peptideNot FDA-approvedResearch chemicalNever approved by the FDA or EMA; the RELAX-AHF-2 trial did not meet its primary endpoints and clinical development for acute heart failure was discontinuedOnly ever administered as an investigational hospital infusion in trials, never sold as a retail product
SerelaxinBenefits, Dosage & Interactions
Serelaxin is a recombinant form of human relaxin-2, a naturally occurring peptide hormone structurally related to insulin. Research on Serelaxin focuses on tissue recovery. Serelaxin is administered by injection rather than orally. Dose, response, and interaction risk vary by individual, so use should be reviewed with a clinician.
How much Serelaxin do people take?
The pivotal RELAX-AHF-2 trial used a fixed 30 µg/kg/hour continuous infusion. Route reported: Intravenous infusion in every published trial. Frequency reported: Continuous infusion for up to 48 hours. These are amounts documented in the cited studies and labels for Serelaxin — 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: Strong — 1 human randomized trial published.
Evidence strengthStrong · 4/4
PreclinicalStrong human evidence
1 human randomized trial published.
Plasma half-life
Approximately 10 minutes (recombinant human relaxin-2)
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
- The pivotal RELAX-AHF-2 trial used a fixed 30 µg/kg/hour continuous infusion[1]
- Route studied
- Intravenous infusion in every published trial[1]
- Frequency
- Continuous infusion for up to 48 hours[1]
- Cycle length
- Single hospitalization episode (up to 48 hours) in the trials[1]
- Half-life
- Approximately 10 minutes (recombinant human relaxin-2)[1]
- Storage
- Refrigerated lyophilized vial, reconstituted immediately before infusion in hospital[1]
Reported for Serelaxin in the cited sources. Published ranges are not dosing advice.
Mixing Serelaxin: 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, Serelaxin 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 Serelaxin entry is written from. Each number matches an inline marker above.
- [1]Effects of Serelaxin in Patients with Acute Heart FailureMetra M, Teerlink JR, Cotter G, et al. · The New England Journal of Medicine · 2019 · Peer-reviewed · PMID 31433919
- [2]Effects of serelaxin in patients admitted for acute heart failure: a meta-analysisTeerlink JR, Davison BA, Cotter G, et al. · European Journal of Heart Failure · 2020 · Peer-reviewed · PMID 31886953
References & Evidence
Sources on this page that document Serelaxin dosing, timing and safety.
- [1]National Center for Biotechnology Information View source
Educational information only — not medical advice. Dose ranges vary by person, indication and prescriber.
What is Serelaxin studied for?
What is Serelaxin?Sources for this section: Jumps to this entry in the sources and references list at the end of the page.
Serelaxin is a recombinant form of human relaxin-2, a naturally occurring peptide hormone structurally related to insulin. In humans, relaxin-2 is primarily known for its roles in the female reproductive system, particularly during pregnancy and childbirth, where it mediates connective tissue remodeling and vasodilation. Serelaxin was developed as an investigational drug for the treatment of acute heart failure (AHF). Its physiological effects include vasodilation, anti-fibrotic activity, and anti-inflammatory properties. These actions are mediated through its interaction with relaxin family peptide receptor 1 (RXFP1), primarily found in the heart, kidneys, and blood vessels. The peptide's half-life in the human body is approximately 8 hours, requiring continuous intravenous administration in clinical studies (DrugBank, PubChem).
What does the research say about Serelaxin?
Tap a section to expand.
Serelaxin exerts its pharmacological effects through the activation of relaxin family peptide receptor 1 (RXFP1). This receptor is a G protein-coupled receptor (GPCR) that, upon activation, can trigger various intracellular signaling pathways. In the cardiovascular system, RXFP1 activation by serelaxin leads to a cascade of events that promote vasodilation. This involves increased production of nitric oxide (NO) and prostacyclin, both potent vasodilators, in endothelial cells. The resultant relaxation of blood vessels, particularly in the systemic and renal circulations, contributes to reduced preload and afterload on the heart, which is beneficial in conditions like acute heart failure. Beyond its direct vasodilatory effects, serelaxin also demonstrates anti-fibrotic and anti-inflammatory properties. These actions may involve modulating collagen synthesis and turnover, as well as inhibiting certain inflammatory pathways, potentially contributing to myocardial protection and remodeling. These mechanisms collectively aim to improve hemodynamic function and organ perfusion in acute cardiovascular stress (DrugBank, PubChem).
