Cyclophosphamide (Cytoxan®)

Cytoxan, also known as cyclophosphamide (sye-kloe-FOSS-fa-mide) is a powerful medication that suppresses the immune system and is used primarily to treat more serious kinds of inflammation in a wide variety of illnesses. Conditions include more severe complications of lupus such as kidney, nervous system or blood disease; serious blood vessel inflammation (vasculitis) that may threaten kidney, lung, brain or other organs; and, less commonly, severe complications of rheumatoid arthritis.

Cytoxan may be given by mouth or by intravenous injection. If oral treatment is prescribed, the medication is given on a daily basis, usually one dose each morning. The dose is based on body weight and ranges between 1 mg to 2 mg per kilogram of body weight. One kg is about 2.2 pounds. The dose is adjusted according to the response of the inflammation and the response of the white blood cell count to the medication. Usually this translates into 75 mg to 200 mg each day.

In some instances, particularly lupus kidney disease, this medication may be given as an intravenous injection. This usually is given once a month for up to six months and then variably thereafter. The dose ranges between 0.5 g to 1.0 g (500 mg to1,000 mg) per square meter of body surface. This translates into 500 to 2,000 mg each month as a single intravenous dose.

Less serious complications are as follows.

• Nausea and vomiting, which usually occur after the intravenous doses. Not all patients experience this, and it is usually dose-related. At higher doses, this side effect is more likely to occur. If it happens, simple anti-nausea medication, such as Compazine, often helps to correct the problem.
• Hair loss may occur. This is reversible, generally when the medicine is discontinued.

More serious complications are as follows.

• Infection. Since Cytoxan lowers the white blood cell count, infections may occur. This problem is greater when corticosteroids are given in combination with Cytoxan. If the dose of prednisone is less than 20 mg to 30 mg per day the risk is much less, especially if the white blood cell count is kept in a desirable range of greater than 3,000.
• Bladder. Cytoxan collects in the bladder after it is excreted by the kidneys. There are two potential problems that may occur. One is irritation in the bladder that, if severe, may cause significant bleeding. The second is a small incidence of bladder cancer, which occurs on average 10 years after a course of Cytoxan.
• Malignancy. Other cancers, aside from bladder cancer, may occur after Cytoxan therapy. Most commonly these are blood cancers such leukemia and lymphoma. The risk of these is small but real. Estimates are in the range of one to three percent of patients who receive long term, especially continuous, therapy.
• Reproductive. Cytoxan my cause infertility (inability to have children) in patients receiving this drug, especially women. This is greater for women older than 30 who take the medication for more than one to two years. Sometimes amenorrhea (loss of menstrual periods) occurs, but may not necessarily indicate infertility. After stopping the medication, menstrual cycles may recur. Cytoxan should not be taken during pregnancy, as it may cause birth defects.

Laboratories are checked periodically. The total white blood cell, red blood cell and platelet counts are measured every two weeks initially, especially when the dose is being adjusted. The effect on decreasing white blood cell numbers does not occur until two weeks after starting the drug. The white blood cell numbers may be elevated by simultaneous treatments with steroids; therefore, if the Cytoxan dose is increased or the prednisone dose is decreased, blood cell counts are important to follow. After a stable dose has been achieved, labs are obtained monthly or sometimes less frequently.

In addition to these tests, urinalyses are obtained at the same time. This is to ensure no excessive red blood cells are in the urine, which could indicate bladder irritation mentioned above. Also, once each year, special urine studies may be obtained to evaluate whether any abnormal cells exist that might reflect bladder tumors.

Women should not use this medication unless they are practicing adequate birth control or have no chance of getting pregnant.

Drinking several extra large glasses of water daily helps prevent bladder irritation. This is especially true during hot days when dehydration may be an issue.