Posted on April 28th, 2009 by

Class: Hormonal Therapy

Generic Name: abarelix

Trade Name: Plenaxis™

***NOTE: This drug is discontinued in the United States. Abarelix (Plenaxis™) was used to treat advanced prostate cancer when other treatments could not be used or were refused. Abarelix was available only from health care providers who participated in a special prescribing program. If you are currently taking abarelix, contact your prescriber for instructions. Your prescriber will provide you with information about which available drug treatment may be best for you.

What is the mechanism of action? Abarelix is referred to as a gonadotropin releasing-hormone (GnRH) antagonist. Gonadotropin releasing hormone is produced by the hypothalamus and stimulates the production of testosterone, a male hormone that is associated with the growth of prostate cancer. Abarelix reduces the ability of GnRH to bind properly to cells, and therefore inhibits the production of testosterone stimulated by GnRH.

How is abarelix typically given (administered)? Abarelix is administered into a muscle (intramuscular).

How are patients typically monitored? Patients will usually have scheduled meetings with their healthcare provider while they are being treated with abarelix.  Typically, blood will be drawn to check levels of testosterone and prostate specific antigen (PSA) before and during therapy and to monitor functions of some organ systems, such as the liver.  Patients may also undergo physical examinations, scans or other measures to assess side effects and response to therapy.

Patients are also monitored for an allergic-type reaction that may be caused by abarelix. Patients may be monitored for at least 30 minutes following administration of abarelix for low blood pressure, hives, rash, or signs of fainting. Patients experiencing difficulty breathing, dizziness, a noticeable change in heart rate or rhythm, extreme lethargy, hives or rash should tell their healthcare provider immediately.

What are the common (occur in 30% or more of patients) side effects of treatment with abarelix?

• Hot flushes
• Sleep disturbances
• Pain
• Breast enlargement

What are the less common (occur in 10% to 29% of patients) side effects of treatment with abarelix?

• Breast pain
• Nipple tenderness
• Back pain
• Constipation
• Swelling of the hands and/or feet
• Dizziness
• Headache
• Upper respiratory infection
• Diarrhea
• Urinary tract infection
• Inability to urinate, low urine volume, frequent urination, painful urination
• Nausea
• Fatigue

What are the potential long-term side effects of treatment with abarelix?

• Decrease in bone mineral density (osteoporosis)

This is not a complete list of side effects. Some patients may experience other side effects that are not listed here. Patients may wish to discuss with their physician the other less common side effects of this regimen, some of which may be serious.

Some side effects may require medical attention. Other side effects do not require medical attention and may go away during treatment. Patients should check with their physician about any side effects that continue or are bothersome.

What can patients do to help alleviate or prevent discomfort and side effects?

• Patients should inform their doctors of any side effects.
• Wear sunscreen and protective clothing; try to minimize sun exposure.
• Drink plenty of fluid.  Patients should ask their physician about the amount of liquid to consume during a day.
• Maintain adequate rest and nutrition.
• Eat small meals frequently to help alleviate nausea
• If experiencing hot flushes, patients may wish to dress cool and remain in a cool environment if possible

Are there any special precautions patients should be aware of before starting treatment?

• Patients should tell their physician if they are pregnant, breastfeeding or planning a family in the near future. This drug may cause birth defects. It is important to use some kind of birth control while undergoing treatment.  Also, patients may want to talk to their physician if they are considering having children in the future, since some drugs may cause fertility problems. Abarelix is not indicated for use in women.
• It is important that patients inform their physician of any pre-existing condition (chicken pox, infection, heart disease, kidney disease, liver disease, lung disease, etc.), as they may worsen with this drug or can affect the doses administered.
• Patients should let their physician know of any other medication they are taking (whether prescription or over the counter, including vitamins, herbs, etc.) as they may interfere with treatment. It is important for patients to inform their physician of any medications they are taking for a heart condition.
• Patients should check with their physician before starting any new drug or nutritional supplement.
• Patients should inform their physician of any known drug or food allergies or any reactions to medications they have experienced in the past.

When should patients notify their physician?

• Signs of an allergic reaction – hives, rash, itching, difficulty breathing, tightness of chest, extreme lethargy, fainting,
• Noticeable change in heart rate or rhythm
• Inability to urinate, pain or burning upon urination, increased frequency of urination, and/or low volumes of urine output
• Swelling of hands or feet, or  facial features
• Cough
• Fever
• Dizziness
• Yellowing of the skin or eyes
• Right upper abdominal pain
• Swelling of the feet and ankles accompanied by sudden weight gain

What is a package insert? 

A package insert is required by the FDA and contains a summary of the essential scientific information needed for the safe and effective use of the drug for healthcare providers and consumers.  A package insert typically includes information regarding specific indications, administration schedules, dosing, side effects, contraindications, results from some clinical trials, chemical structure, pharmacokinetics and metabolism of the specific drug. By carefully reviewing the package insert, you will get the most complete and current information about how to safely use this drug. If you do not have the package insert for the drug you are using, your pharmacist or physician may be able to provide you with a copy.

Copyright © 2016 CancerConnect Last updated 08/16.

Important Limitations of Use

The information provided above on the drug you have selected is provided for your information only and is not a substitute for consultation with an appropriate medical doctor. We are providing this information solely as a courtesy and, as such, it is in no way a recommendation as to the safety, efficacy, or appropriateness of any particular drug, regimen, dosing schedule for any particular cancer, condition or patient nor is it in any way to be considered medical advice. Patients should discuss the appropriateness of a particular drug or chemotherapy regimen with their physician.

As with any printed reference, the use of particular drugs, regimens and drug dosages may become out-of-date over time, since new information may have been published and become generally accepted after the latest update to this printed information. Please keep in mind that health care professionals are fully responsible for practicing within current standards, avoiding use of outdated regimens, employing good clinical judgment in selecting drugs and/or regimens, in calculating doses for individual patients, and verifying all dosage calculations.



The prescribing physician is solely responsible for making all decisions relating to appropriate patient care including, but not limited to, drugs, regimens, dose, schedule, and any supportive care.

Tags: Drug Dictionary, Hormonal Therapy, P

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