Pamorelin (Triptorelin)

GnRH agonist for hormone-dependent cancers, endometriosis, and precocious puberty

Prescription Only (Rx) GnRH Agonist
Active Ingredient
Triptorelin (as embonate)
Available Forms
Powder for depot suspension, Solution for injection
Strengths
3.75 mg depot; 0.1 mg/ml solution
Administration
Intramuscular injection
Known Brands
Gonapeptyl, Pamorelin, Decapeptyl, Trelstar
Manufacturer
Ipsen Pharma
Medically reviewed by iMedic Medical Review Board
Evidence Level 1A

Pamorelin contains triptorelin, a synthetic analogue of gonadotropin-releasing hormone (GnRH). It works by reducing the levels of sex hormones — testosterone in men and estrogen in women. Pamorelin is prescribed for hormone-dependent prostate cancer, early-stage breast cancer in premenopausal women, endometriosis, and central precocious puberty in children. It is given as a monthly intramuscular injection by a healthcare professional.

Quick Facts

Active Ingredient
Triptorelin
Drug Class
GnRH Agonist
Route
IM Injection
Common Uses
Cancer, Endometriosis
Dosing Frequency
Every 4 Weeks
Prescription Status
Rx Only

Key Takeaways

  • Pamorelin (triptorelin) is a GnRH agonist that suppresses sex hormone production, used primarily for prostate cancer, breast cancer, endometriosis, and precocious puberty.
  • It is administered as a monthly intramuscular injection (3.75 mg) by a healthcare professional and requires long-term treatment for cancer indications.
  • An initial “testosterone flare” may occur during the first weeks of prostate cancer treatment — antiandrogen co-therapy may be prescribed to manage this.
  • Common side effects include hot flashes, fatigue, decreased libido, and bone density loss with prolonged use. Depression and cardiac rhythm changes have also been reported.
  • Pamorelin is contraindicated during pregnancy and breastfeeding. Women of childbearing potential must use non-hormonal contraception throughout treatment.

What Is Pamorelin and What Is It Used For?

Quick Answer: Pamorelin (triptorelin) is a GnRH agonist that suppresses the body's production of sex hormones. It is used to treat hormone-dependent prostate cancer, breast cancer in premenopausal women, endometriosis, and central precocious puberty in children.

Pamorelin belongs to a class of medications known as gonadotropin-releasing hormone (GnRH) agonists. The active substance, triptorelin, is a synthetic analogue of the naturally occurring GnRH produced by the hypothalamus. When administered continuously via monthly depot injections, triptorelin initially stimulates the pituitary gland but then causes a phenomenon called receptor downregulation, which ultimately suppresses the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). This leads to a significant reduction in testosterone levels in men and estrogen levels in women.

Prostate Cancer

Pamorelin is widely used in the treatment of hormone-dependent prostate cancer, including locally advanced and metastatic forms. Prostate cancer growth is often driven by testosterone, and by suppressing testosterone to castrate levels, Pamorelin can slow or halt disease progression. It is also used in combination with radiotherapy for the treatment of localized high-risk and locally advanced hormone-dependent prostate cancer, where hormonal suppression combined with radiation has been shown to improve outcomes significantly.

Androgen deprivation therapy (ADT) with GnRH agonists like triptorelin is a cornerstone of prostate cancer management. According to the European Association of Urology (EAU) and National Comprehensive Cancer Network (NCCN) guidelines, ADT is recommended for patients with advanced prostate cancer and as adjuvant therapy alongside radiotherapy for intermediate- and high-risk localized disease. Studies have demonstrated that 2–3 years of ADT in combination with external beam radiotherapy improves overall survival in high-risk patients.

Breast Cancer

In premenopausal women, some breast cancers are driven by estrogen (hormone receptor-positive breast cancer). Pamorelin is used to suppress ovarian function, thereby reducing estrogen levels, as part of the adjuvant treatment for early-stage hormone-dependent breast cancer in premenopausal women who have received chemotherapy. The treatment is used in combination with other hormonal therapies:

  • Tamoxifen — a selective estrogen receptor modulator (SERM), typically prescribed for patients at high risk of recurrence.
  • Aromatase inhibitors (such as letrozole, anastrozole, or exemestane) — which require ovarian suppression to be effective in premenopausal women. Treatment with Pamorelin must begin at least 6–8 weeks before starting an aromatase inhibitor.

