Peptide Profile
Fertirelin
A potent GnRH analog designed to support reproductive function in veterinary and research settings
Dose Range
25 micrograms-100 microgramsmg
Frequency
Once daily
Route
Intramuscular injection
Cycle Length
Ongoing/indefinite
Onset
Moderate (1-2 weeks)
Evidence
Moderate
Compound Profile
Scientific & Efficacy Data
C55H76N16O12
Molecular Formula
1153.3 g/mol
Molecular Weight
Variable depending on formulation; sustained-release formulations extend duration
Half-Life
High when administered via injection
Bioavailability
66002-66-2
CAS #
188304
PubChem ID ↗
Developed By · 1980
Research Team
Academic Research Institutions
Primary Benefits
Supports reproductive hormone production
May support reproductive function in research applications
Improves timing of breeding and fertility outcomes
Amino Acid Sequence
pGlu-His-Trp-Ser-Tyr-Leu-Leu-Arg-Pro-Gly-NH2Dosing
How much
do I take?
Timing
Best time to take
Administer Fertirelin 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.
With food?
Fertirelin 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.
If stacking
Fertirelin 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.
Adjusting Your Dose
Increase if
- +You've tolerated the current dose for the recommended period without significant side effects
- +Therapeutic goals haven't been met at the current dose level
- +Your healthcare provider recommends dose escalation based on your response
- +Lab work or clinical assessments support a higher dose
Decrease if
- -Side effects are bothersome or impacting daily life despite management strategies
- -You experience any signs of an adverse reaction
- -Lab results indicate the need for dose reduction
- -Your healthcare provider recommends a lower dose based on your response
Signs of right dose
- ✓Therapeutic goals being met with minimal side effects
- ✓Stable and consistent response to treatment
- ✓Lab values or clinical markers trending in the right direction
- ✓Good tolerance with manageable or absent side effects
Dosing Calculator
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Suitability
Is this
right for me?
Best For
Livestock breeding programs
Fertirelin is particularly well-suited for individuals focused on livestock breeding programs. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Reproductive synchronization in cattle
Fertirelin is particularly well-suited for individuals focused on reproductive synchronization in cattle. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Fertility enhancement in veterinary settings
Fertirelin is particularly well-suited for individuals focused on fertility enhancement in veterinary settings. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Research on reproductive hormone mechanisms
Fertirelin is particularly well-suited for individuals focused on research on reproductive hormone mechanisms. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Consider Alternatives If
Who Should Avoid
Do not use if
- ×Pregnancy (may disrupt existing pregnancy)
- ×Hypersensitivity to GnRH analogs
- ×Active reproductive infections
- ×Concurrent use with certain medications
- ×Undiagnosed reproductive disorders
Use with caution if
- !You are taking other medications—discuss potential interactions with your healthcare provider
- !You have a history of liver or kidney disease
- !You are elderly or have multiple medical conditions
- !You are planning surgery in the near future—inform your surgeon about Fertirelin use
- !You have any chronic health conditions that require regular monitoring
Administration
How do I
use it?
Reconstitution
What you need
- •Fertirelin vial (lyophilized powder or solution)
- •Bacteriostatic water or sterile sodium chloride for reconstitution
- •Alcohol swabs for cleaning vial tops and injection sites
- •Appropriately sized syringes with fine-gauge needles (27-30 gauge)
- •Sharps disposal container
Injection
Route
Subcutaneous injection (into the fatty tissue just under the skin)—allows for consistent absorption and can be self-administered at home after proper training
Best sites
- •Abdomen (stomach area)—at least 2 inches from the belly button, most popular choice for self-injection
- •Front of thighs—middle to upper portion of the outer leg
- •Back of upper arm—outer area (may need assistance from another person)
Technique
- 1.Wash your hands thoroughly with soap and water before handling supplies
- 2.Clean the injection site with an alcohol swab and let it air dry completely
- 3.Pinch a fold of skin at the chosen injection site
- 4.Insert the needle at a 45-90 degree angle (depending on needle length and body composition)
- 5.Inject the medication slowly and steadily over 5-10 seconds
- 6.Release the skin fold and remove the needle, applying gentle pressure with a clean swab
- 7.Rotate injection sites to prevent tissue irritation or lipodystrophy
- 8.Dispose of the needle safely in a sharps container—never recap or reuse needles
Storage
Signs of degradation
Sample Daily Schedule
Safety
Is it
safe?
