1. Clinical Overview
A fixed-dose combination of the alkylating antineoplastic agent Ifosfamide and its uroprotective antidote Mesna. Ifosfamide is a prodrug requiring hepatic activation to form cytotoxic isophosphoramide mustard, which cross-links DNA, causing cell death. Its use is limited by severe dose-limiting urotoxicity, specifically hemorrhagic cystitis, caused by its metabolite acrolein. Mesna is a sulfhydryl compound that binds to and detoxifies acrolein in the urinary tract, preventing bladder damage without interfering with the antitumor efficacy of Ifosfamide. This combination is a cornerstone of chemotherapy regimens for various solid tumors and lymphomas in India.
| Onset | Duration | Bioavailability |
|---|---|---|
| Ifosfamide: Cytotoxic effects begin with cell cycle entry (hours to days). Mesna: Uroprotection begins within 1 hour of IV administration. | Ifosfamide: Cytotoxic effects persist for several cell cycles. Mesna: Short duration; requires repeated dosing to cover the entire excretion period of Ifosfamide metabolites (typically 8-12 hours post-infusion). | Ifosfamide: Oral bioavailability is highly variable (~100% but erratic). Mesna: Oral bioavailability is approximately 50%. For this IV formulation, bioavailability is 100%. |
2. Mechanism of Action
Ifosfamide is a prodrug activated by hepatic cytochrome P450-mediated hydroxylation to 4-hydroxyifosfamide. This equilibrates with its tautomer, aldophosphamide, which spontaneously decomposes in target cells to yield the cytotoxic DNA cross-linking agent, isophosphoramide mustard, and the urotoxic metabolite, acrolein. Isophosphoramide mustard forms alkyl adducts at the N-7 position of guanine, creating interstrand and intrastrand DNA cross-links, leading to inhibition of DNA replication, transcription, and ultimately, apoptosis. Mesna provides selective uroprotection. It is administered intravenously, circulates as inactive dimesna, is filtered by the glomerulus, and is reduced back to active Mesna in the renal tubules. The free sulfhydryl group of Mesna binds specifically and rapidly to acrolein, forming a stable, non-toxic thioether compound that is excreted in urine, thereby preventing acrolein-induced damage to the bladder urothelium.
3. Indications & Uses
- Germ cell testicular cancer (salvage therapy)
- Soft tissue sarcoma
- Ewing's sarcoma
- Osteosarcoma
- Non-Hodgkin's lymphoma (relapsed/refractory)
- Cervical cancer
- Ovarian cancer
4. Dosage & Administration
Adult Dosage: Dosing is based on body surface area (BSA). Standard regimen: Ifosfamide 1.2 to 2.0 g/m²/day IV over 3-5 days, repeated every 3-4 weeks. Mesna is administered at a total daily dose equal to 60-100% of the daily Ifosfamide dose, divided and given as: 1) a bolus (20% of Ifosfamide dose) at time 0 (just before Ifosfamide), 2) a continuous infusion (40% of Ifosfamide dose) over the same period as Ifosfamide, and 3) a bolus (20% of Ifosfamide dose) 4 and 8 hours after the end of Ifosfamide infusion. For this specific 1:10 (Ifos:Mesna) fixed-dose vial, it provides a 100mg Mesna to 1000mg Ifosfamide ratio (i.e., 10% Mesna). This is typically used as PART of the Mesna regimen, often for the concurrent infusion component, with additional separate Mesna vials required for the bolus doses.
Administration: FOR INTRAVENOUS USE ONLY. Ifosfamide and Mesna are administered as slow IV infusion (typically over 30 mins to several hours, as per protocol) in 500-1000 mL of 0.9% Sodium Chloride or 5% Dextrose. MUST be given with HYPERHYDRATION (minimum 2L IV fluids/day) to ensure high urine output (>100 mL/hr) and minimize bladder contact time with metabolites. Administer in a setting with facilities for managing anaphylaxis, myelosuppression, and neurotoxicity.
5. Side Effects
Common side effects may include:
- Nausea and vomiting (severe)
- Alopecia (reversible)
- Myelosuppression (leukopenia, neutropenia, thrombocytopenia)
- Fatigue
- Anorexia
- Hematuria (microscopic, reduced with proper Mesna)
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Allopurinol | May increase risk of Ifosfamide-induced neurotoxicity; monitor closely. | Moderate |
| CYP3A4 Inducers (e.g., Phenobarbital, Phenytoin, Rifampicin, Carbamazepine) | Increase metabolism of Ifosfamide to active/toxic metabolites, potentially increasing efficacy and toxicity (myelosuppression, neurotoxicity). | Major |
| CYP3A4 Inhibitors (e.g., Ketoconazole, Itraconazole, Voriconazole, Clarithromycin) | Decrease activation of Ifosfamide, potentially reducing efficacy. | Major |
| Other Myelosuppressive Agents (e.g., other chemotherapies, radiation) | Additive bone marrow toxicity; requires dose adjustment and close CBC monitoring. | Major |
| Nephrotoxic Drugs (e.g., Aminoglycosides, Amphotericin B, NSAIDs, Cisplatin) | Increased risk of renal impairment. | Major |
| Sedatives/CNS Depressants (e.g., Benzodiazepines, Opioids) | May potentiate Ifosfamide-induced neurotoxicity (somnolence, confusion). | Moderate |
| Warfarin | Ifosfamide may alter anticoagulant response; monitor INR closely. | Moderate |
7. Patient Counselling
- DO drink at least 2-3 liters of fluids (water, juices) 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 (both men and women) after therapy.
- DO maintain good oral hygiene to reduce risk of mouth sores.
- DO NOT take any other medicines, including over-the-counter drugs, herbal supplements (especially St. John's Wort), or vitamins without consulting your oncologist.
- DO NOT receive live vaccines during treatment.
- DO NOT come into close contact with people who have infections.
8. Toxicology & Storage
Overdose: Manifestations of severe toxicity: Exaggerated myelosuppression (pancytopenia, infection, hemorrhage), severe neurotoxicity (encephalopathy, seizures, coma), severe hemorrhagic cystitis, acute renal and hepatic failure, cardiotoxicity.
Storage: Store vials/powder at controlled room temperature (15-25°C). Protect from light and moisture. Reconstituted solutions in 0.9% NaCl or 5% Dextrose are stable for up to 24 hours at 2-8°C. Do not freeze. Discard any unused portion. Keep out of reach of children. Handle with care using appropriate chemotherapy safety precautions (gloves, gown, eye protection).