Xitabin
Generic Name :Capecitabine
Indications
Xitabin is a nucleoside metabolic inhibitor with antineoplastic activity indicated for:
- Adjuvant Colon Cancer: Patients with Dukes’C colon cancer.
- Metastatic Colorectal Cancer: First-line as monotherapy when treatment with fluoropyrimidine therapy alone is preferred.
- Metastatic Breast Cancer: In combination with docetaxel after failure of prior anthracycline containing therapy.
- As monotherapy in patients resistant to both paclitaxel and an anthracycline-containing regimen.
Pharmacology
Capecitabine is a preparation of Capecitabine, an orally-administered chemotherapeutic agent used in the treatment of cancers. Capecitabine is a prodrug, that is enzymatically converted to fluorouracil (antimetabolite) in the tumour, where it inhibits DNA synthesis and slows growth of tumour tissue.
Capecitabine is a prodrug that is selectively tumour-activated to its cytotoxic moiety, fluorouracil, by thymidine phosphorylase, an enzyme found in higher concentrations in many tumours compared to normal tissues or plasma. Fluorouracil is further metabolized to two active metabolites, 5-fluoro-2′-deoxyuridine 5-monophosphate (FdUMP) and 5-fluorouridine triphosphate (FUTP), within normal and tumour cells. These metabolites cause cell injury by two different mechanisms. First, FdUMP and the folate cofactor, N5-10 methylenetetrahydrofolate, bind to thymidylate synthase (TS) to form a covalently bound ternary complex. This binding inhibits the formation of thymidylate from 2-deoxyuridylate. Thymidylate is the necessary precursor of thymidine triphosphate, which is essential for the synthesis of DNA, therefore a deficiency of this compound can inhibit cell division. Secondly, nuclear transcriptional enzymes can mistakenly incorporate FUTP in place of uridine triphosphate (UTP) during the synthesis of RNA. This metabolic error can interfere with RNA processing and protein synthesis through the production of fraudulent RNA.
Dosage & Administration
Monotherapy: 1250 mg/m2 twice daily orally for 2 weeks followed by a one-week rest period in 3-week cycles
Adjuvant treatment: Is recommended for a total of 6 months (8 cycles)
In combination with docetaxel: The recommended dose of Capecitabine is 1250 mg/m2 twice daily for 2 weeks followed by a 7-day rest period, combined with docetaxel at 75 mg/m2 as a 1-hour IV infusion every 3 weeks. Capecitabine dosage may need to be individualized to optimize patient management. Capecitabine dosage has to be reduced by 25% in patients with moderate renal impairment.
Example: A person whose body weight is 64 kg and height is 1.64 m has a body surface area of 1.7 m2 and should take 4 tablets of 500 mg and 1 tablet of 150 mg two times daily.
The tablets should be taken in morning and evening as prescribed by doctor. The tablets should be taken within 30 minutes after the end of a meal (breakfast and dinner) and swallowed whole with water. Tablets should not be cut or crushed. Capecitabine should only be prescribed by a doctor experienced in the use of anticancer medicines.
