Paclitaxel (Taxol) and docetaxel (Taxotere): not simply two of a kind.

Paclitaxel and docetaxel are the two presently clinically available representatives of the new class of taxane drugs. They share major parts of their structures and mechanisms of action, but differ in several other aspects. For instance, there is a difference in their tubulin polymer generation, and docetaxel appears twice as active in depolymerization inhibition. In vitro docetaxel also tends to be more potent in different cell lines and investigational models. While in vitro and in vivo studies suggest that prolonged exposure to paclitaxel is better than a brief exposure, no such tendency is seen for docetaxel, indicating it to be a schedule-independent drug. Clinical studies have not confirmed an advantage for prolonged exposure to paclitaxel; but do show differences in the toxicity profiles of the two drugs. These topics will be addressed in detail.