Degarelix (Firmagon) For Cancer: Side Effects, Interactions, Uses, Cost

Degarelix (Firmagon) is a type of hormone therapy used to treat advanced prostate cancer.

Keep reading to learn more about this injectable medication, including Degarelix’s side effects, whether it is a type of chemotherapy, medication interactions, and more.

What is Degarelix (Firmagon)?

Degarelix is a drug sold and marketed by Ferring Laboratories. It is currently sold as a brand name only, with no generic alternatives.

Degarelix has been recommended by the FDA for the treatment of advanced-stage prostate cancer. 

All its presentations come in injection vials, which may contain either 120 mg or 80 mg per vial.

Degarelix blocks the synthesis and release of testosterone. This is an alternative therapy to other anti-androgen drugs and surgical castration, which is rarely used anymore.

What is Degarelix used for?

Degarelix has been widely used for different types of advanced prostate cancer. It is an alternative to traditional hormonal treatment and was approved by the FDA for treating prostate cancer in 2008.

Since then, Degarelix has been used for testosterone suppression when it contributes to prostate enlargement.

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What are the side effects of Degarelix?

Data from a recent study reported that Degarelix has almost the same adverse effects as standard hormone therapy. 

In other words, there is no advantage or disadvantage to using Degarelix compared to other anti-androgen treatments.

Mild and moderate Degarelix side effects (more common)Severe Degarelix side effects (not frequent)
Pain at the site of injectionElectric abnormalities in the QT interval
Local erythema, induration, or nodule formationSevere diarrhea
Weight gainAnaphylactic reactions
Transient ALT increases
Tiredness or fatigue
Transient changes in bowel habits

Cardiovascular risks, such as stroke and heart attack, are still unclear. The only adverse defect with a very high incidence is pain at the injection site.

In addition to the study above, we can highlight others carried out at an early stage before receiving FDA approval. Among these tolerability studies, we can mention the following findings:

Injection site pain

Injection site pain is the most common side effect of Degarelix that may occur in 28% of cases. 

These injection site symptoms are mostly transient and considered mild to moderate in intensity. 

Despite the occasional occurrence of pain at the injection site, subcutaneous treatment is well tolerated. 

Patients with one year of treatment generally have no problems leading to discontinuation. Less than 1% of patients were forced to discontinue treatment for this type of adverse effect.

Weight gain

Besides injection site reaction, the most frequent adverse events were weight gain and ALT increases. Thus, special attention should be given to liver health in patients receiving Degarelix.


Some patients may experience chills 5 to 10 hours after administering Degarelix. This symptom usually lasts less than 24 hours. 

When it is severe or lasts for a longer period, it should be evaluated by a specialist. 

Increases in liver enzymes

Increases in liver enzymes, especially ALT, are noticeable in many patients. They are mild to moderate in intensity and usually reversible. They occur in 7% of patients with a standard dose.

Cardiac symptoms

Some patients may also present severe adverse effects, such as abnormalities in the QT interval. 

This occurs very rarely but should be taken into account to avoid complications in patients with a cardiac history.

Other side effects

Other adverse effects some patients have reported include:

  • tiredness
  • fatigue
  • headaches
  • abdominal pain
  • constipation
  • diarrhea
  • nausea

These are less likely and usually not a cause of treatment discontinuation.

Allergic reactions

It is important to talk to your healthcare provider immediately if severe allergic reactions occur. 

Seek immediate medical help if you have excessive itching, trouble breathing, or swelling of the face, lips, tongue, or mouth.

How to reduce Degarelix’s side effects

The main adverse effect of Degarelix is an injection site reaction. This occurs in about 28% of patients and is usually limited to the first testosterone blocker injection.

After the first dose, successive injections have a lower incidence of injection site reactions. A new dose is administered every 28 days, with an incidence of adverse effects of 4% after the first dose.

Therefore, if you experience discomfort at the injection site the first time, you will most likely not experience it again the next time you receive the drug. 

However, here are some recommendations to avoid discomfort at the injection site:

  • Keep the injection site clean at all times. This will avoid any type of contamination that may cause inflammation.
  • Preferably wear loose-fitting clothing. Avoid wearing tight-fitting clothing, especially around the injection area. This will avoid compression or rubbing of the clothing leading to discomfort.
  • Avoid scratching the injection area. In some cases, itching at the injection area may be experienced. If this is the case, it is preferable to use temperature therapy and ointments to relieve the itching rather than actively scratching the area.
  • Avoid re-injecting in the same area where adverse effects have occurred. In the event that you have had any local adverse reaction to the medication, the next dose should be applied in a different area. Avoid re-injecting in the area where these adverse effects occurred. Talk to your doctor if this is the case to make sure the injection is applied in a different zone.

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Interactions with Degarelix

Degarelix does not interfere with CYP430 liver enzymes. Therefore, there are no significant drug interactions with medications metabolized by this enzyme family.

It seems to be free of interactions, except for those associated with additive risk of serious adverse effects. 

In other words, drugs with the same adverse events should be administered with care or avoided altogether.

Contraindicated medical conditions

This recommendation is particularly important in the field of cardiovascular health. 

This drug should not be used in patients with severe renal or hepatic dysfunction. It should also not be used in cardiac patients with a history of QT interval prolongation. 