Major clinical trials including the SOFT and TEXT trials have shown that ovarian function suppression with a GnRH agonist combined with either tamoxifen or an aromatase inhibitor significantly reduces breast cancer recurrence in premenopausal women with hormone receptor-positive early breast cancer, particularly in those at higher risk.

Endometriosis

Endometriosis is a condition in which tissue similar to the uterine lining grows outside the uterus, causing chronic pelvic pain, painful menstruation, and sometimes infertility. By suppressing estrogen production, Pamorelin creates a temporary “medical menopause” that causes endometrial implants to shrink and symptoms to improve. Treatment with Pamorelin for endometriosis is limited to a maximum of 6 months due to concerns about bone mineral density loss associated with prolonged estrogen suppression.

Central Precocious Puberty

Central precocious puberty (CPP) is the premature onset of puberty (before age 8 in girls and age 10 in boys) caused by early activation of the hypothalamic-pituitary-gonadal axis. Pamorelin is used to suppress the premature release of sex hormones, allowing children to grow at a normal rate and reach their expected adult height. Treatment is continued until the appropriate age for puberty to resume. After discontinuation, puberty progresses normally and fertility is generally preserved.

What Should You Know Before Taking Pamorelin?

Quick Answer: Pamorelin should not be used if you are allergic to triptorelin or other GnRH analogues, during pregnancy or breastfeeding, or for hormone-independent prostate cancer. Important warnings include cardiovascular monitoring, risk of bone density loss, possible depression, and an initial testosterone flare in prostate cancer patients.

Contraindications

Do not use Pamorelin if you have a known allergy to triptorelin, gonadotropin-releasing hormone (GnRH), other GnRH analogues, or any of the excipients in the formulation. Specific contraindications by population include:

  • Men: Pamorelin should not be used for prostate cancer that is not hormone-dependent (hormone-independent or castration-resistant prostate cancer).
  • Women: Pamorelin is contraindicated during pregnancy and breastfeeding. Pregnancy must be excluded before treatment begins.

Warnings and Precautions

Before starting Pamorelin, inform your healthcare provider about all existing medical conditions. The following precautions apply to all patients:

  • Diabetes and metabolic conditions: Blood glucose levels should be monitored during treatment, as GnRH agonists can affect glucose metabolism.
  • Cardiovascular disease: Patients with hypertension or cardiovascular disease should have blood pressure monitored. Pamorelin may increase the risk of cardiac arrhythmias (QT prolongation), especially when used with other QT-prolonging medications.
  • Depression: Depression, which can be severe, has been reported in patients taking Pamorelin. Inform your doctor if you experience feelings of sadness, hopelessness, or mood changes during treatment.
  • Bone density loss: Long-term GnRH agonist therapy can reduce bone mineral density, increasing the risk of osteoporosis and fractures. This risk is greater in patients who smoke, consume excessive alcohol, have a family history of osteoporosis, have poor nutrition, or use anticonvulsants or corticosteroids. Your doctor may perform bone density scans before and during treatment.
  • Seizures: Cases of seizures have been reported with triptorelin, including in patients without a history of epilepsy. Report any seizure activity to your doctor immediately.
  • Pituitary apoplexy: In rare cases, patients with an undiagnosed pituitary adenoma may experience sudden headache, vomiting, visual disturbances, and eye paralysis. This is a medical emergency requiring immediate attention.
  • Anticoagulant therapy: If you take blood thinners, bruising at the injection site may occur with intramuscular administration.

Specific Warnings for Men

During the first weeks of treatment, testosterone levels initially increase before being suppressed. This testosterone flare can temporarily worsen symptoms, including bone pain, urinary obstruction, and in rare cases, spinal cord compression. Your doctor may prescribe an antiandrogen medication (such as bicalutamide or flutamide) during the initial treatment period to counteract this effect.

Pamorelin should not be used after surgical castration (orchiectomy), as triptorelin provides no additional testosterone reduction in this setting. Long-term androgen deprivation therapy with GnRH agonists has been associated with an increased risk of anaemia (decreased red blood cell count).