Safety Profile
Fertirelin is a GnRH agonist developed specifically for veterinary use in livestock, particularly cattle breeding and fertility management. The peptide has been safely used in veterinary medicine for over 40 years with a well-documented safety profile in animals. Important limitation: Fertirelin is NOT approved for human use. All safety and efficacy data comes from veterinary applications in cattle and limited laboratory research. Human safety data is minimal and extrapolation from veterinary use is problematic. The biphasic response (initial hormone surge followed by suppression) must be carefully managed in any application. Individual responses can vary significantly based on age, hormonal status, and concurrent medications.
Fertirelin's safety and efficacy data comes primarily from veterinary medicine, where it has been approved for cattle reproduction since 1981 in Japan. The peptide is 15-20 times more potent than natural GnRH at stimulating LH release. Human clinical data is extremely limited, with no FDA or EMA approval for any human indication.
Common Side Effects
Experienced by some users
Mild discomfort at treatment site
Some users experience mild discomfort, which is among the most commonly reported effects with Fertirelin. This typically resolves within a few days as the body adjusts.
Management: Apply ice if needed. Rotate treatment sites. These symptoms typically improve within the first week of use.
Transient hormone fluctuations
As a GnRH agonist, Fertirelin triggers an initial surge in FSH and LH (flare effect) within the first few days, followed by suppression. This biphasic response occurs in 60-80% of users and is expected. Animals may show increased reproductive behavior for 2-4 days before suppression begins.
Management: This is an expected physiologic response. Monitor for signs of exaggerated reproductive behavior. If using in breeding protocols, time applications accordingly. Discuss timing strategy with your veterinarian to optimize breeding outcomes.
Temporary behavioral changes in animals
Cattle and other livestock frequently show increased mounting behavior, vocalizations, and restlessness during the first 24-72 hours after injection, related to the initial hormone surge. These behavioral changes typically resolve as the flare effect subsides and suppression begins.
Management: Keep animals in secure enclosures during the first 48-72 hours post-injection. Provide adequate space and minimize handling stress. Separate animals if aggressive mounting occurs. These behaviors are temporary and expected, not a sign of adverse reactions.
Mild injection site reactions
Localized inflammation at the injection site occurs in approximately 15-20% of animals. This typically includes mild redness and slight induration that develops within hours and resolves within 3-7 days. Is rarely associated with infection or serious complications.
Management: Rotate injection sites between treatments to different areas of the neck or hindquarters. Use sterile injection technique. Apply ice packs if swelling is moderate. Monitor for signs of infection (increasing warmth, pus, fever). Most reactions resolve without intervention.
Short-term changes in appetite
Some animals experience decreased feed intake for 1-2 days immediately after Fertirelin injection, correlating with the behavioral changes from the initial hormone surge. Feed consumption typically normalizes by day 3-4 as hormone levels stabilize.
Management: Ensure animals have access to water and hay during the first few days. Continue offering feed even if intake is reduced; appetite usually returns spontaneously. Contact your veterinarian if appetite remains reduced beyond 4 days or if the animal appears distressed.
Temporary mood variations
Animals may appear more irritable or aggressive during the 24-72 hour period following injection due to elevated hormones. Restlessness and hyperreactivity are common. These mood changes correlate with the flare effect and typically resolve as LH suppression begins.
Management: Minimize stressful handling and procedures during the first 72 hours post-injection. Provide a calm environment. Avoid mixing treated and untreated animals if aggression is significant. These behavioral changes are temporary and expected with GnRH agonists.
Minimal systemic effects at therapeutic doses
Systemic side effects are uncommon at recommended veterinary doses (25-100 mcg). Most therapeutic responses are localized to reproductive and behavioral systems. Animals rarely show signs of systemic toxicity or off-target organ effects when using proper injection technique and staying within established dosing guidelines.
Management: Maintain strict adherence to veterinary dosing recommendations. Monitor general health status (appetite, activity, temperature) during the first week. Report any unexpected systemic signs (severe lethargy, vomiting, fever) to your veterinarian immediately, though these are rare.
Less Common
- •Occasional swelling at injection site
These typically resolve with continued use or dose adjustment.
Stop and Seek Help If
- ×Severe or worsening side effects that don't improve with dose adjustment or supportive care
- ×Signs of an allergic reaction—rash, hives, swelling, or difficulty breathing
- ×Your healthcare provider recommends discontinuation based on your clinical response
- ×Development of any new medical condition that may be contraindicated with Fertirelin
- ×Pregnancy or planning to become pregnant (unless specifically approved for use during pregnancy)
- ×Abnormal lab results or clinical markers that suggest adverse effects
Fertirelin 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.
