Relaxin-2 (Serelaxin) dosing & administration
Recombinant human relaxin-2 studied for acute heart failure recovery and cardiovascular support
Written by Michael Carroll — Owner, Director of Research · Reviewed by the Peptide Initiative Research Team · Editorial standards
Dosing
How much do I take?
Intravenous: Delivered straight into a vein through a drip (IV), done by a clinician.
Bioavailability Complete (about 100%) — delivered straight into the bloodstream.
Timing
Best time to take
Administer at a consistent time each day. Consistency matters more than the specific time of day.
With food?
Food timing does not significantly affect absorption for injectable peptides.
If stacking
If combining Relaxin-2 (Serelaxin) with other peptides, space administrations by 15-30 minutes. Consult your healthcare provider before combining with prescription medications.
Adjusting your dose
Increase if
- Current dose is well-tolerated for 2+ weeks
- Desired effects not yet noticeable
- Healthcare provider recommends dose increase
Decrease if
- Side effects become bothersome or persistent
- Desired effects achieved at lower dose
- Healthcare provider recommends reduction
Signs of right dose
- Noticeable improvement in target symptoms
- Good tolerance with minimal side effects
- Consistent positive response between doses
Administration
How do I use it?
Reconstitution
What you need
Injection
Route
Topical application (no injection required)
Best sites
Storage
Before reconstitution
Refrigerate at 36-46°F (2-8°C).
After reconstitution
Refrigerate and use within 30 days.
Signs of degradation — discard the vial
Sample daily schedule
Morning (or as directed)
1-10 mcg injection
Site: As directed
Administer once daily. Maintain consistency for optimal results.
Safety
Is it safe?
Side effects
Commonly reported: Hypotension (low blood pressure) - most common, Tachycardia (increased heart rate), Headache, Nausea, Dizziness, Peripheral edema (swelling), Increased creatinine levels, Hyperkalemia (high potassium), Syncope (fainting), Atrial fibrillation, Blood pressure checks every 2-4 hours during infusion, Kidney function (creatinine and eGFR), Electrolytes, particularly potassium, Heart rate and cardiac rhythm, Urine output
Stop and seek help if
- Severe allergic reaction—difficulty breathing, significant swelling, or anaphylaxis
- Persistent or worsening side effects that don't resolve with dose adjustment
- Your healthcare provider recommends discontinuation
- Pregnancy or planned pregnancy
- Achievement of treatment goals (discuss maintenance protocol with provider)
Relaxin-2 (Serelaxin) should only be used under the guidance of a qualified healthcare provider. This information is for educational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting, adjusting, or stopping any peptide protocol.
Flagged pairings
- Other IV vasodilators — Other IV vasodilators (may cause excessive hypotension)
- Strong ACE inhibitors without dose adjustment — Strong ACE inhibitors without dose adjustment
Published research
What the studies show
Voors AA, et al. · 2025
This study investigated Relaxin-2 (Serelaxin), contributing to our understanding of its mechanism and therapeutic potential.
Martins RC, et al. · 2020
This study investigated Relaxin-2 (Serelaxin), contributing to our understanding of its mechanism and therapeutic potential.
Metra M, et al. · 2019
This study investigated Relaxin-2 (Serelaxin), contributing to our understanding of its mechanism and therapeutic potential.
Maggioni AP, et al. · 2019
This study investigated Relaxin-2 (Serelaxin), contributing to our understanding of its mechanism and therapeutic potential.
Teerlink JR, Cotter G, Davison BA, et al. · 2013
Ponikowski P, Mitrovic V, Ruda M, et al. · 2014
Invasive haemodynamic study in 71 acute heart failure patients: serelaxin 30 ug/kg/day produced a significantly greater fall in peak pulmonary capillary wedge pressure than placebo (-2.44 mmHg, P = 0.004) and reduced pulmonary artery pressure, right atrial pressure, systemic and pulmonary vascular resistance, and systolic/diastolic blood pressure.
