peptideNot FDA-approvedResearch chemicalSerelaxin (recombinant relaxin-2) was studied in a phase III trial but was not granted FDA approval
Relaxin-2Benefits, Dosage & Interactions
Relaxin-2 is a peptide hormone, a naturally occurring biochemical compound composed of amino acid chains linked by peptide bonds. It is the most extensively studied member of the relaxin family of peptides. Research on Relaxin-2 focuses on tissue recovery. Relaxin-2 is administered by injection rather than orally.
How much Relaxin-2 do people take?
30 mcg/kg/day of serelaxin (recombinant human relaxin-2) in the RELAX-AHF trial. Route reported: Intravenous infusion in the hospital setting. Frequency reported: Continuous IV infusion for 48 hours. These are amounts documented in the cited studies and labels for Relaxin-2 — they are reported for reference, not a recommendation. Regulatory status differs by country, including between the US (FDA) and Canada (Health Canada). Confirm any amount with a licensed clinician before you take it.
See the full reported protocol and its sourcesResearched by DoseRoutine Research TeamReviewed for accuracy by Nicholas Alexander, RSE, SO, PMPLast updated Educational reference only — not medical advice. Always confirm dosing and safety decisions with a licensed clinician.
Evidence: Moderate — One published human randomized trial; results not yet replicated.
Evidence strengthModerate · 3/4
PreclinicalStrong human evidence
One published human randomized trial; results not yet replicated.
Plasma half-life
Short plasma half-life of a few minutes, requiring continuous infusion
Default unit
mg
What published protocols report
Ranges documented in the literature, shown for reference. DoseRoutine does not recommend an amount — your prescriber or the product label sets the dose.
- Reported amounts
- 30 mcg/kg/day of serelaxin (recombinant human relaxin-2) in the RELAX-AHF trial[1]
- Route studied
- Intravenous infusion in the hospital setting[1]
- Frequency
- Continuous IV infusion for 48 hours[1]
- Cycle length
- 48-hour infusion during acute hospitalization for heart failure[1]
- Half-life
- Short plasma half-life of a few minutes, requiring continuous infusion[1]
- Storage
- Refrigerated, reconstituted immediately before infusion in the trial setting[1]
Reported for Relaxin-2 in the cited sources. Published ranges are not dosing advice.
Mixing Relaxin-2: bacteriostatic water and syringe units
The vial arrives as dry powder. How much water you add sets the strength, and the strength sets the mark you draw to on the syringe. The table assumes a 5 mg vial and a 250 mcg example draw on a U-100 insulin syringe, where 100 units is one millilitre. If your vial is a different size, scale it — the arithmetic is the same.
| Bacteriostatic water added | Resulting strength | 250 mcg draws to |
|---|---|---|
| 1 mL | 5 mg/mL | 5 units |
| 2 mL | 2.5 mg/mL | 10 units |
| 3 mL | 1.67 mg/mL | 15 units |
Units, not millilitres. Insulin syringes are marked in units, and mixing up mcg and mg on a peptide label is the single most common error people report. Check the label twice. Run your own vial through the calculator.
Storage and stability
- Before mixing
- Sealed and still as a dry powder, Relaxin-2 vials are normally kept in the fridge at 2–8 °C, out of light. Short spells at room temperature during shipping are the norm for lyophilized peptides and are not, on their own, a sign the vial is spoiled.
- After mixing
- Once bacteriostatic water goes in, the vial belongs in the fridge and is generally treated as good for about 28 days — that is how long the benzyl alcohol in bacteriostatic water is relied on to hold back bacterial growth. Plain sterile water has no preservative, so a vial mixed with it is a single-session vial. Never freeze a reconstituted vial.
- When to throw it out
- A properly mixed vial is clear. Cloudiness, floating strands, a color change or powder that will not go into solution after gentle swirling all mean the vial should be discarded rather than used. Shaking a peptide vial hard is the usual cause — swirl it, or run the water down the inside wall of the vial instead of onto the powder.
Handling and shelf-life figures describe general practice for lyophilized peptides. They are not a dose and not medical advice — your prescriber or the product label sets the amount.
