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Bexarotene

Bexarotene

Bexarotene—First Clinical Results Highlight Contradictions | ALZFORUM

Bexarotene is a retinoid drug used for cutaneous manifestations of T-cell lymphoma in patients who have not responded well to previous systemic therapyBexarotene (Targretin) is an antineoplastic agent indicated by the FDA for Cutaneous T cell lymphoma. It has been used off-label for lung cancer, breast cancer, and Kaposi’s sarcoma.Used orally for the treatment of skin manifestations of cutaneous T-cell lymphoma (CTCL) in patients who are refractory to at least one prior systemic therapy. Also used topically for the treatment of skin lesions in early (stage IA and IB) CTCL in patients who experience refractory or persistent disease with the use of other therapies or are intolerant of other therapies.

Bexarotene is a member of a subclass of retinoids that selectively activate retinoid X receptors (RXRs). These retinoid receptors have biologic activity distinct from that of retinoic acid receptors (RARs). Bexarotene is indicated for the treatment of cutaneous manifestations of cutaneous T-cell lymphoma in patients who are refractory to at least one prior systemic therapy. Bexarotene selectively binds and activates retinoid X receptor subtypes (RXRα, RXRβ, RXRγ). RXRs can form heterodimers with various receptor partners such as retinoic acid receptors (RARs), vitamin D receptor, thyroid receptor, and peroxisome proliferator activator receptors (PPARs). Once activated, these receptors function as transcription factors that regulate the expression of genes that control cellular differentiation and proliferation. Bexarotene inhibits the growth in vitro of some tumor cell lines of hematopoietic and squamous cell origin. It also induces tumor regression in vivo in some animal models.

Bexarotene selectively binds with and activates retinoid X receptor subtypes. There are three subtypes in total: RXRα, RXRβ, RXRγ. The exact mechanism of action of bexarotene in the treatment of CTCL is unknown but the drug has activity in all clinical stages of CTCL.

Urinary elimination of bexarotene and its known metabolites is a minor excretory pathway (<1% of administered dose).

Bexarotene is indicated for the treatment of cutaneous manifestations of cutaneous T-cell lymphoma in people who are refractory to at least one prior systemic therapy (oral) and for the topical treatment of cutaneous 

lesions in patients with CTCL who have refractory or persistent disease after other therapies or who have not tolerated other therapies.

Important things to remember about the side effects of bexarotene:

  • Most people do not experience all of the side effects listed.
  • Side effects are often predictable in terms of their onset and duration.
  • Side effects are almost always reversible and will go away after treatment is complete.
  • There are many options to help minimize or prevent side effects.
  • There is no relationship between the presence or severity of side effects and the effectiveness of the medication.
  • The side effects of bexarotene and their severity depend on how much of the drug is given.  (In other words, high doses may produce more severe side effects).

The following side effects are common (occurring in greater than 30%) for patients taking bexarotene:

  • Blood test abnormalities: Elevated blood lipid levels (including cholesterol and triglycerides).
  • Headache.

These are less common (occurring in 10-29%) side effects for patients receiving bexarotene:

  • Blood test abnormalities: Low thyroid hormone levels 
  • Weakness
  • Rash, dermatitis or dry skin 
  • Lowered white blood cell levels (This can increase your risk for infection).
  • Nausea
  • Infection
  • Swelling of the hands or feet
  • Chills (see flu like symptoms)
  • Abdominal pain
  • Cataracts (some evidence of new or worsening of existing cataracts) (see eye problems).
  • Sensitivity to sunlight (photosensitivity) (see skin reactions).

Not all side effects are listed above. Some that are rare (occurring in less than 10% of patients) are not listed here.  However, you should always inform your health care provider if you experience any unusual symptoms.

When to contact your doctor:

Contact your health care provider immediately, day or night, if you should experience any of the following symptoms:

  • Fever of 100.4(F (38 C or higher) or chills (possible signs of infection)

The following symptoms require medical attention, but are not an emergency.  Contact your health care provider within 24 hours of noticing any of the following:

  • Headache (moderate to severe)
  • Nausea (interferes with ability to eat and unrelieved with prescribed medication).
  • Vomiting (vomiting more than 4-5 times in a 24 hour period)
  • Diarrhea (4-6 episodes in a 24-hour period)
  • Changes is vision
  • Swelling in feet or hands
  • Extreme weakness or fatigue (interfering with ability to do daily activities).

Always inform your health care provider if you experience any unusual symptoms.

Precautions:

  • Before starting bexarotene treatment, make sure you tell your doctor about any other medications you are taking (including prescription, over-the-counter, vitamins, or herbal remedies).  Do not take aspirin, products containing aspirin unless your doctor specifically permits this.
  • The manufacturer recommends limiting vitamin A supplementation less than 15,000IU/day but you should discuss taking any vitamin supplements with your doctor BEFORE you take them.
  • Do not receive any kind of immunization or vaccination without your doctor’s approval while taking bexarotene.
  • Inform your health care professional if you are pregnant or may be pregnant prior to starting this treatment.  Pregnancy category X (Bexarotene capsules may cause fetal harm when given to a pregnant woman.  This drug must not be given to a pregnant woman or a woman who intends to become pregnant.  If a woman becomes pregnant while taking bexarotene, the medication must be stopped immediately and the woman given appropriate counseling).
  • Because of the extremely high risk that a deformed infant can result if pregnancy occurs while taking bexarotene in any amount even for short periods of time, for both men and women: Do not conceive a child (get pregnant) while taking bexarotene. Two methods of effective contraception are recommended for women of childbearing potential, unless absolute abstinence is the chosen method.  Discuss with your doctor when you may safely become pregnant or conceive a child after therapy.
  • Do not breast feed while taking this medication.

Self-Care Tips:

  • Take this medication at about the same time every day along with a meal that includes some fats.
  • Avoid grapefruit juice.
  • Drink at least two to three quarts of fluid every 24 hours, unless you are instructed otherwise.
  • You may be at risk of infection so try to avoid crowds or people with colds, and report fever or any other signs of infection immediately to your health care provider.
  • Wash your hands often
  • For flu-like symptoms, keep warm with blankets and drink plenty of liquids.  There are medications that can help reduce the discomfort caused by chills.
  • To reduce nausea, take anti-nausea medications as prescribed by your doctor, and eat small, frequent meals. 
  • Avoid sun exposure.  Wear SPF 15 (or higher) sunblock and protective clothing.
  • In general, drinking alcoholic beverages should be kept to a minimum or avoided completely.  You should discuss this with your doctor.
  • Get plenty of rest 
  • Maintain good nutrition
  • If you experience symptoms or side effects, be sure to discuss them with your health care team.  They can prescribe medications and/or offer other suggestions that are effective in managing such problems.

Monitoring and Testing:

You will be monitored regularly by your health care professional while you are taking bexarotene to monitor side effects and check your response to therapy.  For women of child-bearing age, a pregnancy test is required one week prior to beginning this therapy and every month during treatment.  Blood counts and lipid (fats, cholesterol) levels, liver function and thyroid gland function all need to be analyzed before treatment begins and regularly during treatment.  These are measured through blood tests.

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