On March 21, 2002, the FDA approved mesna tablets (Mesnex®, a trademark of Baxter Healthcare S.A.) as a prophylactic agent to reduce the incidence of ifosfamide-induced hemorrhagic cystitis. Ifosfamide is chemotherapy that is given as a treatment for some types of cancer. After ifosfamide and the first dose of mesna are administered intravenously, subsequent doses of mesna may be given intravenously or orally.

Clinical studies comparing the recommended IV-IV-IV and the IV-oral-oral mesna regimens demonstrated < 5 percent incidence of grade 3 – 4 hematuria in both arms when used in conjunction with ifosfamide 1.2-2.0 gm/m2 for 3-5 days.

In a meta-analysis of four controlled studies, the safety profile of the IV-oral-oral regimen (N=119) was similar to the all IV regimen (N=119). Nausea and vomiting were the most common adverse events. Because mesna is used in combination with ifosfamide, it is difficult to distinguish the adverse reactions which may be due to mesna from those caused by the concomitantly administered cytotoxic agent. The most frequently reported adverse reactions from single dose Phase I studies of IV mesna alone were headache, injection site reactions, flushing, dizziness, nausea, vomiting, somnolence, diarrhea, anorexia, fever, pharyngitis, hyperaesthesia, influenza-like symptoms and coughing.

Mesna does not prevent hemorrhagic cystitis in all patients and does not decrease the incidence of other chemotherapy-related adverse events.

Dosage and administration: The recommended IV and oral mesna regimens differ in the ratio of mesna:ifosfamide and times of administration after ifosfamide. The recommended dosing schedules are as follows:

IV-IV-IV: Mesna is given as an IV bolus injection in a dosage equal to 20 percent of the ifosfamide dosage at the time of ifosfamide administration and 4 and 8 hours after each dose of ifosfamide. The total daily dose of mesna is 60 percent of the ifosfamide dose.

IV-oral-oral: Mesna is given as an IV bolus injection in a dosage equal to 20 percent of the ifosfamide dosage at the time of ifosfamide administration. Mesna tablets are given orally in a dosage equal to 40 percent of the ifosfamide dose at 2 and 6 hours after each dose of ifosfamide. The total daily dose of mesna is 100 percent of the ifosfamide dose.

Patients who vomit within two hours of taking oral mesna should repeat the dose or receive IV mesna. The efficacy and safety of this ratio of IV-oral-oral mesna has not been established as being effective for daily doses of ifosfamide higher than 2.0 gm/m2 for 3-5 days.

Full prescribing information is available, including clinical trial information, safety, dosing, drug-drug interactions and contraindications.

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