1. Clinical Overview
Ifosfamide is a nitrogen mustard alkylating agent and an oxazaphosphorine analog of cyclophosphamide. It is a prodrug requiring hepatic activation via cytochrome P450 (CYP) enzymes, primarily CYP3A4 and CYP2B6, to form active alkylating metabolites, primarily isophosphoramide mustard. It cross-links DNA strands, inhibiting DNA synthesis and function, leading to cell death. It is a cornerstone of combination chemotherapy regimens for various solid tumors and lymphomas in India.
| Onset | Duration | Bioavailability |
|---|---|---|
| Activation begins within 1-2 hours of IV administration. | Cytotoxic effects persist for the duration of the cell cycle exposure; pharmacodynamic effects last beyond measurable plasma levels due to DNA adduct formation. | Not applicable; administered exclusively via intravenous infusion. |
2. Mechanism of Action
Ifosfamide is a prodrug activated in the liver by mixed-function oxidase enzymes. The active metabolites, primarily isophosphoramide mustard, form highly reactive aziridinium ions. These ions alkylate nucleophilic sites on DNA, preferentially at the N-7 position of guanine, leading to intra-strand and inter-strand DNA cross-links. This disrupts DNA replication and transcription, ultimately triggering apoptosis (programmed cell death) in rapidly dividing cells.
3. Indications & Uses
- Germ cell testicular cancer (as part of salvage therapy, e.g., VIP regimen)
- Soft tissue sarcoma (e.g., in combination with Doxorubicin)
- Ewing's sarcoma
- Non-Hodgkin's lymphoma (particularly relapsed/refractory)
- Hodgkin's lymphoma (salvage therapy)
4. Dosage & Administration
Adult Dosage: 1.2 to 2.5 g/m² body surface area per day, administered intravenously over 30 minutes to several hours for 3 to 5 consecutive days. Total dose per cycle typically ranges from 5 to 10 g/m². Dose is ALWAYS part of a specific, protocol-defined combination chemotherapy regimen.
Administration: For 1gm vial: Reconstitute with 20-50 mL of Water for Injection or Bacteriostatic Water for Injection. Further dilute in 500-1000 mL of compatible IV fluid (e.g., 0.9% Sodium Chloride Injection, 5% Dextrose Injection) to a final concentration typically between 0.6 to 20 mg/mL. Administer as a slow IV infusion over 30 minutes to several hours. MESNA MUST BE ADMINISTERED CONCURRENTLY. Ensure vigorous hydration (minimum 2 L/day) before, during, and after infusion to dilute urinary metabolites.
5. Side Effects
Common side effects may include:
- Nausea and vomiting (can be severe)
- Alopecia (hair loss)
- Myelosuppression: Leukopenia, Neutropenia (nadir 7-14 days), Thrombocytopenia (nadir 10-15 days), Anemia
- Hemorrhagic cystitis (preventable with Mesna & hydration)
- Fatigue
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Allopurinol | May increase risk of myelosuppression. | Moderate |
| Warfarin | Ifosfamide may enhance anticoagulant effect, increasing INR and bleeding risk. | Major |
| Phenobarbital, Phenytoin, Carbamazepine | Induce CYP enzymes, potentially increasing activation of ifosfamide to toxic metabolites, increasing risk of neurotoxicity and other adverse effects. | Major |
| Cimetidine | Inhibits CYP enzymes, may decrease activation of ifosfamide, potentially reducing efficacy. | Moderate |
| Cisplatin | Additive nephrotoxicity and ototoxicity. May also reduce ifosfamide metabolism, increasing toxicity. | Major |
| Doxorubicin | Additive cardiotoxicity. Monitor cardiac function. | Major |
| Live vaccines | Risk of disseminated infection due to immunosuppression. Contraindicated. | Major |
7. Patient Counselling
- DO drink at least 2-3 liters of fluids daily for 2-3 days after each dose, as advised, to flush your bladder.
- DO report immediately any blood in urine, painful urination, or decreased urine output.
- DO report any signs of infection (fever, chills, sore throat) or unusual bleeding/bruising.
- DO use effective contraception during and for at least 6 months (men) and 1 year (women) after therapy.
- DO inform all healthcare providers (including dentists) that you are on chemotherapy.
- DONT take any other medicines, including over-the-counter drugs, herbal supplements (especially St. John's Wort), or vitamins without consulting your oncologist.
- DONT miss scheduled blood tests to monitor your blood counts and kidney function.
- DONT consume alcohol during treatment.
8. Toxicology & Storage
Overdose: Manifestations of overdose would be severe exacerbations of known toxicities: Profound myelosuppression (pancytopenia, infection, hemorrhage), severe hemorrhagic cystitis, acute renal failure, severe encephalopathy (ranging from confusion to coma and seizures), and cardiotoxicity.
Storage: Store unopened vials at controlled room temperature (15°-25°C). Protect from light. Reconstituted solution (in Water for Injection) is stable for 7 days at 5°C (refrigerated) or 3 days at 25°C. Further diluted solutions in infusion bags (NS or D5W) should be used immediately or stored refrigerated and used within 24 hours. Do not freeze. Discard any unused portion. Follow aseptic technique.