Juvenile dermatomyositis
8. Cyclophosphamide
Because of its toxicity to the blood and gonads, it is a drug used only in severe disease. It is especially useful in cases of severe intestinal vasculopathy, central nervous system involvement or severe pulmonary disease.
It is administered intravenously, monthly, at doses of 500-1000 mg/m2 body surface area, for 3-6 months. A blood test should be performed 7-10 days after administration to adjust the next dose according to leukocyte and neutrophil levels, as a drop in the number of these cells is an indicator that the drug is working, but an excessive drop would be a high risk for the patient.
To reduce other associated risks, such as inflammation of the urinary bladder (haemorrhagic cystitis), preventive drugs are administered during intravenous infusion; and to reduce the risk of respiratory infection by a fungus known as Pneumocystis jirovecii, oral trimetroprin-cotrimoxazole is recommended 3 times a week.