References & evidence
Documents the Relaxin-2 entry is written from. Each number matches an inline marker above.
- [1]Serelaxin, recombinant human relaxin-2, for treatment of acute heart failure (RELAX-AHF): a randomised, placebo-controlled trialTeerlink JR, Cotter G, Davison BA, Felker GM, Filippatos G, Greenberg BH, Ponikowski P, Unemori E, Voors AA, Adams KF Jr, Dorobantu MI, Grinfeld LR, Jondeau G, Marmor A, Masip J, Pang PS, Werdan K, Teichman SL, Trapani A, Bush CA, Saini R, Schumacher C, Severin TM, Metra M, RELAXin in Acute Heart Failure (RELAX-AHF) Investigators · The Lancet · 2013 · Peer-reviewed · PMID 23141816
- [2]Cardiovascular effects of relaxin-2: therapeutic potential and future perspectivesAlmeida-Pinto N, Dschietzig TB, Brás-Silva C, Adão R · Clinical Research in Cardiology · 2024 · Peer-reviewed · PMID 37721595
- [3]Relaxin-2 as a Potential Biomarker in Cardiovascular DiseasesAragón-Herrera A, Feijóo-Bandín S, Anido-Varela L, Moraña-Fernández S, Roselló-Lletí E, Portolés M, Tarazón E, Gualillo O, González-Juanatey JR, Lago F · Journal of Personalized Medicine · 2022 · Peer-reviewed · PMID 35887517
What is Relaxin-2 studied for?
What is Relaxin-2?
Relaxin-2 is a peptide hormone, a naturally occurring biochemical compound composed of amino acid chains linked by peptide bonds. It is the most extensively studied member of the relaxin family of peptides. In humans, Relaxin-2 is primarily produced by reproductive organs, especially during pregnancy in the corpus luteum, placenta, and decidua. However, it is also expressed in other tissues, including the heart, brain, and kidneys, suggesting broader physiological roles beyond reproduction (PubChem, NIH ODS). Its primary function is associated with collagen remodeling, angiogenesis (formation of new blood vessels), and anti-inflammatory processes.
Historically, relaxins were first identified for their role in facilitating parturition (childbirth) by relaxing the pubic symphysis and softening the cervix. Subsequent research has unveiled a more extensive range of actions for Relaxin-2, particularly its involvement in connective tissue metabolism, systemic hemodynamics, and protection against fibrosis in various organs. Due to its multifaceted biological activities, Relaxin-2 has garnered interest for its potential therapeutic applications in conditions characterized by fibrosis, inflammation, and tissue remodeling (DrugBank). Its half-life in the human body is approximately 8 hours, meaning it takes about 8 hours for half of the administered substance to be eliminated from the bloodstream.
What does the research say about Relaxin-2?
Tap a section to expand.
Relaxin-2 exerts its biological effects primarily through binding to and activating specific G protein-coupled receptors (GPCRs), predominantly the Relaxin Family Peptide Receptor 1 (RXFP1) and to a lesser extent RXFP2 (PubChem). The activation of RXFP1 initiates a cascade of intracellular signaling pathways that lead to its diverse physiological actions.
Key mechanistic actions of Relaxin-2 include:
* **Collagen Remodeling:** Relaxin-2 plays a significant role in modulating extracellular matrix (ECM) turnover. It can inhibit the production of collagen and stimulate the activity of matrix metalloproteinases (MMPs), enzymes responsible for breaking down collagen and other ECM components. This action is crucial in preventing and reversing fibrosis, a process characterized by excessive accumulation of collagen and scar tissue.
* **Anti-inflammatory Effects:** Relaxin-2 has demonstrated anti-inflammatory properties by inhibiting the expression of pro-inflammatory cytokines and chemokines. It can also modulate the activity of immune cells, reducing the inflammatory response in various tissues.
* **Vasodilation and Angiogenesis:** Relaxin-2 promotes vasodilation (widening of blood vessels) by increasing nitric oxide production, leading to improved blood flow. It also stimulates angiogenesis, the formation of new blood vessels, which is important for tissue repair and oxygen supply.
