Hormones
A lab-made hormone signal that shuts down sex-hormone production, used to treat prostate cancer, endometriosis, and infertility.
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Buserelin is a hormone-suppressing drug used for prostate cancer, endometriosis, and IVF preparation. It is a lab-made copy of GnRH, the brain signal that drives sex hormone production; constant exposure to it shuts that system down, lowering testosterone or estrogen to very low levels — reversibly. It is not FDA approved in the US, but it is approved in Canada as Suprefact and has more than 40 years of clinical use.
Buserelin is a lab-made copy of GnRH, the signal the brain uses to tell the body to make sex hormones. At first it pushes hormone levels up, but after one to two weeks of constant exposure the system shuts down, and testosterone or estrogen drops to very low levels. For endometriosis, that steep drop in estrogen shrinks the misplaced tissue and eases pain; the same shutdown is used for prostate cancer and in IVF. It comes as an injection or a nasal spray, and hormone levels return to normal once treatment stops.
Buserelin is a man-made peptide of nine amino acids and a GnRH agonist (a drug that copies GnRH, the brain's hormone signal). It has D-serine swapped in at position 6. At first it switches the signal on and causes a release of FSH and LH (hormones that tell the testes or ovaries to make sex hormones). This is the flare, lasting 7-14 days. Then the receptors stop responding (desensitization) and drop in number (downregulation (dials down activity)). Within 3-4 weeks this brings testosterone and estrogen down by 90%+.
Evidence check
Well studied in people
This has been through large human trials — the strongest kind of evidence. Scientists have tested it on many people and measured what actually happened.
Every numbered marker on this page links to one of the 5 sources at the bottom.
Hormone Suppression
Reversible hormone suppression after treatment stops
Cancer Management
Suppresses testosterone to near-castrate levels for prostate cancer management
Fertility Support
Improves fertility outcomes when combined with IVF protocols
The most-asked question
The research-reported range is 200 mcg, once daily. Studies used different doses for different situations — find yours:
Prostate cancer (initiation)
500 mcg
The product label starts prostate cancer treatment with 500 mcg under the skin every 8 hours for the first week 5.
Prostate cancer (maintenance), Endometriosis
200 mcg
After the first week, the label switches to 200 mcg once daily under the skin for ongoing treatment 5.
Prostate cancer (maintenance), Needle-free option
400 mcg (2 sprays per nostril)
The nasal spray option delivers 400 mcg three times a day as maintenance, an alternative to daily injections 5.
Prostate cancer (long-term), Convenience
6.3 mg
A long-acting implant placed under the skin slowly releases buserelin over about 2 months, so no daily dosing is needed 5.
Prostate cancer (long-term), Fewer clinic visits
9.45 mg
A larger implant lasts about 3 months between placements 5.
The ceiling: 1,500 mcg (as determined by your healthcare provider based on individual response and tolerance)
Reconstitution, in plain words
Peptides usually arrive as a freeze-dried powder in a small vial. “Reconstitution” just means adding sterile water back in so you can measure a dose. Here's how it works for Buserelin:
Add the recommended volume of bacteriostatic water to the Buserelin vial. Gently swirl (do not shake) until the powder is fully dissolved. The resulting solution should be clear. Calculate your individual dose based on the concentration and your prescribed amount.
Your dose of Buserelin is determined by your healthcare provider. Using an insulin syringe marked in units, draw up the exact amount prescribed. For example, if the reconstituted concentration is 1mg/mL and your dose is 0.5mg, draw up 0.5mL (50 units on an insulin syringe). Always double-check calculations before injection.
Three quick questions — your vial, your water, your dose — and it tells you the exact syringe mark. “Find dose amount” is preloaded with Buserelin's recorded schedule.
Injection sites & technique
Subcutaneous (under the skin) injection (into the fatty tissue just under the skin)—allows for consistent absorption and can be self-administered at home after proper training
Timing
Administer Buserelin at the same time each day (or on the same day each week for weekly injections). Many users prefer morning or evening administration. Pick a time you'll remember consistently.
Buserelin injections can be given regardless of meal timing. However, if GI effects occur, administering on an empty stomach or with a light meal may help reduce discomfort.
Buserelin should be used as directed by your healthcare provider. If combining with other medications or supplements, discuss potential interactions with your provider. Avoid combining with compounds that have overlapping mechanisms unless specifically guided by a medical professional.
Week by week
Is it right for you?
Buserelin should only be started, adjusted, or discontinued under medical supervision. This information is for educational purposes only and does not replace professional medical advice. Never stop a prescribed treatment without consulting your healthcare provider first, as abrupt discontinuation may have consequences.
Use with caution—discuss with your healthcare provider.
Use with caution—discuss with your healthcare provider.
May be used together under medical guidance.
May be used together under medical guidance.
May be used together under medical guidance.
Generally safe to take alongside Buserelin. Space doses apart if taking oral formulations to ensure optimal absorption.
Helpful if experiencing any GI side effects that could lead to dehydration. Safe to combine.
