Denileukin Difitox

Reviewed on 3/27/2023

What Is Denileukin Difitox and How Does It Work?

Denileukin Difitox is a prescription medication used for the treatment of cutaneous T-cell lymphoma

  • Denileukin Difitox is available under the following different brand names: Ontak.

What Are the Side Effects Associated with Using Denileukin Difitox?

Common side effects of Denileukin Difitox include:

  • Fever,
  • Chills,
  • Nausea,
  • Vomiting,
  • Diarrhea,
  • Easy bruising,
  • Unusual bleeding,
  • Blood in the urine,
  • Cloudy urine,
  • Pain or burning with urination,
  • Extreme fatigue,
  • Weakness,
  • Anxiety,
  • Nervousness, and
  • Yellowing of the skin or eyes (jaundice)

Serious side effects of Denileukin Difitox include:

  • Hives,
  • Difficulty breathing,
  • Swelling of the face, lips, tongue, or throat,
  • Dizziness,
  • Sudden swelling,
  • Rapid weight gain,
  • Little or no urine,
  • Shortness of breath,
  • Irregular heartbeats, and
  • Chest pain

Rare side effects of Denileukin Difitox include:

  • None 

Seek medical care or call 911 at once if you have the following serious side effects:

  • Severe headache, confusion, slurred speech, arm or leg weakness, trouble walking, loss of coordination, feeling unsteady, very stiff muscles, high fever, profuse sweating, or tremors;
  • Serious eye symptoms such as sudden vision loss, blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights;
  • Serious heart symptoms include fast, irregular, or pounding heartbeats; fluttering in the chest; shortness of breath; sudden dizziness, lightheadedness, or passing out.

This is not a complete list of side effects and other serious side effects or health problems that may occur because of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.

What Are the Dosages of Denileukin Difitox?

Adult dosage

Single-use vial 

  • 150 mcg/mL (300 mcg in 2 mL).

Cutaneous T-Cell Lymphoma

Adult dosage

  • Administer at 9 or 18 mcg/kg/day by intravenous infusion over 30-60 minutes for 5 consecutive days every 21 days for 8 cycles.

Dosage Considerations – Should be Given as Follows: 

  • See “Dosages”

What Other Drugs Interact with Denileukin Difitox?

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

  • No formal drug-drug interaction studies have been conducted with Denileukin Difitox.

This information does not contain all possible interactions or adverse effects. Visit the RxList Drug Interaction Checker for any drug interactions. Therefore, before using this product, tell your doctor or pharmacist about all your products. Keep a list of all your medications with you and share this information with your doctor and pharmacist. Check with your healthcare professional or doctor for additional medical advice, health questions, or concerns.

What Are Warnings and Precautions for Denileukin Difitox?


  • None

Effects of drug abuse

  • None

Short-Term Effects

  • See “What Are Side Effects Associated with Using Denileukin Difitox?”

Long-Term Effects

  • See “What Are Side Effects Associated with Using Denileukin Difitox?”


  • Infusion Reactions
    • Infusion reactions, defined as symptoms occurring within 24 hours of infusion and resolving within 48 hours of the last infusion in that course, were reported in 70.5% (165/234) of Ontak-treated patients across 3 clinical studies utilizing the approved doses and schedule.
    • Serious infusion reactions were reported in 8.1% (19/234) of Ontak-treated patients. There have been post-marketing reports of infusion reactions resulting in death.
    • For patients completing at least 4 courses of Ontak treatment in Study 1 [see Clinical Studies (14.1)], the incidence of infusion reactions was lower in the 3rd and 4th cycles as compared to the 1st and 2nd cycles of Ontak. 
    • Resuscitative equipment should be available during Ontak administration. Immediately stop and permanently discontinue Ontak for serious infusion reactions.
  • Capillary Leak Syndrome
    • Capillary leak syndrome was defined as the occurrence of at least 2 of the following 3 symptoms (hypotension, edema, serum albumin below 3.0 g/dL) at any time during Ontak therapy. 
    • These symptoms were not required to occur simultaneously to be characterized as capillary leak syndrome. 
    • As defined, capillary leak syndrome was reported in 32.5% (76/234) of Ontak-treated patients. Among these 76 patients with capillary leak syndrome, one-third required hospitalization or medical intervention to prevent hospitalization. 
    • There have been post-marketing reports of capillary leak syndrome resulting in death. The onset of symptoms in patients with capillary leak syndrome may be delayed, occurring up to 2 weeks following infusion. Symptoms may persist or worsen after the cessation of Ontak.
  • Regularly assess patients for:
    • weight gain,
    • new onset or
    • worsening edema, 
    • hypotension (including orthostatic changes) and
    • monitor serum albumin levels prior to the initiation of each course of therapy and more often as clinically indicated. 
    • Withhold Ontak for serum albumin levels of less than 3.0 g/dL.
  • Visual Loss
    •  Loss of visual acuity, usually with loss of color vision, with or without retinal pigment mottling has been reported following administration of Ontak. Recovery was reported in some of the affected patients; however, most patients reported persistent visual impairment.
  • CD25 Tumor Expression and Evaluation
    • Confirm that the patient’s malignant cells express CD25 prior to administration of Ontak. A testing service for the assay of CD25 expression in tumor biopsy samples is available. For information on this service call 877-873-4724.
  • Laboratory Monitoring/Hypoalbuminemia
    • Monitor serum albumin levels prior to the initiation of each treatment course. 
    • Withhold administration of Ontak if serum albumin levels are less than 3.0 g/dL

Pregnancy and Lactation

  • It is not known whether the drug can cause fetal harm when administered to a pregnant woman or can affect reproductive capacity. Animal reproduction studies have not been conducted with the drug. Denileukin Difitox should be given to a pregnant woman only if clearly needed.
  • Lactation
    • It is not known whether the drug is excreted in human milk. Because many drugs are excreted in human milk, and because of the potential for serious adverse reactions in nursing infants from the drug, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.

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