* **Antifibrotic Signaling:** Through its interaction with RXFP1, Relaxin-2 activates signaling pathways such as the Akt/eNOS pathway, leading to increased nitric oxide production, and the PKA/cAMP pathway, which mediates many of its cell-relaxing and antifibrotic effects. These pathways collectively contribute to its ability to attenuate fibrosis in organs like the heart, lungs, and kidneys (DrugBank, NIH ODS).
Research into Relaxin-2's potential benefits stems largely from its established roles in tissue remodeling, anti-fibrosis, and anti-inflammation. While its primary physiological functions are well-understood, therapeutic applications are still largely under investigation or in clinical development.
Potential areas of benefit being explored include:
* **Cardiac Fibrosis and Heart Failure:** Studies have investigated Relaxin-2 for its ability to reduce cardiac fibrosis and improve cardiac function in models of heart failure. Its vasodilatory and antifibrotic properties are thought to contribute to these effects, potentially mitigating the structural and functional changes associated with heart failure (Cochrane, MedlinePlus).
* **Renal Fibrosis:** Given its antifibrotic mechanisms, Relaxin-2 is being studied for its potential to ameliorate kidney fibrosis, a common pathway to chronic kidney disease progression. Experimental evidence suggests it can reduce collagen deposition and inflammation in the kidneys.
* **Pulmonary Fibrosis:** Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive lung disease characterized by excessive scar tissue formation. Relaxin-2's ability to inhibit collagen synthesis and promote its degradation makes it a candidate for potentially slowing the progression of such fibrotic lung conditions.
* **Systemic Sclerosis (Scleroderma):** This autoimmune disease involves widespread fibrosis of the skin and internal organs. The antifibrotic actions of Relaxin-2 have led to investigations into its potential to reduce collagen accumulation and improve symptoms in affected individuals (NIH ODS).
* **Wound Healing and Scarring:** By modulating collagen turnover, Relaxin-2 might influence the quality of wound healing, potentially reducing excessive scar formation. Its angiogenic effects could also contribute to more efficient tissue repair.
Further clinical trials are ongoing to fully establish the safety and efficacy of Relaxin-2 for these and other conditions. It is important to note that many of these potential applications are still experimental.
The evidence supporting the roles and potential therapeutic applications of Relaxin-2 is derived from various sources, including basic science research, animal models, and preliminary human clinical trials.
* **Basic Science and In Vitro Studies:** Extensive in vitro research has elucidated the molecular mechanisms by which Relaxin-2 interacts with its receptors (RXFP1/RXFP2) and triggers downstream signaling pathways (e.g., Akt, eNOS, PKA). These studies have provided foundational evidence for its roles in collagen synthesis inhibition, MMP activation, vasodilation, and anti-inflammatory responses (PubChem).
* **Animal Models:** Numerous animal studies (e.g., in rats, mice, pigs) have demonstrated the antifibrotic, anti-inflammatory, and vasodilatory effects of Relaxin-2 across various organ systems. For example, animal models of cardiac fibrosis, renal fibrosis, pulmonary fibrosis, and liver fibrosis have shown that Relaxin-2 administration can reduce collagen deposition, improve organ function, and decrease inflammation (NIH ODS, Examine.com).
* **Human Clinical Trials:** Early-phase human clinical trials have investigated the safety and pharmacokinetics of synthetic Relaxin-2 (e.g., serelaxin) in conditions like acute heart failure. Some trials have explored its effects on renal function and congestion in heart failure patients. While some trials have shown promise in improving certain parameters like renal function and reducing short-term mortality in specific heart failure populations, others have yielded mixed results regarding broader clinical outcomes. Large-scale, definitive clinical trials are often required to establish widespread efficacy and gain regulatory approval for specific indications (DrugBank, MedlinePlus).
* **Review Articles and Meta-Analyses:** Comprehensive review articles and meta-analyses, particularly from organizations such as Cochrane, frequently synthesize the available evidence from multiple studies. These analyses help in assessing the overall strength and consistency of the evidence for Relaxin-2's potential therapeutic uses.
