Cytarabine
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Image:Cytarabine.png | |
| 1β-arabinofuranosylcytosine | |
| CAS number 147-94-4 | ATC code L01BC01 |
| Chemical formula | C9H13N3O5 |
| Molecular weight | 243.21 |
| Bioavailability | Orally, less than 20% of a dose of cytarabine is absorbed from the gastrointestinal tract and is ineffective by this route. Subcutaneously or intramuscularly, tritium labelled cytarabine produces peak plasma concentrations of radioactivity within 20 to 60 minutes which are considerably lower than those attained after intravenous administration. Continuous intravenous infusions produce relatively constant plasma levels in 8 to 24 hours. |
| Metabolism | Liver |
| Elimination half-life | Intravenous doses of cytarabine exhibit a biphasic elimination, with an initial distribution half-life of about ten minutes during which time a major portion of the drug is metabolised in the liver to the inactive metabolite uracil arabinoside. The secondary elimination half-life is longer, approximately one to three hours. Metabolism also occurs in the kidneys, gastrointestinal mucosa, granulocytes and other tissues. |
| Excretion | Cytarabine is mainly excreted via the kidney with 70 to 80% of a dose administered by any route appearing in the urine within 24 hours; approximately 90% as the metabolite and 10% as unchanged drug |
| Pregnancy category | D (USA) D (Aus) |
| Legal status | ? |
| Routes of administration | Injectable (intravenous injection or infusion, or subcutaneously) |
Cytarabine is a shortened form of cytosine arabinoside, a commonly used chemotherapy agent used mainly in the treatment of leukemia and non-Hodgkin lymphoma. It is also known as Ara-C, Cytosar®-U, Tarabine® PFS or other local brand names.
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History
Cytarabine was discovered in Europe in the 1960s. It gained FDA approval in June 1969 and was initially marketed in the US by Upjohn as Cytosar-U.
Mechanism
Cytosine arabinoside is an antimetabolic agent with the chemical name of 1β-arabinofuranosylcytosine. Its mode of action is due to its rapid conversion into cytosine arabinoside triphosphosphate, which damages DNA when the cell cycle holds in the S phase (synthesis of DNA). Rapidly dividing cells, which require DNA replication for mitosis, are therefore most affected. Cytosine arabinoside also inhibits both DNA and RNA polymerases and nucleotide reductase enzyme needed for the DNA synthesis. Cytarabine is rapidly deaminated in the body into the inactive uracil derivative form and therefore, it is often given by continuous intravenous infusion.
Clinical uses
Cytarabine is mainly used in the treatement of acute myelogenous leukemia where it is the backbone of induction chemotherapy. Cytarabine possessess also an antiviral activity, and it has been used for the treatment of generalised herpes infection. However, cytarabine is not very selective and causes bone marrow suppression and other severe side effects, so it is used mainly for the chemotherapy of cancer.
One of the unique toxicities of cytarabine is cerebellar toxicity when given in high doses.
Cytarabine is also used in the study of the nervous system to control the proliferation of glial cells in cultures, the amount of glial cells having an important impact on neurons.
External links
- MedlinePlus page on cytarabine
- ADAP drugs page on cytarabine
- BC Cancer network page on cytarabine
- Chembank entry
References
- Hobbs J.B. in Comprehensive Medicinal Chemistry Vol. 2: (ed. Sammes, Peter G.) Pergamon Press, 1990
- Männistö P.T., Tuominen R.K. in Farmakologia ja Toksikologia, 5th edition: (ed. Koulu, Tuomisto, Paasonen) Medicina, 1996
- Rang H.P., Dale M.M., Ritter J.M.: Pharmacology, 3rd edition. Pearson Professional Ltd, 1995.