Busulfan

Definition

Busulfan (also known by the brand name Myleran) is a chemotherapy medicine used to treat cancer by destroying cancerous cells.

Purpose

Busulfan is approved by the Food and Drug Administration (FDA) to treat chronic myelogenous leukemia (also called chronic myelocytic leukemia). It has also been less commonly used for other acute leukemias and a blood disease known as polycythemia vera, in which there are too many red blood cells. Busulfan is also used in combination with other chemotherapy drugs for a procedure known as bone marrow transplantation.

Description

Busulfan a member of the group of chemotherapy drugs known as alkylating agents. Alkylating agents interfere with the genetic material (DNA) inside the cancer cells and prevent them from further dividing and producing more cancer cells. Busulfan is taken orally and comes in tablet form.

Recommended dosage

Busulfan can be taken following several different dosing schedules, depending on the disease. Busulfan is a 2mg oral tablet, and patients may need to take more than one tablet at a time depending on the dose. The induction or starting dose is 4mg up to 12mg per day. This may then be decreased to 1mg to 3mg per day as a maintenance dose. The dose of busulfan for use in combination with other chemotherapy drugs before a bone marrow transplant is much larger than leukemia dosing. Busulfan, when used for bone marrow transplants, is dosed by patient body weight. Busulfan is usually given at a dose of 4mg per kilogram of body weight each day for 4 days before a bone marrow transplant.

Precautions

Blood counts are monitored regularly while on busulfan therapy. During a certain period of time after receiving busulfan, there is an increased risk of contracting infections. Caution should be taken to avoid unnecessary exposure to bacteria and viruses. All patients should increase their daily fluid intake while receiving this drug.

Patients who are pregnant or are trying to become pregnant should notify their physician before taking busulfan (or any chemotherapy medication). Busulfan causes a high incidence of sterility in males, and has been known to cause sterility in females as well.

Patients with a known previous allergic reaction to chemotherapy drugs, or who suffer from gout, thalassemia, or seizure problems, should notify their physician before beginning treatment. The physician should also be consulted before receiving live virus vaccines while on chemotherapy.

Side effects

The most common side effect expected from taking busulfan is low blood counts, referred to as myelosuppression. Lowering of the white count, or neutropenia, is common and lasts for some time before the white count returns to normal levels. When the white blood cell count is low, patients are at an increased risk of developing a fever and infections. The platelet blood count can also be decreased due to busulfan administration. Platelets are blood cells in the body that cause clots to form; the purpose of these clots is to control bleeding. When the platelet count is low, patients are at an increased risk for both bruising and bleeding. If the platelet count remains too low, a platelet blood transfusion may be an option for treatment. Busulfan also causes low red blood cell counts, or anemia. Low red counts make patients feel tired, dizzy, and fatigued. Erythropoietin is a drug that can be used to increase red blood cell count.

In bone marrow transplant patients, the dose of busulfan that is given in combination with other chemotherapy drugs is intended to cause complete bone marrow destruction prior to bone marrow transplant.

Nausea, vomiting, loss of appetite, mouth sores, and diarrhea are rare side effects from busulfan at normal doses, but are common at the higher doses used for bone marrow transplant. If nausea and vomiting are a problem, patients can be given medications known as antiemetics before receiving busulfan to help prevent or decrease these side effects. Taking busulfan on an empty stomach may also decrease nausea and vomiting.

Damage to nerves and nervous system tissues is uncommon with standard busulfan therapy. However, at high doses, some reports do exist of seizures, dizziness, confusion, and visual disturbances.

Busulfan can also cause severe lung problems known as "busulfan lung". Symptoms include a nonstop cough, shortness of breath, fever, and difficulty breathing.

Less common side effects caused by busulfan include skin rashes or reactions (including darkening of the skin), dryness of the skin, itching, and hair loss (alopecia).

Although it is uncommon, severe liver problems may occur due to busulfan administration at higher doses. Rare reactions to busulfan include: lung problems, cataracts, fatigue, heart problems, low blood pressure, development of another type of cancer or leukemia, enlarged breast tissue (referred to as gynecomastia), and increased uric acid levels (which can lead to kidney problems and gout).

Any side effects experienced by a patient should be reported to his or her physician.

Interactions

Busulfan used for transplant purposes, when given in high doses with the chemotherapy drug cyclophosphamide, caused an increase in serious heart problems.

Patients who have taken busulfan with the drug thioguanine over long periods of time have shown an increase in enlarged veins in the esophagus and liver problems.

KEY TERMS

Anemia

A red blood cell count that is lower than normal

Bone marrow transplant

A procedure that destroys all of a patients' diseased bone marrow and replaces it with healthy bone marrow

Cataract

Formation on the lens of the eye that causes cloudy vision

Chemotherapy

Specific drugs used to treat cancer

Food and Drug Administration

A government agency that oversees public safety in relation to drugs and medical devices

Gout

A disease caused by a buildup of uric acid in the joints causing pain

Hemoglobin

A respiratory pigment in the red blood cells that combines with and transports oxygen around the body

Intravenous

To enter the body through a vein

Metastatic

Cancer that has spread to one or more parts of the body

Neutropenia

A white blood cell count that is lower than normal

Polycythemia vera

A blood disease in which too many red blood cells exist in the body

Thalassemia

A genetic form of anemia that prevents affected individuals from synthesizing hemoglobin properly