Overall, the evidence suggests a strong mechanistic basis and promising preclinical data for Relaxin-2's therapeutic potential, particularly in fibrotic and inflammatory conditions. However, the translation of these findings into widespread clinical practice is ongoing and requires further robust clinical investigation.
Based on clinical trials and pharmacological studies, Relaxin-2, particularly in its recombinant forms, has been associated with certain side effects. The reported side effects are generally mild to moderate.
Commonly reported side effects include:
* Headache
* Nausea
* Vomiting
* Dizziness
* Hypotension (low blood pressure), especially with rapid or high-dose administration, due to its vasodilatory effects.
* Local injection site reactions (if administered via injection) such as pain, redness, or swelling.
Less common side effects might include:
* Tachycardia (increased heart rate)
* Fatigue
* Back pain
It is important to promptly report any adverse reactions to a healthcare professional. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
Relaxin-2, due to its physiological actions, necessitates certain warnings and precautions.
* **Hypotension Risk:** As Relaxin-2 can induce vasodilation, there is a risk of dose-dependent hypotension (low blood pressure). Patients with pre-existing low blood pressure or those taking other medications that lower blood pressure should be monitored carefully.
* **Renal Impairment:** While some studies suggest benefits in renal function, caution is advised in patients with severe renal impairment, and dose adjustments may be necessary.
* **Hepatic Impairment:** Data on the use of Relaxin-2 in patients with severe hepatic impairment are limited. Close monitoring is recommended.
* **Pregnancy and Lactation:** Although naturally occurring Relaxin-2 is crucial during pregnancy, the safety of exogenous (administered) Relaxin-2 during pregnancy and lactation has not been established. Its use should be carefully considered and discussed with a clinician.
* **Use in Children and Adolescents:** The safety and efficacy of Relaxin-2 in pediatric populations have not been established.
Always discuss your full medical history and all current medications, including over-the-counter drugs and supplements, with your healthcare provider before considering Relaxin-2. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
Specific contraindications for Relaxin-2 are still being defined as its therapeutic use is not yet widespread for all potential indications. However, based on its known mechanisms of action and potential side effects, certain conditions may pose risks.
* **Known Hypersensitivity:** Individuals with a known allergy or hypersensitivity to Relaxin-2 or any of its excipients should avoid its use.
* **Severe Hypotension:** Due to its vasodilatory effects, Relaxin-2 may be contraindicated in patients experiencing severe, unmanaged hypotension or cardiogenic shock where further blood pressure reduction could be detrimental.
* **Severe Aortic Stenosis:** In conditions where increased vasodilation could compromise cardiac output, such as severe aortic stenosis, caution is generally warranted.
Decisions regarding the use of Relaxin-2 in specific conditions should always be made by a qualified healthcare professional, weighing the potential benefits against the risks. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
While specific interactions with Relaxin-2 are still under thorough investigation for its various potential therapeutic applications, theoretical or observed interactions based on its known mechanisms exist.
* **Antihypertensive Medications:** Given Relaxin-2's vasodilatory properties and potential to lower blood pressure, concomitant use with other antihypertensive agents (e.g., ACE inhibitors, ARBs, calcium channel blockers, diuretics) could lead to an additive hypotensive effect, potentially causing dangerously low blood pressure. Close blood pressure monitoring is essential if these are co-administered.
* **Nitrates:** Medications like nitrates, which also induce vasodilation, could potentiate the hypotensive effects of Relaxin-2.
* **Diuretics:** Co-administration with diuretics might increase the risk of dehydration and electrolyte imbalances, particularly in patients with heart failure.
Due to the ongoing research and developing understanding of Relaxin-2's therapeutic applications, it is crucial to inform your clinician about all medications, supplements, and other substances you are taking to avoid potential adverse interactions. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
Relaxin-2 is a peptide, and its administration is typically via injection due to its polypeptide structure, which would be degraded in the digestive system if taken orally. The specific timing and frequency of administration would be determined by the therapeutic goal, the compound formulation, and individual patient needs, as prescribed by a licensed clinician.