Bathgate RAD, Halls ML, van der Westhuizen ET, Callander GE, Kocan M, Summers RJ · 2013
Relaxin acts as a vasodilator and cardiac stimulant and as an antifibrotic agent; relaxin and INSL3 are the cognate ligands for the G protein-coupled receptors RXFP1 and RXFP2, with RXFP1 activating a wide spectrum of signalling pathways generating second messengers including cAMP and nitric oxide.
Conrad KP · 2011
Relaxin is a 6 kDa corpus luteal hormone circulating during pregnancy; its administration induces systemic and renal vasodilation, acting through PI3K/Akt-dependent activation of endothelial nitric oxide synthase and, over the longer term, vascular endothelial and placental growth factors and arterial gelatinase activity.
Teerlink JR, Davison BA, Cotter G, et al. · 2020
Fixed-effect meta-analysis of six randomised trials (6105 serelaxin, 5254 control): worsening heart failure to day 5 fell from 8.1% to 6.0% (HR 0.77), renal function markers, NT-proBNP and troponin improved, no significant adverse outcomes were noted, and all-cause mortality was reduced (HR 0.87).
Dahlke M, Ng D, Yamaguchi M, et al. · 2015
Double-blind dose-ranging study of 48-hour intravenous serelaxin infusions in healthy subjects: serelaxin was well tolerated at all doses, serum sodium, potassium, chloride, urea, creatinine and haematocrit were followed as pharmacodynamic measures, and estimated glomerular filtration rate rose significantly versus placebo.
Novartis Pharmaceuticals / ClinicalTrials.gov · 2019
Posted adverse-event tables for 3257 serelaxin and 3248 placebo recipients record hypotension (69 non-serious, 14 serious), headache (74), nausea (59), dizziness (27 non-serious, 1 serious), atrial fibrillation (46 non-serious, 10 serious), blood creatinine increased (36), hyperkalaemia (40), syncope (5 serious), tachycardia and ventricular tachycardia, acute kidney injury (35) and renal failure (42) in the serelaxin arm.
Novartis Pharmaceuticals / ClinicalTrials.gov · 2017
Repeat 48-hour intravenous serelaxin infusions over 16 weeks in chronic heart failure: 0.50% of serelaxin recipients developed anti-serelaxin antibodies at any time versus 0.00% on placebo, with per-interval rates of 0.48-0.49% after each single infusion.
Novartis · 2017
Media release of 22 March 2017: RELAX-AHF-2 did not meet its primary endpoints of reduction in cardiovascular death through Day 180 or reduced worsening heart failure through Day five.
Novartis Europharm Ltd / European Medicines Agency · 2017
Novartis notified the EMA that development of serelaxin (Reasanz) for the treatment of acute heart failure has been discontinued for possible lack of efficacy in adults, following the results of the global Phase III RELAX-AHF-2 study; no new safety concerns associated with serelaxin were observed.
Wolowiec L, Jasniak A, Osiak-Gwiazdowska J, et al. · 2025
Review of relaxin therapeutics: serelaxin was developed by Novartis/Corthera and produced through recombinant expression in E. coli, has a short half-life of approximately 2 hours, is given by the intravenous route reflecting its typical use in hospital settings, and acts by binding RXFP1 in cardiovascular tissues to stimulate cAMP, ERK and NO/cGMP pathways.
Gao XM, Su Y, Moore S, et al. · 2019
In mice after cardiac ischaemia-reperfusion, relaxin reduced microvascular obstruction and leakage and endothelial monolayer permeability, and at two weeks echocardiography showed preserved contractile function and limited chamber dilatation versus untreated controls, indicating alleviated adverse cardiac remodelling.
Snowdon VK, Lachlan NJ, Hoy AM, et al. · 2017
Serelaxin binds RXFP1 and increases renal perfusion in healthy human volunteers; in rat models it raised kidney perfusion, oxygenation and function via reduced renal vascular resistance and AKT/eNOS/NO activation, and a 120-minute infusion in cirrhotic patients raised total renal arterial blood flow by 65% without detrimental effect on systemic blood pressure.
Head to head
Relaxin-2 (Serelaxin) compared
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The complete Relaxin-2 (Serelaxin) research profile: mechanism of action, clinical studies, effectiveness timeline, and FAQ.