Source for this section: Sources for How does Serelaxin work?: Jumps to this entry in the sources and references list at the end of the page.
Clinical research has primarily investigated serelaxin for its potential benefits in acute heart failure (AHF). Studies have explored its ability to:
* **Improve symptoms of dyspnea:** Some early trials indicated that serelaxin might alleviate shortness of breath in patients experiencing acute heart failure, as measured by patient-reported breathing ease (Cochrane, ClinicalTrials.gov reports).
* **Reduce organ congestion:** Its vasodilatory and diuretic effects were hypothesized to lessen congestion in various organs, including the lungs and kidneys, which are commonly affected in AHF (Cochrane).
* **Improve renal function:** By promoting renal vasodilation, serelaxin was thought to improve kidney perfusion and potentially mitigate renal dysfunction often associated with acute heart failure (Cochrane).
* **Decrease cardiovascular mortality:** While initial studies showed promise in some endpoints, larger trials were conducted to assess its impact on major cardiovascular events and mortality, though these did not consistently meet primary endpoints (Cochrane, EMA rejection reports).
It is important to note that while some early-phase studies showed potential, larger and more definitive trials did not consistently demonstrate significant clinical benefits in reducing cardiovascular mortality or rehospitalization rates in acute heart failure. Consequently, serelaxin has not received regulatory approval for this indication (EMA SmPC, FDA review documents).
The evidence supporting the use of serelaxin for acute heart failure comes primarily from several large-scale clinical trials. The RELAX-AHF (Relaxin in Acute Heart Failure) program was a key part of its development.
Early phase 2 trials suggested that serelaxin could improve symptoms like dyspnea and might have beneficial effects on cardiovascular and renal outcomes in patients with acute heart failure. These promising results led to larger phase 3 trials.
The RELAX-AHF-2 study, a pivotal phase 3 trial, aimed to confirm these benefits. This randomized, double-blind, placebo-controlled study enrolled a large number of patients with acute heart failure. The primary endpoints were cardiovascular death or worsening heart failure by day 180, and cardiovascular death by day 180. The findings of RELAX-AHF-2 did not demonstrate a statistically significant reduction in either of these primary endpoints. While serelaxin was generally well-tolerated, the study did not meet its primary efficacy goals (Cochrane Review, ClinicalTrials.gov NCT01870766).
Another review by Cochrane evaluating various therapies for acute heart failure noted that while serelaxin showed some early promise in symptom relief, the larger trials did not provide conclusive evidence for hard clinical outcomes such as mortality or rehospitalization. Regulatory bodies, including the European Medicines Agency (EMA) and the U.S. Food and Drug Administration (FDA), reviewed the extensive clinical data. Due to the lack of consistent and significant benefit on major clinical endpoints, serelaxin did not receive marketing authorization for acute heart failure (EMA SmPC rejection documents, FDA review documents).
Clinical trials of serelaxin for acute heart failure have reported various side effects. These are generally mild to moderate in severity. Common side effects observed included:
* Headache
* Nausea
* Hypotension (low blood pressure), which is consistent with its vasodilatory properties
* Tachycardia (increased heart rate)
* Dizziness
* Flushing
More serious but less common side effects reported during clinical investigations included worsening heart failure or renal dysfunction, although these were not consistently attributed solely to serelaxin. The overall safety profile was considered acceptable, but the lack of significant efficacy limited its development. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
Individuals with certain pre-existing conditions or those on specific medications may need to exercise caution with serelaxin.
* **Hypotension:** Due to its vasodilatory effects, serelaxin can lower blood pressure. Patients who already have low blood pressure or are on medications that lower blood pressure should be monitored carefully.
* **Renal Impairment:** While studies explored potential renal benefits, careful monitoring of kidney function is advised due to the complex interplay between cardiovascular and renal systems in acute heart failure.
* **Pregnancy and Lactation:** As a recombinant human relaxin, its effects on pregnancy and lactation are not fully established in a therapeutic context for acute heart failure. Given relaxin's natural role in pregnancy, caution would be warranted.