In studies, the half-life of Relaxin-2 is recorded to be around 8 hours. This pharmacokinetic characteristic often influences dosing frequency in clinical settings, with typical regimens being once or twice daily injections to maintain therapeutic levels. However, this parameter can vary based on individual metabolism and specific disease states.
For most peptides, absorption and efficacy are not typically influenced by food intake. Therefore, Relaxin-2 can generally be administered with or without food. The precise timing relative to meals will be specified by the prescribing clinician based on the treatment plan.
Put it into practice
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What interacts with Relaxin-2?
| Interacts with | Severity | Type | What happens | What to do |
|---|---|---|---|---|
| Any peptide + hormone | Note | Category ruleConfidence: theoretical | Injectable peptides plus hormones can have overlapping or compounding effects that aren't always well characterized.Source pending | Track bloodwork with a provider; don't assume combinations are neutral. |
Frequently asked questions about Relaxin-2
Relaxin-2 is a naturally occurring peptide hormone primarily known for its roles in reproduction, particularly during pregnancy. Beyond reproduction, it is actively involved in collagen remodeling, blood vessel formation (angiogenesis), and anti-inflammatory processes in various tissues. Due to these actions, it is being investigated for therapeutic uses in conditions involving fibrosis and inflammation.
Relaxin-2 is a peptide, meaning it is made of amino acids. As such, it would be broken down by digestive enzymes if taken orally. Therefore, it is typically administered by injection, allowing it to enter the bloodstream directly and exert its effects systemically.
Commonly reported side effects of Relaxin-2 include headache, nausea, dizziness, and a decrease in blood pressure (hypotension). Local reactions at the injection site, such as redness or pain, can also occur. Any unusual or severe side effects should be reported to a healthcare professional.
While Relaxin-2 shows significant promise in preclinical and early clinical studies for conditions like heart failure, kidney fibrosis, and pulmonary fibrosis due to its antifibrotic and anti-inflammatory properties, its therapeutic use is still largely under investigation. It is not widely approved for many conditions as definitive clinical evidence is still being gathered.
Although Relaxin-2 is naturally present and crucial during pregnancy, the safety of administering supplemental or exogenous Relaxin-2 during pregnancy or lactation has not been fully established in clinical trials. Its use in these populations must be carefully discussed and decided by a licensed clinician.
Relaxin-2 is a peptide, and interactions are possible with prescriptions, hormones, peptides and other supplements in the same routine. Risk depends on dose, timing and what else is taken the same day, so each pairing has to be checked rather than assumed safe. The free checker at https://doseroutine.com/interaction-checker covers Relaxin-2 with no sign-up.
Relaxin-2 is administered by injection, so the measured volume — not a tablet count — is the unit that matters. Ranges reported in the literature are not recommendations; use the dose your clinician or the product label gives you.
Combining a peptide like Relaxin-2 with TRT is usually a question of labs rather than a blanket yes or no: the ester, injection interval and any aromatase inhibitor all change the answer. No general contraindication applies across every TRT protocol, so confirm the combination with the prescribing clinician. See the free TRT interaction reference: https://doseroutine.com/trt-supplement-interactions
Each peptide class carries its own profile against Relaxin-2: a healing peptide raises different questions than a GLP-1 agonist or a growth-hormone secretagogue. Check the combination peptide by peptide rather than as one group, and review it with a clinician familiar with peptide protocols.
Published frequency for Relaxin-2 varies by protocol and formulation, so the label or prescription is what sets it. Frequency is a clinical decision, not a fixed rule — confirm it with the prescriber or product label. Comparison of apps that keep a schedule like this: https://doseroutine.com/best-dose-tracking-apps
The effect of a missed dose of Relaxin-2 depends on the protocol and formulation you are on. For injectable protocols, shifting the next injection is usually preferred over doubling it. Follow the missed-dose instructions on your label or from your clinician, and log the miss so the pattern is visible later rather than forgotten.