Buserelin is particularly well-suited for individuals focused on managing advanced prostate cancer. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Buserelin is particularly well-suited for individuals focused on treating endometriosis and reducing associated pain. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Buserelin is particularly well-suited for individuals focused on optimizing ovarian response during fertility treatments. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Buserelin is approved in Canada and Europe (not in the US). It works by overstimulating and then shutting down the brain signal (GnRH) that drives testosterone and estrogen production, and its safety data come from Phase 3 trials and decades of clinical use — but deliberately shutting down these hormones carries well-documented risks. The initial testosterone spike (first 2-3 weeks) can worsen prostate cancer symptoms and cause a flare of tumor pain in 10-20% of patients. Long-term use thins bones by 2-3% a year, with spine fractures in 10-20% of long-term users. Heart risks include more heart attacks and strokes in men over 65. Hot flashes affect 40-80%, erection problems are nearly universal, and liver enzyme rises (a sign of liver stress) occur in 5%. The nasal spray form irritates the nose in 20-30% of users.
Buserelin went through Phase 3 clinical trials before approval in Canada and Europe (it has never been FDA approved), and has decades of safety tracking since reaching the market. The initial hormone spike, bone loss, heart effects, and hormone-related complications are well understood from studies spanning over 30 years. Compared with the newer blocking-type drugs (GnRH antagonists (compounds that block a receptor)), buserelin has the disadvantage of that initial spike but a similar long-term side effect profile.
Keeping it good
Store Buserelin in the refrigerator at 36-46°F (2-8°C) in its original packaging. Protect from light and moisture. Do not freeze. Check the expiration date before use. Some formulations may be stored at room temperature for limited periods—check your specific product labeling.
Once reconstituted, Buserelin should be kept refrigerated at 36-46°F (2-8°C) and used within the timeframe specified on your product labeling (typically 14-28 days). Label the vial with the reconstitution date. Do not use if the solution appears cloudy, discolored, or contains particles.
Not our opinion — the published record
1990
Buserelin effectively suppressed natural hormone surges during fertility treatment, allowing doctors to better control egg production timing. A simplified single daily 600 mcg injection proved as effective as more complex dosing schedules.
PubMed Central
2022
Buserelin achieved testosterone suppression below 50 ng/dL within one month, with long-term survival rates of 42-84% depending on treatment approach. When combined with other therapies, survival improved further to 87% in some patient groups.
Raja T, Sud R, Addla S
2023
Real-world data showed buserelin had higher cardiovascular complication rates (9%) compared to modern antagonists. Patients under 65 years experienced very low cardiovascular risk, while older populations showed significant complications requiring monitoring.
Cicione A, Nacchia A, Guercio A
2025
Buserelin showed different side effect patterns than other GnRH agonists (similar hormone-blocking drugs), with more stomach and gut problems. Children had fewer serious side effects than adults, so they need different safety monitoring.
Chen Y, Lu W, Liao R
2015
Prostate cancer dosing: 500 mcg injected under the skin every 8 hours for 7 days, then 200 mcg injected under the skin daily or 400 mcg as a nasal spray three times daily. Slow-release implants placed under the skin come as 6.3 mg (lasts 2 months) and 9.45 mg (lasts 3 months).
Sanofi-aventis Canada Inc.
If this isn't the right fit
Your questions
You'll see some effects within 1-2 weeks, but full benefits take 4-6 weeks. For fertility, timing is precise—ovulation is prevented within days. For cancer, it takes several weeks to see tumor response.
Yes! Once you stop taking it, your hormone levels return to normal within 4-8 weeks. Sexual function, mood, and energy improve as hormones bounce back.
Most people say the injection is a quick pinch, similar to other shots. Some experience minor bruising or redness at the injection site. Your doctor can show you proper injection technique to minimize discomfort.
For men with prostate cancer: fertility may be affected, but hormones usually recover after treatment stops. For women with endometriosis: buserelin actually improves fertility by reducing pain and improving egg quality during IVF. Talk to your doctor about your specific situation.
Yes, the nasal spray works just as well if you use it correctly. You need to spray more frequently (usually 3 times per day), but hormone suppression is equally effective. Some people prefer it because there are no needles.
Hair loss is not a common side effect of buserelin. You might notice some thinning due to hormone suppression, but it's usually temporary and mild compared to chemotherapy.
For endometriosis, doctors typically limit it to 6-12 months due to bone loss risk. For prostate cancer, you might take it indefinitely. For fertility, it's only a few weeks. Your doctor will determine what's safe for your situation.
Not under the brand name Suprefact. However, similar drugs that work on the same brain signal (GnRH agonists (compounds that switch a receptor on)), like leuprolide (Lupron) and goserelin (Zoladex), are available in the US and work the same way.
5 sources
Every numbered marker on this page points to one of these. Same sources, same numbering as the Buserelin research profile on Peptide Initiative.
Want the deep science?
Every claim on this page traces back to the research database behind Peptide Initiative — studies, citations, clinical trial data, and the technical detail we deliberately left out here.
Open the research profileThis guide is education, not medical advice. Talk to a clinician before taking anything.
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