Clinical trials have generally indicated that serelaxin was well-tolerated for short-term use in acute settings. However, as it did not receive regulatory approval, broader long-term safety data in diverse populations are not available. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
Specific contraindications for serelaxin have not been established through regulatory approval processes, as the drug did not obtain marketing authorization. However, based on its pharmacological profile and observed side effects in clinical trials, potential relative contraindications or situations where caution would be strongly advised include:
* **Severe Hypotension:** Patients experiencing severe or uncontrolled low blood pressure, as serelaxin's vasodilatory effects could exacerbate this condition.
* **Cardiogenic Shock:** In conditions of profound circulatory collapse, the acute administration of a vasodilator might be detrimental.
* **Known Hypersensitivity:** Any individual with a known allergy or severe reaction to relaxin or any components of the serelaxin formulation.
Without regulatory approval, a comprehensive list of contraindications, warnings, and precautions is not fully delineated as it would be for an approved medication. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
Given that serelaxin did not receive regulatory approval and is not commercially available, definitive drug-drug interaction studies with a broad range of medications are not extensively documented in public regulatory databases. However, based on its known vasodilatory mechanism, potential interactions could include:
* **Other Vasodilators:** Concomitant use with other medications that lower blood pressure (e.g., nitrates, ACE inhibitors, ARBs, phosphodiesterase-5 inhibitors) could lead to an additive hypotensive effect, potentially resulting in symptomatic low blood pressure.
* **Diuretics:** While serelaxin was studied alongside diuretics in acute heart failure, close monitoring would be necessary to avoid excessive fluid loss or electrolyte imbalances, given its potential to influence renal function.
As with any investigational agent, clinical judgment and careful monitoring for adverse effects and interactions would be paramount if serelaxin were to be used in a research setting. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
Serelaxin was administered intravenously in clinical trials, typically as a continuous infusion. The duration of infusion varied depending on the study protocol, often lasting for 24 to 48 hours for patients hospitalized with acute heart failure. Its half-life of approximately 8 hours necessitates continuous administration to maintain therapeutic levels. The timing of administration was generally initiated upon presentation of acute heart failure symptoms, as early intervention was hypothesized to be most beneficial. The formulation was designed for hospital-based use, given the need for intravenous access and continuous monitoring. Specific timing relative to meals (food rule: either) was not a critical factor, given its intravenous route of administration and the acute clinical setting (DrugBank, ClinicalTrials.gov reports).
Source for this section: Sources for When should you take Serelaxin?: Jumps to this entry in the sources and references list at the end of the page.
Put it into practice
Reading about Serelaxin is the first step — DoseRoutine helps you act on it. These free tools turn what you just learned into a routine.
What interacts with Serelaxin?
| 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 Serelaxin
Serelaxin was primarily investigated as a treatment for acute heart failure (AHF) with the aim of improving symptoms like shortness of breath and reducing adverse cardiovascular outcomes. However, it did not receive regulatory approval for this indication.
No, serelaxin has not received regulatory approval from major agencies like the FDA or EMA for any medical indication due to a lack of consistent and significant benefit in pivotal phase 3 clinical trials.
In clinical trials, serelaxin was administered as a continuous intravenous infusion, typically for 24 to 48 hours, in patients hospitalized with acute heart failure.
Common side effects observed in clinical studies included headache, nausea, hypotension (low blood pressure), tachycardia (increased heart rate), dizziness, and flushing. These were generally mild to moderate.
While it was studied alongside standard acute heart failure therapies, caution regarding additive hypotensive effects should be considered if combined with other blood pressure-lowering medications. However, as it's not approved, specific interaction guidelines are not available.
As a peptide, Serelaxin can overlap with other supplements, prescription medicines, hormones and peptides. 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 Serelaxin with no sign-up.
Serelaxin is administered by injection, so the measured volume — not a tablet count — is the unit that matters. Amounts for this peptide vary by protocol, formulation and individual response, so follow the dose your clinician or the product label specifies.
Whether Serelaxin fits alongside testosterone replacement therapy depends on the protocol — dose, ester and ancillaries such as HCG or anastrozole — and on current bloodwork. 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
"Peptides" is not one category — healing peptides, GLP-1 agonists, growth-hormone secretagogues and melanocortins each behave differently next to Serelaxin. Check the combination peptide by peptide rather than as one group, and review it with a clinician familiar with peptide protocols.
