1. Clinical Overview
A fixed-dose combination of the alkylating antineoplastic agent Ifosfamide and its uroprotective antidote Mesna. Ifosfamide is an oxazaphosphorine nitrogen mustard prodrug used primarily in combination chemotherapy regimens for various solid tumors and lymphomas. Mesna is a sulfhydryl compound that binds to and detoxifies the urotoxic metabolite acrolein, preventing hemorrhagic cystitis, a dose-limiting toxicity of Ifosfamide. This combination is a cornerstone of treatment for germ cell tumors, soft tissue sarcomas, and certain lymphomas in the Indian oncology setting.
| Onset | Duration | Bioavailability |
|---|---|---|
| Ifosfamide: Metabolic activation required; cytotoxic effects begin within hours of administration. Mesna: Rapid, within 1-2 hours of IV administration for uroprotection. | Ifosfamide: Cytotoxic effects are prolonged due to its alkylating mechanism, affecting cells throughout the cell cycle. Mesna: Short-lived; requires repeated dosing to maintain protective thiol concentration in urine (protection lasts ~4 hours per dose). | Ifosfamide: Oral bioavailability is highly variable and unreliable (~96% but with erratic absorption); exclusively administered intravenously in clinical practice. Mesna: Oral bioavailability is approximately 50-75%; IV bioavailability is 100%. |
2. Mechanism of Action
Ifosfamide is a prodrug activated by hepatic cytochrome P450-mediated hydroxylation to 4-hydroxyifosfamide. This active form circulates and enters cells, where it undergoes spontaneous decomposition to isophosphoramide mustard and acrolein. Isophosphoramide mustard is the ultimate cytotoxic agent that forms irreversible cross-links between DNA strands (specifically at the N-7 position of guanine), disrupting DNA replication and transcription, leading to apoptosis. Acrolein is a highly reactive urotoxic metabolite. Mesna provides selective uroprotection. It is a thiol compound that, when delivered to the kidneys, is reduced to its active form. It binds directly and detoxifies acrolein in the urinary bladder, forming a stable, non-toxic thioether compound, thereby preventing hemorrhagic cystitis.
3. Indications & Uses
- Germ Cell Tumors (Testicular, Ovarian)
- Soft Tissue Sarcomas (e.g., Ewing's sarcoma, Rhabdomyosarcoma)
- Non-Hodgkin's Lymphoma (Relapsed/Refractory)
- Hodgkin's Lymphoma (Salvage therapy)
- Small Cell Lung Cancer (as part of combination regimens)
4. Dosage & Administration
Adult Dosage: Standard dose: Ifosfamide 1.2 to 2.0 g/m²/day IV for 3-5 consecutive days, repeated every 3-4 weeks. Mesna dose is 20% of the Ifosfamide dose (by weight) administered at 0, 4, and 8 hours after the start of Ifosfamide infusion. For this fixed 1g/200mg vial: Often used as a single daily dose component, with additional separate Mesna doses required at 4 and 8 hours.
Administration: For IV use only. Ifosfamide is reconstituted and diluted in 500-1000 mL of 0.9% Sodium Chloride or 5% Dextrose. Infuse over a minimum of 30 minutes to several hours (as per protocol). HYDRATION: Aggressive pre- and post-hydration with at least 2-3 L of fluids/day is mandatory to dilute urinary metabolites. Mesna (from this vial and subsequent doses) is administered as IV bolus or short infusion. NEVER mix Ifosfamide and Mesna in the same infusion bag/syringe.
5. Side Effects
Common side effects may include:
- Nausea and Vomiting (highly emetogenic)
- Alopecia (reversible)
- Myelosuppression (Leukopenia, Neutropenia, Thrombocytopenia)
- Fatigue
- Anorexia
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Allopurinol | May potentiate Ifosfamide myelotoxicity; monitor blood counts closely. | Moderate |
| CYP3A4 Inducers (e.g., Phenobarbital, Rifampicin, Carbamazepine) | Increase metabolism of Ifosfamide to active/toxic metabolites, potentially increasing efficacy and toxicity (neuro, uro). | Major |
| CYP3A4 Inhibitors (e.g., Ketoconazole, Itraconazole, Clarithromycin) | Decrease activation of Ifosfamide, potentially reducing efficacy. | Major |
| Other Myelosuppressive Agents/Chemotherapy | Additive bone marrow suppression. Requires careful sequencing and monitoring. | Major |
| Nephrotoxic Drugs (e.g., Aminoglycosides, Amphotericin B, NSAIDs) | Increased risk of renal dysfunction, altering Ifosfamide/Mesna excretion. | Major |
| Warfarin | Ifosfamide may potentiate anticoagulant effect; monitor INR. | Moderate |
| Sedatives (e.g., Benzodiazepines, Phenothiazines) | May exacerbate Ifosfamide-induced CNS depression. | Moderate |
7. Patient Counselling
- DO drink at least 2-3 liters of fluids daily for 2-3 days after each treatment to flush your bladder.
- DO empty your bladder frequently, including during the night after treatment.
- DO report immediately any blood in urine, pain on urination, or inability to urinate.
- DO use effective contraception during and for at least 6 months (men) and 1 year (women) after therapy.
- DONT take any other medicines, including OTC drugs or herbal supplements, without consulting your oncologist.
- DONT miss follow-up appointments for blood tests (CBC, renal function).
8. Toxicology & Storage
Overdose: Manifestations of severe toxicity: Exaggerated myelosuppression (pancytopenia, infection, hemorrhage), severe neurotoxicity (coma, seizures), severe hemorrhagic cystitis, acute renal and hepatic failure, cardiotoxicity.
Storage: Store vials in a refrigerator (2°C to 8°C). Protect from light. Reconstituted solutions: Ifosfamide is stable for 24 hours at room temperature (25°C) or 7 days under refrigeration (2-8°C) when diluted in 0.9% NaCl or 5% Dextrose. Mesna solution is stable for 24 hours at room temperature. Do not freeze. Discard any unused portion. Keep out of reach of children.