MesnaRx

Trade Names: Mesnex

Drug Class: Thiol compound

Preparations: Injection, 100 mg/mL (10 mL); tablet, 400 mg

Dose
Intravenous: Administer mesna to a total of 60% of the cyclophosphamide dose (milligram for milligram) divided into several doses, given 15 minutes before cyclophosphamide and 4 and 8 hours after cyclophosphamide.
Oral: Administer mesna equivalent to 40% of the cyclophosphamide dose (milligram for milligram) 2 hours before cyclophosphamide and two additional doses at 3- to 4-hour intervals after cyclophosphamide (total dose, 120% of cyclophosphamide dose). Intravenous mesna is recommended if patient vomits.

Indications: Prophylaxis of hemorrhagic cystitis caused by cyclophosphamide or ifosfamide

Mechanism of Action: Binds and detoxifies with urotoxic metabolites such as acrolein (seen with cyclophosphamide therapy)

Contraindications: Hypersensitivity to mesna

Pregnancy Risk: B

Adverse Effects
Common: Bad taste, headache, diarrhea, nausea, musculoskeletal pain
Uncommon: Allergic rash, hives

Comments: Most rheumatologists prefer intravenous protocols to oral cyclophosphamide because there is less hemorrhagic cystitis. Some rheumatologists use mesna regularly. Others, because the doses of cyclophosphamide used in rheumatology are relatively low compared to those used in oncology, reserve it for patients experiencing hemorrhagic cystitis with intravenous or oral cyclophosphamide therapy. There is little evidence-based data to inform decisions about mesna in rheumatology. Mesna tablets are expensive compared to an equivalent dose of the IV preparation. Thus, the IV  preparation has been used  orally, but because it  has an unpleasant smell and taste it has been mixed with a carbonated drink or  juice.

Clinical Pharmacology: Peak plasma levels 2–3 hours after oral administration; rapidly oxidized in the blood to mesna disulfide; excreted by glomerular filtration. Half-life of mesna disulfide is 1.2 hours.

Cost: $$$

BIBLIOGRAPHY

Monach PA, Arnold LM, Merkel PA. Incidence and prevention of bladder toxicity from cyclophosphamide in the treatment of rheumatic diseases: a data-driven review. Arthritis Rheum 2010;62:9-21. PMID: 20039416.