They are the most important Degarelix warnings, and here’s why:

  • Patients with hepatic dysfunction: The use of Degarelix has been reported to increase liver enzymes. Such increases are mild to moderate, and usually reversible. However, its use should be closely evaluated in patients with severe hepatic insufficiency. It may lead to a worsening of hepatic damage, so its use is not recommended in these cases.
  • Patients with severe renal dysfunction: 20 to 30% of the Degarelix dose is eliminated through the urinary tract. The effects of the drug in patients with severe renal insufficiency have not been extensively studied. Therefore, it is recommended for this type of patient, and if used, it should be with great caution.
  • Patients with QT interval prolongation: It has been shown that the use of Degarelix carries a risk of QT interval prolongation. Patients with underlying cardiac conduction system disease should evaluate their options with their physician to avoid serious adverse effects.
  • Absolute contraindications: there are only two absolute contraindications to the use of Degarelix. One is in pregnancy due to the risk of serious fetal damage. The other is hypersensitivity reactions against the active component.

Drug interactions

Having evaluated the contraindications of Degarelix, we can also infer some drug-drug interactions. 

For example, these medications should be used with great care or avoided if you are consuming Degarelix:

  • Symbicort: This drug contains a combination of budesonide and formoterol. Using it in conjunction with Degarelix can increase your risk of irregular heart rhythm. Its use is associated with abnormalities in electrical conduction in the heart. It may also cause electrolyte disturbances, such as loss of potassium and magnesium through vomiting and prolonged diarrhea.
  • Ventolin: The active component of this drug is albuterol. Like Symbicort, it can also be associated with a risk of irregular heart rhythm. Its use should be monitored, especially in patients with underlying cardiovascular disease.
  • Drugs with a high risk of QT prolongation syndrome: There are many drugs associated with QT prolongation. Some of the better-known include chlorpromazine, haloperidol, levoketoconazole, methadone, procainamide, quinidine, quinine, and sotalol. The combination with Degarelix is not recommended.
  • Drugs with a moderate risk of QT prolongation: Some medications with a moderate risk of QT interval prolongation should be considered, too. For instance, citalopram, domperidone, levofloxacin, and risperidone. If you are taking any of these medications, consult with your physician to evaluate the pros and cons of taking Degarelix as well.
  • Diuretic therapy: Patients receiving diuretic therapy should monitor their electrolyte balance. Some diuretics can cause hypokalemia or hypomagnesemia, which increases the risk of prolongation of the QT interval. Not all diuretics have this effect. Talk to your doctor to find out if you should make any changes to your current treatment.
  • Supplements and herbs associated with QT prolongation: Supplements and herbs to avoid include cinchona, iboga, and licorice extract. If you are taking these supplements or plan to take them, talk to your doctor for advice and recommendations.

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Does degarelix shrink the prostate?

No, Degarelix does not have a mechanism to shrink the prostate. While it is true that PSA levels decrease after Firmagon injections, this is not because the prostate shrinks in size. 

Is degarelix chemotherapy?

No, Degarelix is not a chemotherapeutic. As such, it does not destroy cancer cells.

How do you administer degarelix injections?

Degarelix injections are administered subcutaneously. The first dose is a loading dose, usually 240 mg. 

Thereafter, a new maintenance dose of 80 mg is administered every 28 days. PSA level checks are usually performed in the second month of treatment and then every three months.

The treatment should be administered by a qualified physician using an aseptic technique. After reconstituting the drug, the injection site in the abdomen is selected. 

The injection site is cleaned with an alcohol pad. The needle is then inserted at a 45° angle after pinching and elevating the skin with the thumb and index finger. 

The injection should last 30 seconds. It is normal to produce a lump that corresponds to the deposit of the drug and eventually disappears.

How long does degarelix last?

Each Degarelix injection, as well as the starting dose, lasts for 28 days. After 28 days, you will need a new dose to continue the treatment.

How much does degarelix cost?

Each Firmagon injection costs an estimated $524 per 80 mg injection vial. In some cases, financing programs may apply to patients with insurance. Talk to your doctor to find out what options are available to you.


Firmagon is the trade name of Degarelix. It is a gonadotropin-releasing hormone receptor antagonist. 

The drug is indicated as androgen deprivation therapy in patients with advanced prostate cancer.

It has been approved by the FDA since 2008 and is currently only available as a brand-name drug. 

The medicine is administered subcutaneously every 28 days to reduce testosterone levels and control cancer growth.

Degarelix does not interact with CYP430 family members. Therefore, its pharmacological interactions are concerned with the increased risk of adverse effects.

Firmagon should not be administered in individuals with QT interval prolongation, and drugs with the same side effect should not be administered together. 

Similarly, it also increases liver enzymes and should not be administered in patients with severe hepatic insufficiency.

On the other hand, the most common side effect, present in about 28% of patients, is an adverse reaction at the injection site. 

The most common is pain, but there may also be redness and swelling. These effects are generally limited to the first loading dose and do not recur with successive doses.

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  1. Frampton, J. E., & Lyseng-Williamson, K. A. (2009). Degarelix. Drugs, 69, 1967-1976.
  2. FDA (2015). Highlights of prescribing information for Degarelix. 
  3. Zengerling, F., Jakob, J. J., Schmidt, S., Meerpohl, J. J., Blümle, A., Schmucker, C., … & Kunath, F. (2021). Degarelix for treating advanced hormone‐sensitive prostate cancer. Cochrane Database of Systematic Reviews, (8).

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