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Ifosfamide


ACCESSION NB: DB01181 (APRD00007)


TYPE: small molecule


GROUP: approved


DESCRIPTION:
Positional isomer of cyclophosphamide which is active as an alkylating agent and an immunosuppressive agent. [PubChem]

VOLUME OF DISTRIBUTION: Not Available

CATEGORIES:
Antineoplastic Agents Immunosuppressive Agents Antineoplastic Agents, Alkylating

ABSORPTION: Not Available

INDICATION:
Used as a component of various chemotherapeutic regimens as third-line therapy for recurrent or refractory germ cell testicular cancer. Also used as a component of various chemotherapeutic regimens for the treatment of cervical cancer, as well as in conjunction with surgery and/or radiation therapy in the treatment of various soft tissue sarcomas. Other indications include treatment of osteosarcoma, bladder cancer, ovarian cancer. small cell lung cancer, and non-Hodgkin's lymphoma.

PHARMACODYNAMICS:
Ifosfamide requires activation by microsomal liver enzymes to active metabolites in order to exert its cytotoxic effects. Activation occurs by hydroxylation at the ring carbon atom 4 to form the unstable intermediate 4-hydroxyifosfamide. This metabolite than rapidly degrades to the stable urinary metabolite 4-ketoifosfamide. The stable urinary metabolite, 4-carboxyifosfamide, is formed upon opening of the ring. These urinary metabolites have not been found to be cytotoxic. N, N-bis (2-chloroethyl)-phosphoric acid diamide (ifosphoramide) and acrolein are also found. The major urinary metabolites, dechloroethyl ifosfamide and dechloroethyl cyclophosphamide, are formed upon enzymatic oxidation of the chloroethyl side chains and subsequent dealkylation. It is the alkylated metabolites of ifosfamide that have been shown to interact with DNA. Ifosfamide is cycle-phase nonspecific.

MECHANISM OF ACTION:
The exact mechanism of ifosfamide has not been determined, but appears to be similar to other alkylating agents. Ifosfamide requires biotransformation in the liver by mixed-function oxidases (cytochrome P450 system) before it becomes active. After metabolic activation, active metabolites of ifosfamide alkylate or bind with many intracellular molecular structures, including nucleic acids. The cytotoxic action is primarily through the alkylation of DNA, done by attaching the N-7 position of guanine to its reactive electrophilic groups. The formation of inter and intra strand cross-links in the DNA results in cell death.

PROTEIN BINDING:
Minimal

METABOLISM:
Primarily hepatic Enzyme Metabolite Reaction Km Vmax Prostaglandin G/H synthase 1 4-Hydroxyifosfamide 4-hydroxylation Cytochrome P450 3A5 3-Dechloroethylifosfamide Cytochrome P450 3A5 2-Dechloroethylifosfamide Cytochrome P450 3A5 Chloroacetaldehyde Cytochrome P450 3A4 3-Dechloroethylifosfamide Cytochrome P450 3A4 2-Dechloroethylifosfamide Cytochrome P450 3A4 Chloroacetaldehyde Cytochrome P450 3A4 4-hydroxyifosfamide 4-hydroxylation 800 139.5 Cytochrome P450 2B6 3-Dechloroethylifosfamide Cytochrome P450 2B6 2-Dechloroethylifosfamide Cytochrome P450 2B6 Chloroacetaldehyde Cytochrome P450 2B6 4-hydroxyifosfamide 4-hydroxylation 0 0

TOXICITY:
LD50 (mouse) = 390-1005 mg/kg, LD50 (rat) = 150-190 mg/kg. Side effects include nausea, vomiting and myelosuppression. Toxic effects include central nervous system toxicity (confusion, hallucinations) and urotoxic effects (cystitis, blood in urine).

AFECTED ORGANISMS:
Humans and other mammals