Specific Warnings for Women

Pregnancy must be ruled out before initiating treatment. During the first month of treatment, menstruation-like bleeding may occur, after which periods typically cease. If bleeding occurs beyond the first month, consult your doctor. Menstruation usually resumes approximately 2 months after the last injection. Non-hormonal contraception must be used throughout treatment and for one month after the last injection, as hormonal contraceptives (such as the pill) are not sufficiently effective during Pamorelin therapy.

Important for Breast Cancer Patients

If you are taking Pamorelin in combination with an aromatase inhibitor, do not stop Pamorelin without consulting your doctor. Discontinuation can cause estrogen levels to rise rapidly. If Pamorelin treatment is stopped, aromatase inhibitor therapy must also be discontinued within one month of the last Pamorelin injection.

Children and Adolescents

In children being treated for central precocious puberty, the treating physician should be informed of any progressive brain tumour, as this may influence treatment decisions. Girls may experience menstruation-like bleeding during the first month of treatment. After treatment ends, pubertal development resumes normally. Limited long-term fertility data are available, though in most girls, regular menstruation begins approximately one year after stopping treatment. Bone mineral density may decrease during treatment but typically returns to normal after discontinuation.

A rare condition called slipped capital femoral epiphysis (a disorder affecting the growth plate of the hip bone) may occur after treatment cessation. Parents should watch for signs such as limping, hip or knee pain, or limited hip mobility. Additionally, if a child experiences severe or recurring headaches, vision problems, or ringing in the ears, seek medical attention immediately, as this may indicate idiopathic intracranial hypertension.

Pregnancy and Breastfeeding

Pamorelin must not be used during pregnancy or breastfeeding. Women of childbearing potential should be thoroughly examined to exclude pregnancy before treatment begins. Non-hormonal contraceptive methods must be used during treatment until menstruation returns after the final injection. Consult your healthcare provider for individualised contraceptive advice.

Driving and Operating Machinery

Pamorelin may cause dizziness, fatigue, or visual disturbances (such as blurred vision) that could impair your ability to drive or operate machinery. If you experience any of these effects, avoid driving or using machinery until they resolve. You are responsible for assessing whether you are fit to perform these activities.

How Does Pamorelin Interact with Other Drugs?

Quick Answer: Pamorelin can interact with medications that affect heart rhythm (QT-prolonging drugs), including antiarrhythmics like amiodarone and sotalol, the antibiotic moxifloxacin, methadone, and antipsychotics. Always inform your doctor about all medications you are taking.

Drug interactions with Pamorelin primarily relate to its potential to affect cardiac conduction, specifically the QT interval on an electrocardiogram (ECG). When Pamorelin is used alongside other medications known to prolong the QT interval, the cumulative risk of potentially dangerous heart rhythm disturbances (arrhythmias) may be increased. Your healthcare provider should carefully evaluate the benefit-risk balance when prescribing Pamorelin with any of these medications.

Major Interactions

The following medications carry the most significant interaction risk when used with Pamorelin due to QT prolongation effects:

Major Drug Interactions with Pamorelin
Drug Class Interaction Risk Level
Amiodarone Antiarrhythmic Combined QT prolongation risk; increased arrhythmia potential High
Sotalol Antiarrhythmic / Beta-blocker Additive QT prolongation; monitor ECG closely High
Quinidine Antiarrhythmic Significant QT prolongation risk High
Procainamide Antiarrhythmic Additive cardiac conduction effects High
Methadone Opioid analgesic QT prolongation; used for pain and opioid dependence treatment High
Moxifloxacin Fluoroquinolone antibiotic Known QT-prolonging fluoroquinolone; additive risk Moderate–High

Other Interactions to Consider

Antipsychotic medications used for serious mental illness may also prolong the QT interval and should be used cautiously alongside Pamorelin. Always provide your healthcare team with a complete list of all medications, supplements, and over-the-counter products you are taking to ensure safe prescribing.

Because Pamorelin suppresses sex hormone production, it may theoretically interact with hormonal medications, including oral contraceptives, hormone replacement therapy, and other GnRH analogues. Hormonal contraceptives are not effective during Pamorelin therapy, which is why non-hormonal contraception is required.

