Cellular and clinical pharmacology of the taxanes docetaxel and paclitaxel--a review.

Paclitaxel and docetaxel are active against a range of human cancers. Their antitumor activity is based on stabilization of the microtubule dynamics and thereby disruption of the cell cycle. The taxanes are administered as intravenous solutions in a short administration schedule. Distribution of both taxanes is rapid, with large volumes of distribution and significant binding to plasma proteins. The metabolism of paclitaxel is mediated primarily by the P450 cytochrome enzymes CYP2C8 and CYP3A, whereas docetaxel is only metabolized by CYP3A4. The most common toxicities after intravenous administration are neutropenia, hypersensitivity reactions, neurotoxicity, and alopecia. Several new administration forms are in development; albumin-bound paclitaxel (Abraxane) has recently been registered. Oral formulations of taxanes have been developed, and several are now undergoing phase I trials. New formulations might improve efficacy and safety and could be easier to use.