It is also used less commonly to treat some noncancer diseases. There is no published research linking antioxidant vitamins to reduced cyclophosphamide effectiveness in cancer treatment. In a study of mice with vitamin A deficiency, vitamin A supplementation enhanced the anticancer action of cyclophosphamide. Another animal research report indicated that vitamin C may increase the effectiveness of cyclophosphamide without producing new side effects. It is too early to know if adding antioxidants to cyclophosphamide for cancer treatment is better than cyclophosphamide alone.
Vitamin A can be toxic in high amounts.
Intravenous injections of the antioxidant, glutathione , may protect the bladder from damage caused by cyclophosphamide. Preliminary evidence suggests, but cannot confirm, a protective action of glutathione in the bladders of people on cyclophosphamide therapy. There is no evidence that glutathione taken by mouth has the same benefits. It is recommended to take cyclophosphamide on an empty stomach. 5 People with questions should ask their prescribing doctor or pharmacist.