Busulfex (busulfan)

Common side effects of Busulfex include:

• nausea,
• vomiting,
• diarrhea,
• constipation,
• loss of appetite,
• weight loss,
• mouth sores,
• upset stomach,
• abdominal pain,
• dizziness,
• weakness,
• swelling of the ankles/feet/hand,
• flushing (warmth,
• redness, or tingly feeling),
• headache,
• trouble sleeping,
• swelling or irritation around the IV needle,
• missed menstrual periods,
• hair loss,
• darkened skin color, and
• fatigue.

Tell your doctor if you have serious side effects of Busulfex including:

• pale skin,
• lightheadedness,
• shortness of breath,
• trouble concentrating,
• easy bruising,
• unusual bleeding,
• purple or red pinpoint spots under your skin,
• signs of infection (such as fever, chills, sore throat, flu symptoms, loss of appetite, weight loss, unusual weakness, mouth and throat ulcers, rapid and shallow breathing),
• weight gain,
• stomach swelling or tenderness,
• yellowing of the skin or eyes (jaundice),
• coughing up blood,
• stomach pain,
• sharp chest pain,
• trouble breathing,
• lower back pain,
• blood in your urine,
• urinating less than usual or not at all,
• confusion,
• jerking muscle movements,
• muscle tightness or contraction,
• overactive reflexes,
• muscle weakness or limp feeling,
• leg discomfort,
• numbness or tingly feeling around your mouth,
• fast/slow/uneven heart rate,
• weak pulse,
• confusion,
• fainting,
• seizures (convulsions),
• persistent cough,
• congestion, or
• low fever

Initial Dosing Information

• Administer Busulfex in combination with cyclophosphamide as a conditioning regimen prior to bone marrow or peripheral blood progenitor cell replacement. For patients weighing more than 12 kg, the recommended doses are:
  • Busulfex 0.8 mg per kg (ideal body weight or actual body weight, whichever is lower) intravenously via a central venous catheter as a two-hour infusion every six hours for four consecutive days for a total of 16 doses (Days -7, -6, -5 and -4).
  • Cyclophosphamide 60 mg per kg intravenously as a one-hour infusion on each of two days beginning no sooner than six hours following the 16^th dose of Busulfex (Days -3 and -2).
  • Administer hematopoietic progenitor cells on Day 0.
• Premedicate patients with anticonvulsants (e.g., benzodiazepines, phenytoin, valproic acid or levetiracetam) to prevent seizures reported with the use of high dose Busulfex. Administer anticonvulsants 12 hours prior to Busulfex to 24 hours after the last dose of Busulfex.
• Administer antiemetics prior to the first dose of Busulfex and continue on a fixed schedule through Busulfex administration.
• Busulfex clearance is best predicted when the Busulfex dose is administered based on adjusted ideal body weight. Dosing Busulfex based on actual body weight, ideal body weight or other factors can produce significant differences in Busulfex clearance among lean, normal and obese patients.

  Men:	IBW (kg)=50+0.91× (height in cm -152)
  Women:	IBW (kg)=45+0.91× (height in cm -152)

  • Calculate ideal body weight (IBW) as follows (height in cm, and weight in kg):
  • For obese or severely obese patients, base Busulfex dosing on adjusted ideal body weight (AIBW):
    • AIBW= IBW +0.25× (actual weight -IBW).

Drugs That Decrease Busulfex Clearance

• Itraconazole decreases busulfan clearance by up to 25%. Metronidazole decreases the clearance of busulfan to a greater extent than does itraconazole; metronidazole coadministration has been associated with increased busulfan toxicity. Fluconazole (200 mg) has been used with Busulfex.
• Decreased clearance of busulfan was observed with concomitant use with deferasirox. The mechanism of this interaction is not fully elucidated. Discontinue iron chelating agents well in advance of administration of Busulfex to avoid increased exposure to busulfan.
• Because busulfan is eliminated from the body via conjugation with glutathione, use of acetaminophen prior to (less than 72 hours) or concurrent with Busulfex may result in reduced busulfan clearance based upon the known property of acetaminophen to decrease glutathione levels in the blood and tissues.

Drugs That Increase Busulfex Clearance

• Phenytoin increases the clearance of busulfan by 15% or more, possibly due to the induction of glutathione-S-transferase. Since the pharmacokinetics of Busulfex were studied in patients treated with phenytoin, the clearance of Busulfex at the recommended dose may be lower and exposure (AUC) higher in patients not treated with phenytoin.

• Busulfex can cause fetal harm when administered to a pregnant woman based on animal data. Busulfan was teratogenic in mice, rats, and rabbits following administration during organogenesis.
• The solvent, DMA, may also cause fetal harm when administered to a pregnant woman.
• It is not known whether Busulfex is present in human milk. Because many drugs are excreted in human milk and because of the potential for tumorigenicity shown for busulfan in human and animal studies, discontinue breastfeeding during treatment with Busulfex.