Interactions
With other peptides
- ✓May be used together under medical guidance.
- ✓May be used together under medical guidance.
- ✓May be used together under medical guidance.
With medications
- !Dopamine agonists - Use with caution—discuss with your healthcare provider.
- !Other GnRH agonists without medical guidance - Use with caution—discuss with your healthcare provider.
- !Certain anticonvulsants - Use with caution—discuss with your healthcare provider.
With supplements
- ✓Multivitamins - Generally safe to take alongside Fertirelin. Space doses apart if taking oral formulations to ensure optimal absorption.
- ✓Electrolyte supplements - Helpful if experiencing any GI side effects that could lead to dehydration. Safe to combine.
Effectiveness
Does it
work?
Evidence Level
Moderate human trials
What to Expect
0-6 hours
What you might notice
- •GnRH receptors activated, hormone cascade begins
- •Fertirelin binds to pituitary GnRH receptors, triggering follicle-stimulating hormone (FSH) and luteinizing hormone (LH) release
What's normal
- •Initial response to Fertirelin is beginning at the cellular level
- •Different individuals experience Fertirelin's onset at different rates
- •Transient systemic effects from initial Fertirelin exposure are common
What's next
- →Maintain consistent Fertirelin administration as prescribed
- →Document subjective effects and physical markers daily
- →Schedule a check-in with your provider about initial observations
6-24 hours
What you might notice
- •Ovarian response develops
- •Follicle growth accelerates and hormonal support increases, setting the stage for ovulation
What's normal
- •Fertirelin is achieving sufficient receptor engagement
- •Initial mechanism of Fertirelin is taking effect
- •Early transient effects from Fertirelin administration are resolving
What's next
- →Maintain consistent Fertirelin administration as prescribed
- →Document subjective effects and physical markers daily
- →Schedule a check-in with your provider about initial observations
24-72 hours
What you might notice
- •Ovulation occurs
- •Peak hormone surge triggers the release of the egg, allowing for proper timing of insemination
What's normal
- •Fertirelin response patterns are emerging
- •Initial Fertirelin response is consistent with mechanism expectations
- •Early tolerance development to Fertirelin is not expected
What's next
- →Assess whether Fertirelin response aligns with expectations
- →Plan next steps based on initial Fertirelin tolerance and response
- →Establish baseline monitoring for Fertirelin response tracking
Signs It's Working
Treatment Response
- ✓Improvement in the primary symptoms or condition being treated
- ✓Positive changes in relevant lab values or clinical markers
- ✓Consistent, stable response to Fertirelin over time
- ✓Reduction in symptom frequency or severity
General Well-being
- ✓Improved energy levels and daily functioning
- ✓Better quality of life related to the treated condition
- ✓Manageable or absent side effects indicating good tolerance
- ✓Positive feedback from healthcare provider during check-ups
Not Seeing Results?
Common reasons
- •Not at therapeutic dose yet—initial doses are for building tolerance, not maximum effect
- •Insufficient time at target dose—most compounds need several weeks to show full benefits
- •Inconsistent dosing schedule—regular, consistent use is crucial for optimal results
- •Individual variation in response—genetics, metabolism, and other factors affect outcomes
- •Underlying conditions or medications interfering with absorption or effectiveness
- •Improper storage leading to degraded product—always verify proper storage conditions
Key Research
"Effect of fertirelin acetate or buserelin on conception rate at first or second insemination in lactating dairy cows"
Chenault JR, 1990
Finding: Fertirelin acetate improved conception rates in lactating dairy cows when administered for timed insemination. The GnRH agonist effectively synchronized ovulation and improved fertility outcomes in breeding programs.
View Study"Effects of LHRH-analogue treatment of spermatogenic dysfunction in the dog"
Kawakami E, Tonsho H, Tsutsui T, 1991
Finding: LHRH analogs improved sperm quality in dogs by temporarily raising testosterone and LH levels. Treatment restored fertility within 30 days, with sperm abnormalities decreasing from 19-32% to 10-16%.
View Study"Induction of fertile estrus in bitches using a sustained-release formulation of a GnRH agonist (leuprolide acetate)"
Inaba T, Tani H, Gonda M, 1998
Finding: GnRH agonist depot formulations successfully induced fertile estrus in female dogs, allowing precise control of breeding timing. Long-acting formulations provided sustained hormone effects for reproductive management.
View StudyFrequently Asked Questions