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 major dose-limiting toxicity is severe hemorrhagic cystitis. Mesna is a sulfhydryl compound that binds and detoxifies the urotoxic metabolite acrolein in the urinary tract, preventing bladder damage. This combination is a cornerstone of chemotherapy regimens for various solid tumors and sarcomas in India.
| Onset | Duration | Bioavailability |
|---|---|---|
| Ifosfamide: Cytotoxic effects begin within hours of administration as active metabolites form. Mesna: Uroprotection begins immediately upon reaching the renal tubules and bladder. | Ifosfamide: The cytotoxic effect is prolonged due to its pharmacokinetics and DNA damage. Mesna: Short duration; requires repeated dosing to maintain protective concentrations in urine during and after Ifosfamide infusion. | Ifosfamide: Oral bioavailability is highly variable and unreliable (~100% but not recommended orally). Administered IV. Mesna: Oral bioavailability is approximately 50-75%; IV bioavailability is 100%. |
2. Mechanism of Action
Ifosfamide is a prodrug activated in the liver by cytochrome P450-mediated hydroxylation to 4-hydroxyifosfamide. This equilibrates with its tautomer, aldophosphamide, which spontaneously decomposes in target cells to phosphoramide mustard and acrolein. Phosphoramide mustard is the ultimate cytotoxic agent that forms irreversible interstrand and intrastrand cross-links with DNA 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, remains in an inactive disulfide form (dimesna) in circulation. In the renal tubules, dimesna is reduced back to free Mesna, which binds directly and detoxifies acrolein by forming a stable, non-toxic thioether conjugate. It also binds to and inactivates other 4-hydroxy metabolites of Ifosfamide locally in the bladder, preventing direct contact with the urothelium.
3. Indications & Uses
- Germ cell testicular cancer (salvage therapy)
- Soft tissue sarcoma (e.g., Ewing's sarcoma, rhabdomyosarcoma)
- Osteosarcoma
- Non-Hodgkin's lymphoma (relapsed/refractory)
- Cervical cancer
- Ovarian cancer
4. Dosage & Administration
Adult Dosage: Ifosfamide: 1.2 to 2.0 g/m²/day IV infusion over 30 min to 2 hours for 3 to 5 consecutive days, repeated every 3-4 weeks. Mesna: Given at 20% (w/w) of the Ifosfamide dose per administration. Standard IV regimen: Mesna (200mg in this combo is part of the dose) is given as a bolus IV at 20% of Ifosfamide dose at time 0, then continuous IV infusion at 40% of Ifosfamide dose over 12-24 hours, OR repeated IV bolus doses at 4 and 8 hours after Ifosfamide. Total daily Mesna dose equals 60-120% of the daily Ifosfamide dose.
Administration: 1. Administer in a hospital setting with resuscitation facilities. 2. Pre-hydrate with 1-2 L of IV fluids (e.g., Normal Saline) before chemotherapy. 3. Administer antiemetic prophylaxis. 4. Reconstitute/vial contents as per manufacturer. Ifosfamide is infused first, followed immediately by the scheduled Mesna doses. 5. Maintain high urine output (>100 mL/hr) during and for at least 24-48 hours post-infusion. 6. Monitor urine for blood (hematuria) regularly. 7. The fixed-dose combination vial (200mg Mesna + 1g Ifosfamide) is one component; additional standalone Mesna vials are ALWAYS required to complete the full uroprotective regimen.
5. Side Effects
Common side effects may include:
- Nausea and vomiting (severe)
- Alopecia (reversible)
- Myelosuppression (leukopenia, neutropenia, thrombocytopenia, anemia)
- Fatigue/asthenia
- Anorexia
- Hemorrhagic cystitis (prevented/ mitigated by Mesna)
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Allopurinol | May increase risk of Ifosfamide-induced neurotoxicity | Moderate |
| CYP3A4 Inducers (e.g., Phenobarbital, Phenytoin, Rifampicin, Carbamazepine, St. John's Wort) | Increased metabolism of Ifosfamide to active/toxic metabolites, potentially increasing efficacy and toxicity (myelosuppression, neurotoxicity) | Major |
| CYP3A4 Inhibitors (e.g., Ketoconazole, Itraconazole, Voriconazole, Clarithromycin, Ritonavir) | Decreased activation of Ifosfamide, potentially reducing efficacy | Major |
| Warfarin | Ifosfamide may potentiate anticoagulant effect, increasing INR and bleeding risk | Moderate |
| Cisplatin | Increased risk of nephrotoxicity, ototoxicity, and neurotoxicity. Sequential administration (Ifosfamide before Cisplatin) may reduce toxicity. | Major |
| Other Myelosuppressive agents (e.g., Doxorubicin, Etoposide) | Additive bone marrow suppression | Major |
| Succinylcholine | Ifosfamide may inhibit plasma cholinesterase, prolonging apnea | Moderate |
| Live Vaccines (e.g., MMR, Varicella, Yellow Fever) | Risk of disseminated infection due to immunosuppression | Major |
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.
- DO report immediately any blood in urine, pain on urination, or inability to urinate.
- DO use effective contraception (both males and females) during and for at least 6 months after therapy.
- DO maintain good oral hygiene to reduce risk of mouth sores.
- DO inform all your doctors and dentists you are on chemotherapy.
- DONT take any other medicines, including OTC, herbal (e.g., St. John's Wort), or supplements without consulting your oncologist.
- DONT miss scheduled blood tests (CBC, renal, liver function).
- DONT come in contact with people who have infections (colds, flu).
- DONT get pregnant or breastfeed.
8. Toxicology & Storage
Overdose: Manifestations of severe toxicity: Profound myelosuppression (pancytopenia, sepsis), severe hemorrhagic cystitis with potential bladder necrosis, severe encephalopathy (coma, seizures), acute renal failure, cardiotoxicity, and death.
Storage: Store vials/powder at controlled room temperature (15-25°C). Protect from light and moisture. Reconstituted solutions: Ifosfamide is stable for varying periods depending on diluent (e.g., 7 days at 5°C in Water for Injection). Mesna solutions are stable for 24 hours at room temperature. Always refer to the specific manufacturer's package insert. Do not freeze. Keep out of reach of children. Dispose of unused chemotherapy waste as per hospital biohazard protocols.