Paclitaxel - one of the most widely used chemotherapy agents

Paclitaxel is an anti-cancer drug, also known as Taxol and Onxol. The drug is first line treatment for ovarian, breast, lung, and colon cancer and second line treatment for AIDS-related Kaposi’s sarcoma. It is so effective that some oncologists refer to the period before 1994 as the “pre-Taxol” era for treating breast cancer.

Paclitaxel is classified as an antimicrotubule agent; it stops the growth of the tumor by inhibiting cell division. During mitosis, the cell uses structures called micotubules to move around the chromosomes. This class of chemotherapy drug works by thowing a wrench into the M-Phase of the cell cycle.

Although there are patents for oral administration of Taxol, it is typically administered intravenously. It is supplied as a clear, viscous, non-aqueous concentrate, in 30mg/5 ml to 30mg/50ml multi dose vials. The diluted solution is stable at ambient temperatures and room lighting conditions for 24 hours. Normal IV tubing and filters can be used. The drug goes throughout the body ("systematic") and gets in all tissues and fluids, which can lead to negative side effects. For some cancers, oncologists put the Taxol in a bodily cavity to concentrate its effect in one part of the body.

A common regimen would be 175 mg / m2 delivered over 3 hours every 3 weeks for 4 cycles in combination with other chemotherapy. Severe hypersensitivity reactions occur in 2-4% of the patients in clinical trials. Fatal reactions have occurred despite premedication.

Taxol is also one of the most recognizable, celebrated, and controversial products in recent years. Taxol has been called a miracle drug. Since it has been used in the treatment of breast cancer, the survival rate has doubled. Taxol has received the ire of conservationists, holds records for sales volume, and has been the subject of public debate and congressional hearings. Its discovery and development as a drug is a fascinating path of chance, intuition, expensive risk taking, perseverance, and success.

After a study of medicinal herbs and folkloric knowledge, extracts from juniper trees were found to have some anti-cancer properties. This led to a search for more active conifers. In 1962, a botanist working for the USDA in Washington State was sampling trees with “cancer plant” potential. The 1645th plant sample collected was a Pacific Yew tree. This tree is a very slow growing hardwood that grows in the shadows of giant conifers and has long been considered a “trash tree”. The tree has very few pests because almost every part of the tree is poisonous. Historically, the wood from the Yew tree has been good for making bows as well as poison arrows; it is associated with death. The Latin name Taxus brevifolia is related to the word “toxin”.

In addition to the brand name Taxol, Paclitaxel is sold in Canada under the names Abraxane® and Apo-Paclitaxel®. In Mexico it goes by the names Aclixel, Asotax, Bristaxol, Cryoxet, and Praxel

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From the forest comes a medicine...
paclitaxel molecule
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Information on this anti-cancer drug — © 2009 to 2014.