What Is the Correct Dosage of Pamorelin?

Quick Answer: The standard adult dose of Pamorelin is 3.75 mg administered as an intramuscular injection once every 4 weeks. For children with precocious puberty, the dose is weight-adjusted. All injections are given by a healthcare professional.

Pamorelin is always administered by qualified healthcare personnel. The injection is given intramuscularly into the gluteal muscle, alternating between the left and right sides with each injection. The reconstituted suspension must be used immediately after preparation.

Adults

Prostate Cancer

Dose: 3.75 mg triptorelin (1 vial), intramuscular injection once every 4 weeks.

Duration: Long-term treatment. For localized high-risk and locally advanced disease in combination with radiotherapy, the recommended treatment duration is 2–3 years.

Breast Cancer (Premenopausal Women)

Dose: 3.75 mg triptorelin, intramuscular injection once every 4 weeks.

Duration: Treatment may continue for up to 5 years. Used in combination with tamoxifen or an aromatase inhibitor. If an aromatase inhibitor is prescribed, Pamorelin treatment must begin at least 6–8 weeks before starting the aromatase inhibitor (minimum 2 injections at 4-week intervals).

Endometriosis

Dose: 3.75 mg triptorelin, intramuscular injection once every 4 weeks.

Duration: Maximum 6 months. Treatment should not be extended beyond this period due to the risk of bone mineral density loss.

Children (Central Precocious Puberty)

Pamorelin Dosage for Children — Central Precocious Puberty
Body Weight Dose Volume Frequency
Over 30 kg Full dose (3.75 mg) 2 ml (entire vial) Every 4 weeks (28 days)
20–30 kg Two-thirds dose (2.5 mg) 1.3 ml Every 4 weeks (28 days)
Under 20 kg Half dose (1.875 mg) 1 ml Every 4 weeks (28 days)

Elderly Patients

No specific dose adjustment is required for elderly patients. The standard adult dosage applies. However, elderly patients may be at higher risk for cardiovascular side effects and bone density loss, warranting closer monitoring.

Missed Dose

If an injection is missed, contact your healthcare provider as soon as possible to reschedule. Maintaining regular 4-week injection intervals is important for sustained hormone suppression. A delayed injection may allow hormone levels to temporarily rise, potentially affecting treatment efficacy.

Overdose

Pamorelin is administered by healthcare professionals in a controlled setting, making accidental overdose unlikely. In the event of suspected overdose, contact emergency services or a poison control centre for assessment and guidance. No specific antidote is available; treatment would be supportive and symptomatic.

Important: Do Not Stop Treatment Without Medical Advice

Do not discontinue Pamorelin without speaking to your doctor first. This is especially important for breast cancer patients taking Pamorelin with an aromatase inhibitor, as abrupt cessation can cause a rapid rise in estrogen levels. Your doctor will monitor estrogen levels during treatment and advise on appropriate discontinuation timing.

What Are the Side Effects of Pamorelin?

Quick Answer: The most common side effects of Pamorelin include hot flashes, excessive sweating, fatigue, and decreased sex drive. In men, erectile dysfunction and injection site reactions are common. In women treated for breast cancer, joint pain, osteoporosis, insomnia, and depression are frequently reported. Serious but rare effects include allergic reactions, QT prolongation, and pituitary apoplexy.

Like all medicines, Pamorelin can cause side effects, although not everyone experiences them. Side effects vary depending on the indication (prostate cancer, breast cancer, endometriosis, or precocious puberty) and the patient's sex. The frequency categories used below follow standard medical reporting conventions.

