Paclitaxel : It is a complex diterpin taxane obtained from bark of the Western yew tree, which exerts cytotoxic action by a novel mechanism. It enhances
TAXANES
It is a complex
diterpin taxane obtained from bark of
the Western yew tree, which exerts cytotoxic action by a novel mechanism. It
enhances polymerization of tubulin: a mechanism opposite to that of vinca
alkaloids. The microtubules are stabilized and their depolymerization is
prevented. This stability results in inhibition of normal dynamic
reorganization of the microtubule network that is essential for vital
interphase and mitotic functions. Abnormal arrays or ‘bundles’ of microtubules
are produced throughout the cell cycle. Cytotoxic action of paclitaxel
emphasizes the importance of tubulin-microtubule dynamic equilibrium.
The approved indications of paclitaxel are metastatic ovarian
and breast carcinoma after failure of first line chemotherapy and relapse
cases. It has also shown efficacy in advanced cases of head and neck cancer,
small cell lung cancer, esophageal adenocarcinoma and hormone refractory
prostate cancer.
Dose: 175 mg/m2 by i.v. infusion over 3 hr, repeated
every 3 weeks.
INTAXEL, PAXTAL 30 mg
in 5 ml cremophor emulsion (polyoxyethylated castor oil + alcohol + water) per
vial. Acute anaphylactoid reactions occur because of the cremophor
solvent. Pretreatment with dexamethasone, H1 and H2
antihistaminics is routinely used to suppress the reaction.
The major toxicity is
reversible myelosuppression and ‘stocking and glove’ neuropathy. Chest pain,
arthralgia, myalgia, mucositis and edema can be troublesome.
Docetaxel
More potent congener of
paclitaxel with the same mechanism
of action. It has been found effective in breast and ovarian cancer refractory
to first line drugs. Small cell cancer lung, pancreatic, gastric and head/neck
carcinomas are the other indications. Major toxicity is neutropenia, but
neuropathy is less frequent. Arrhythmias, fall in BP and heart failure are also
reported.
Dose: 100 mg/m2 i.v. over 1 hr; repeat at 3 weeks.
DAXOTEL 20 mg, 80 mg inj.
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