Published frequency for Serelaxin 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 Serelaxin 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 Serelaxin 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.
The pivotal RELAX-AHF-2 trial used a fixed 30 µg/kg/hour continuous infusion. Route reported: Intravenous infusion in every published trial. Frequency reported: Continuous infusion for up to 48 hours. These are amounts documented in the cited studies and labels for Serelaxin — 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 Serelaxin?
Peer-reviewed research indexed in PubMed. Each entry links to the original record.
- 1.Effects of Serelaxin in Patients with Acute Heart Failure(opens PubMed in a new tab)N Engl J Med · 2019 · PMID 31433919 · https://pubmed.ncbi.nlm.nih.gov/31433919/
- 2.Serelaxin and acute heart failure(opens PubMed in a new tab)Heart · 2016 · PMID 26603680 · https://pubmed.ncbi.nlm.nih.gov/26603680/
- 3.Serelaxin in acute heart failure: Most recent update on clinical and preclinical evidence(opens PubMed in a new tab)Cardiovasc Ther · 2017 · PMID 27727514 · https://pubmed.ncbi.nlm.nih.gov/27727514/
- 4.Effects of serelaxin in patients admitted for acute heart failure: a meta-analysis(opens PubMed in a new tab)Eur J Heart Fail · 2020 · PMID 31886953 · https://pubmed.ncbi.nlm.nih.gov/31886953/
Sources cited on this page
Specific documents referenced by the numbered markers above. Each number matches the marker in the text.
- PubChem CID 71300755(opens in a new tab)National Center for Biotechnology Information · pubchem.ncbi.nlm.nih.gov/compound/71300755
Verify at
Publisher search links for Serelaxin. These are places to check the information — they are not citations, so they are not numbered.
- Cochrane Library(publisher search, opens in a new tab)Cochrane · publisher search
- ClinicalTrials.gov(publisher search, opens in a new tab)U.S. National Library of Medicine · publisher search
- DrugBank(publisher search, opens in a new tab)DrugBank Online · publisher search
- European Medicines Agency(publisher search, opens in a new tab)European Medicines Agency · publisher search
- FDA-approved labeling (DailyMed)(publisher search, opens in a new tab)U.S. Food and Drug Administration · publisher search
- PubMed literature search(publisher search, opens in a new tab)National Library of Medicine · publisher search
- Wikipedia entry(publisher search, opens in a new tab)Wikipedia · 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 Serelaxin?
Plain-text summary, safe to quote verbatim:
Serelaxin is a recombinant form of human relaxin-2, a naturally occurring peptide hormone structurally related to insulin. Research on Serelaxin focuses on tissue recovery. Serelaxin is administered by injection rather than orally. Dose, response, and interaction risk vary by individual, so use should be reviewed with a clinician.
Source: DoseRoutine — https://doseroutine.com/library/serelaxin
Serelaxin cheat sheet
DoseRoutine cheat sheet · Peptide
Serelaxin
Serelaxin is a recombinant form of human relaxin-2, a naturally occurring peptide hormone structurally related to insulin.
Evidence
Strong
1 human randomized trial published.
Studied range
The pivotal RELAX-AHF-2 trial used a fixed 30 µg/kg/hour continuous infusion
Route
Intravenous infusion in every published trial
Frequency studied
Continuous infusion for up to 48 hours
Half-life
Approximately 10 minutes (recombinant human relaxin-2)
Storage
Refrigerated lyophilized vial, reconstituted immediately before infusion in hospital
Not FDA-approvedResearch chemicalNever approved by the FDA or EMA; the RELAX-AHF-2 trial did not meet its primary endpoints and clinical development for acute heart failure was discontinuedOnly ever administered as an investigational hospital infusion in trials, never sold as a retail productRecovery
Studied ranges, not dosing advice. Not medical advice — talk to a clinician. doseroutine.com/library/serelaxin
Cite this page
Using this in an article, AI answer, or research note? Please attribute:
DoseRoutine. (2026). Serelaxin — Overview, Benefits & Side Effects. Retrieved from https://doseroutine.com/library/serelaxin
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