Side Effects in Men (Prostate Cancer)

Very Common

Affects more than 1 in 10 patients
  • Hot flashes
  • Fatigue and weakness
  • Excessive sweating
  • Back pain
  • Tingling, prickling, or numbness in the legs
  • Decreased sex drive
  • Erectile dysfunction

Common

Affects 1 in 10 to 1 in 100 patients
  • Nausea, dry mouth
  • Injection site pain, bruising, redness, swelling
  • Oedema (fluid retention)
  • Musculoskeletal pain, limb pain, lower abdominal pain
  • High blood pressure
  • Allergic reaction
  • Weight gain
  • Dizziness, headache
  • Depression, mood changes

Uncommon

Affects 1 in 100 to 1 in 1,000 patients
  • Heart palpitations
  • Tinnitus (ringing in ears), dizziness, visual impairment
  • Abdominal pain, constipation, diarrhoea, vomiting
  • Drowsiness, chills with sweating and fever
  • Elevated liver function tests
  • Weight loss, appetite changes, gout, diabetes, high blood lipids
  • Joint pain, muscle cramps, muscle weakness, bone pain
  • Insomnia, irritability
  • Breast enlargement in men, breast pain, testicular shrinkage
  • Breathing difficulties, acne, hair loss, itching, skin rash
  • Urinary frequency at night, difficulty urinating

Rare

Affects 1 in 1,000 to 1 in 10,000 patients
  • Purple skin discoloration
  • Abnormal eye sensations, visual disturbances
  • Abdominal distension, flatulence, taste changes
  • Chest pain, difficulty standing
  • Influenza-like symptoms, fever
  • Anaphylactic reaction
  • Stiff joints, joint swelling, bone and joint inflammation
  • Memory impairment, confusion
  • Low blood pressure

Frequency Not Known

Cannot be estimated from available data
  • Anaphylactic shock
  • QT prolongation on ECG
  • Malaise, anxiety
  • Angioedema (swelling of face, tongue, throat)
  • Urinary incontinence
  • Pituitary haemorrhage (in patients with pre-existing pituitary tumour)
  • Anaemia (decreased red blood cells)

Side Effects in Women (Breast Cancer)

The following side effects have been observed when Pamorelin is used for breast cancer in combination with either tamoxifen or an aromatase inhibitor:

Very Common

Affects more than 1 in 10 patients
  • Nausea
  • Severe fatigue
  • Joint and muscle pain
  • Osteoporosis (bone density loss)
  • Hot flashes
  • Excessive sweating
  • Insomnia
  • Depression
  • Decreased sex drive, vaginal dryness, painful intercourse
  • Urinary incontinence
  • Elevated blood pressure

Common

Affects 1 in 10 to 1 in 100 patients
  • Diabetes, hyperglycaemia (high blood sugar)
  • Injection site reactions (pain, bruising, redness, swelling)
  • Allergic reaction
  • Bone fractures
  • Blood clot in a blood vessel (thromboembolism)

Uncommon

Affects 1 in 100 to 1 in 1,000 patients
  • Cerebral haemorrhage (bleeding in the brain)
  • Ischaemia (reduced blood supply to the brain or heart)

Rare

Affects 1 in 1,000 to 1 in 10,000 patients
  • QT prolongation on ECG

Side Effects in Women (Endometriosis)

Very Common

Affects more than 1 in 10 patients
  • Sleep disturbances, mood changes
  • Headache
  • Hot flashes
  • Excessive sweating, acne, oily skin
  • Breast changes, painful intercourse, vaginal bleeding, decreased libido
  • Ovarian hyperstimulation, ovarian enlargement, pelvic pain, vaginal dryness

Common

Affects 1 in 10 to 1 in 100 patients
  • Nausea, abdominal pain, stomach discomfort
  • Joint pain, muscle twitching, limb pain
  • Breast pain
  • Injection site reactions
  • Swelling and tenderness, fatigue
  • Allergic reaction, weight gain
  • Depression, nervousness, dizziness

Uncommon

Affects 1 in 100 to 1 in 1,000 patients
  • Palpitations, vertigo
  • Dry eyes, visual impairment
  • Abdominal bloating, vomiting, flatulence, dry mouth, mouth ulcers
  • Weight loss, decreased appetite, fluid retention
  • Back pain, muscle pain
  • Taste changes, reduced sensation, fainting, memory impairment, difficulty concentrating
  • Anxiety, confusion, mood swings
  • Vaginal bleeding irregularities, ovarian cysts, vaginal discharge
  • Breathing difficulties, nosebleeds
  • Hair loss, increased body hair, dry skin, brittle nails, itching, rash

Side Effects in Children (Precocious Puberty)

Very Common

Affects more than 1 in 10 patients
  • Vaginal bleeding in girls (during first month of treatment)

