recovered in the urine.

Distribution

* 227 to 688 L/m2

Clearance

* 21.7 L/h/m2 [Dose 135 mg/m2, infusion duration 24 h]
* 23.8 L/h/m2 [Dose 175 mg/m2, infusion duration 24 h]
* 7 L/h/m2 [Dose 135 mg/m2, infusion duration 3 h]
* 12.2 L/h/m2 [Dose 175 mg/m2, infusion duration 3 h]

References

External Links