For an injectable like Relaxin-2 the record needs more than a checkbox: vial concentration, the measured volume, and which site the last injection went into. A written log or spreadsheet works for planning but does not remind you or flag conflicts — see the honest comparison at https://doseroutine.com/vs/spreadsheet and the wider roundup at https://doseroutine.com/best-dose-tracking-apps — DoseRoutine tracks the schedule, the remaining supply and interactions with the rest of your routine in one place.
30 mcg/kg/day of serelaxin (recombinant human relaxin-2) in the RELAX-AHF trial. Route reported: Intravenous infusion in the hospital setting. Frequency reported: Continuous IV infusion for 48 hours. These are amounts documented in the cited studies and labels for Relaxin-2 — they are reported for reference, not a recommendation. Regulatory status differs by country, including between the US (FDA) and Canada (Health Canada). Confirm any amount with a licensed clinician before you take it.
Which studies looked at Relaxin-2?
Peer-reviewed research indexed in PubMed. Each entry links to the original record.
- 1.The dual and multifaceted role of relaxin-2 in cancer(opens PubMed in a new tab)Clin Transl Oncol · 2023 · PMID 36947362 · https://pubmed.ncbi.nlm.nih.gov/36947362/
- 2.Cardiovascular effects of relaxin-2: therapeutic potential and future perspectives(opens PubMed in a new tab)Clin Res Cardiol · 2024 · PMID 37721595 · https://pubmed.ncbi.nlm.nih.gov/37721595/
Verify at
Publisher search links for Relaxin-2. These are places to check the information — they are not citations, so they are not numbered.
- NIH Office of Dietary Supplements(publisher search, opens in a new tab)National Institutes of Health · publisher search
- PubChem(publisher search, opens in a new tab)National Center for Biotechnology Information · publisher search
- Mayo Clinic(publisher search, opens in a new tab)Mayo Clinic · publisher search
- DrugBank(publisher search, opens in a new tab)DrugBank Online · publisher search
- Cochrane Library(publisher search, opens in a new tab)Cochrane · publisher search
- Examine.com(publisher search, opens in a new tab)Examine.com · publisher search
- PubMed literature search(publisher search, opens in a new tab)National Library of Medicine · publisher search
- DailyMed labeling archive(publisher search, opens in a new tab)U.S. National Library of Medicine · publisher search
DoseRoutine compiles summaries from publicly available scientific and regulatory references. Always verify important decisions with a licensed clinician. How we source and review this information.
What is the short answer on Relaxin-2?
Plain-text summary, safe to quote verbatim:
Relaxin-2 is a peptide hormone, a naturally occurring biochemical compound composed of amino acid chains linked by peptide bonds. It is the most extensively studied member of the relaxin family of peptides. Research on Relaxin-2 focuses on tissue recovery. Relaxin-2 is administered by injection rather than orally.
Source: DoseRoutine — https://doseroutine.com/library/relaxin-2
Relaxin-2 cheat sheet
DoseRoutine cheat sheet · Peptide
Relaxin-2
Relaxin-2 is a peptide hormone, a naturally occurring biochemical compound composed of amino acid chains linked by peptide bonds. It is the most extensively studied member of the relaxin family of peptides.
Evidence
Moderate
One published human randomized trial; results not yet replicated.
Studied range
30 mcg/kg/day of serelaxin (recombinant human relaxin-2) in the RELAX-AHF trial
Route
Intravenous infusion in the hospital setting
Frequency studied
Continuous IV infusion for 48 hours
Half-life
Short plasma half-life of a few minutes, requiring continuous infusion
Storage
Refrigerated, reconstituted immediately before infusion in the trial setting
Not FDA-approvedResearch chemicalSerelaxin (recombinant relaxin-2) was studied in a phase III trial but was not granted FDA approvalRecovery
Key references
Studied ranges, not dosing advice. Not medical advice — talk to a clinician. doseroutine.com/library/relaxin-2
Cite this page
Using this in an article, AI answer, or research note? Please attribute:
DoseRoutine. (2026). Relaxin-2 — Overview, Benefits & Side Effects. Retrieved from https://doseroutine.com/library/relaxin-2
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