Common

Affects 1 in 10 to 1 in 100 patients
  • Allergic reaction
  • Headache
  • Hot flashes
  • Abdominal pain
  • Injection site reactions (pain, bruising, redness, swelling)
  • Weight gain
  • Acne

Uncommon

Affects 1 in 100 to 1 in 1,000 patients
  • Blurred vision
  • Vomiting, constipation, nausea
  • Malaise, obesity
  • Neck pain, mood changes
  • Breast pain
  • Nosebleeds
  • Itching, rash, hives

Frequency Not Known

Cannot be estimated from available data
  • Anaphylactic shock, seizures
  • Emotional lability, depression, nervousness
  • Visual disturbances, angioedema
  • Muscle pain
  • Elevated blood pressure, altered blood values including hormone levels
  • Idiopathic intracranial hypertension (raised pressure around the brain — symptoms include headache, double vision, and ringing in the ears)
Reporting Side Effects

It is important to report suspected side effects after a medicine has been authorised. This helps to continuously monitor the benefit-risk balance of the medicine. Healthcare professionals and patients are encouraged to report any suspected adverse reactions to their national medicines regulatory authority.

How Should You Store Pamorelin?

Quick Answer: Store Pamorelin below 25°C (77°F), in its original packaging, out of reach of children. The reconstituted suspension must be used immediately. Do not use after the expiry date.

Proper storage of Pamorelin is essential to maintain the medication's effectiveness and safety. Follow these storage guidelines:

  • Temperature: Store at or below 25°C (77°F). Do not freeze.
  • Light and moisture: Keep the product in its original packaging to protect from light and moisture.
  • Accessibility: Store out of the sight and reach of children.
  • Expiry date: Do not use Pamorelin after the expiry date stated on the carton and vial labels (marked “EXP”). The expiry date refers to the last day of that month.
  • After reconstitution: The prepared suspension must be injected immediately. Do not store reconstituted Pamorelin.
  • Disposal: Do not dispose of medicines via wastewater or household waste. Ask your pharmacist how to dispose of medicines no longer needed. These measures help protect the environment.

What Does Pamorelin Contain?

Quick Answer: Each vial of Pamorelin contains triptorelin embonate equivalent to 3.75 mg triptorelin as the active substance. The powder also contains poly(D,L-lactide-co-glycolide), mannitol, carmellose sodium, and polysorbate 80. The solvent is water for injections.

Understanding the full composition of a medication is important for patients with allergies or sensitivities to specific excipients. Pamorelin 3.75 mg consists of two components that are mixed together immediately before injection.

Active Substance

Each vial contains triptorelin embonate equivalent to 3.75 mg triptorelin. After reconstitution with 2 ml of solvent, each millilitre of the prepared suspension contains 1.875 mg of triptorelin. Triptorelin is a synthetic decapeptide analogue of natural gonadotropin-releasing hormone (GnRH), with modifications that make it more resistant to enzymatic degradation than the natural hormone.

Excipients

Pamorelin Excipients (Inactive Ingredients)
Component Ingredient Function
Powder Poly(D,L-lactide-co-glycolide) Biodegradable polymer for sustained release
Powder Mannitol Bulking agent and lyoprotectant
Powder Carmellose sodium Suspending agent
Powder Polysorbate 80 Surfactant and emulsifier
Solvent Water for injections Vehicle for reconstitution

Sodium Content

Pamorelin contains less than 1 mmol (23 mg) of sodium per vial, meaning it is essentially sodium-free. This is relevant for patients on sodium-restricted diets.

Appearance and Packaging

The powder is a white to off-white powder, and the solvent is a clear solution. Pamorelin 3.75 mg is available in the following pack sizes:

  • 1 vial + 1 ampoule + 1 blister containing 1 syringe and 2 needles
  • 3 vials + 3 ampoules + 3 blisters, each containing 1 syringe and 2 needles

Not all pack sizes may be marketed in all countries.

Frequently Asked Questions About Pamorelin

Pamorelin (triptorelin) is a GnRH agonist used to treat hormone-dependent prostate cancer (locally advanced and metastatic), early-stage hormone-dependent breast cancer in premenopausal women who have received chemotherapy, endometriosis (for symptom relief), and central precocious puberty in children. It works by suppressing sex hormone levels — testosterone in men and estrogen in women — through desensitization of pituitary GnRH receptors.

Pamorelin is given as an intramuscular injection into the gluteal muscle once every 4 weeks (28 days). The injection is always administered by a healthcare professional. The powder must be reconstituted with the provided solvent immediately before use, and the prepared suspension must be injected within 1 minute of reconstitution. Injections are alternated between the left and right gluteal muscles.

The most common side effects (affecting more than 1 in 10 patients) vary by indication. In men with prostate cancer, they include hot flashes, fatigue, excessive sweating, back pain, tingling or numbness, decreased sex drive, and erectile dysfunction. In women treated for breast cancer, common effects include nausea, fatigue, joint and muscle pain, bone density loss, hot flashes, insomnia, depression, vaginal dryness, and elevated blood pressure. In children, vaginal bleeding during the first month is the most common effect in girls.

No. Pamorelin is contraindicated during pregnancy and breastfeeding. Women of childbearing potential must have pregnancy excluded before starting treatment and must use non-hormonal contraception throughout treatment and for one month after the last injection. Hormonal contraceptives (including the pill) are not reliable during Pamorelin therapy because the drug itself suppresses the hormonal axis.

During the first 1–2 weeks of treatment, Pamorelin causes a temporary increase in testosterone levels known as a “testosterone flare.” This can temporarily worsen symptoms such as bone pain, urinary difficulties, and in rare cases, spinal cord compression or leg weakness. To prevent flare-related complications, your doctor may prescribe an antiandrogen medication (such as bicalutamide) to be taken before and during the initial weeks of Pamorelin therapy. After the flare period, testosterone drops to castrate levels.

Treatment duration depends on the condition being treated. For prostate cancer, treatment is typically long-term and may be indefinite for advanced disease, or 2–3 years when combined with radiotherapy for localized high-risk disease. For breast cancer, treatment may continue for up to 5 years. For endometriosis, treatment is limited to a maximum of 6 months to minimise bone density loss. For precocious puberty, treatment continues until the appropriate age for normal puberty to begin.

References

This article is based on the following peer-reviewed sources and international medical guidelines:

  1. European Medicines Agency (EMA). Pamorelin (triptorelin) — Summary of Product Characteristics. Available at: www.ema.europa.eu.
  2. National Comprehensive Cancer Network (NCCN). NCCN Clinical Practice Guidelines in Oncology: Prostate Cancer, Version 4.2025. Available at: www.nccn.org.
  3. Bolla M, de Reijke TM, Van Tienhoven G, et al. Duration of androgen suppression in the treatment of prostate cancer. N Engl J Med. 2009;360(24):2516–2527. doi:10.1056/NEJMoa0810095.
  4. Francis PA, Pagani O, Fleming GF, et al. Tailoring Adjuvant Endocrine Therapy for Premenopausal Breast Cancer. N Engl J Med. 2018;379(2):122–137. doi:10.1056/NEJMoa1803164.
  5. European Association of Urology (EAU). Guidelines on Prostate Cancer, 2024 Edition. Available at: uroweb.org/guidelines.
  6. World Health Organization (WHO). WHO Model List of Essential Medicines, 23rd List (2023). Available at: www.who.int.
  7. British National Formulary (BNF). Triptorelin. National Institute for Health and Care Excellence (NICE). Available at: bnf.nice.org.uk.
  8. Carel JC, Eugster EA, Rogol A, et al. Consensus Statement on the Use of Gonadotropin-Releasing Hormone Analogs in Children. Pediatrics. 2009;123(4):e752–e762. doi:10.1542/peds.2008-1783.
  9. Brown J, Pan A, Hart RJ. Gonadotrophin-releasing hormone analogues for pain associated with endometriosis. Cochrane Database Syst Rev. 2010;(12):CD008475. doi:10.1002/14651858.CD008475.pub2.
  10. Cardoso F, Kyriakides S, Ohno S, et al. Early Breast Cancer: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up. Ann Oncol. 2019;30(8):1194–1220. doi:10.1093/annonc/mdz173.

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