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Healing & Recovery Protocol

Relaxin-2 (Serelaxin)Complete Dosing & Administration Guide

Recombinant human relaxin-2 studied for acute heart failure recovery and cardiovascular support

Dose Range

1-10mcg

Frequency

Once daily

Route

Intravenous (IV) infusion

Cycle Length

8-12 weeks

Dosing

How much
do I take?

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

Dosing Calculator

Calculate Your Exact Dose

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Step 1: Peptide Weight

Find the weight printed on your peptide vial label

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Peptide vial
5mg

Select Weight

mg

Look for a number followed by 'mg' on the vial label (e.g., 5mg, 10mg)

Administration

How do I
use it?

Reconstitution

What you need

  • Bacteriostatic water
  • Insulin syringes
  • Alcohol swabs

Example

Follow standard reconstitution procedures for peptide preparations.

Calculate dose based on reconstitution volume and desired dose.

Injection

Route

Topical application (no injection required)

Best sites

  • Apply to clean, dry skin on target area

Technique

  • 1.Apply thin layer to clean skin
  • 2.Follow product-specific instructions

Storage

Before reconstitution

Refrigerate at 36-46°F (2-8°C).

After reconstitution

Refrigerate and use within 30 days.

Signs of degradation

  • Cloudy solution
  • Discoloration
  • Particles visible

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?

Safety Profile

Serelaxin (recombinant relaxin-2) completed Phase III heart failure trials with favorable safety profile and cardiovascular benefit signals. Hypotension occurs in 20-25% of subjects requiring hemodynamic monitoring; no serious adverse events directly attributable to serelaxin beyond expected vasodilatory effects. Flushing and headaches mild and transient. No serious immunogenicity despite being recombinant human peptide; repeat dosing shows consistent response.

RELAX-AHF Phase III trial (n=1200) demonstrates serelaxin mechanism through vasodilation measured via invasive hemodynamics with pulmonary capillary wedge pressure reductions (20-30% decreases). Cardiac remodeling prevention shown via echocardiographic left ventricular diameter measurements. Safety data from >1200 patients shows 1-day mortality reduction of 37% in intention-to-treat analysis; no serious immunological reactions despite recombinant origin.

Common Side Effects

Experienced by some users

Hypotension (low blood pressure) - most common

Vasodilation induced by relaxin-2 activation of RXFP1/RXFP2 receptors on vascular endothelium predictably reduces systemic vascular resistance and blood pressure. This is dose-dependent and most pronounced in the first 24 hours of IV infusion, with systolic BP typically dropping 10-20 mmHg.

Management: Establish baseline blood pressure before infusion. Monitor BP every 2-4 hours during the 48-hour infusion and for 2 hours post-infusion. Position patient semi-recumbent or upright to promote venous return. If systolic BP falls below 90 mmHg, reduce infusion rate by 50% or pause infusion and notify physician. Ensure adequate hydration. Have vasopressor agents (norepinephrine, dopamine) immediately available in ICU setting.

Tachycardia (increased heart rate)

Compensatory tachycardia occurs as the heart responds to vasodilation and reduced peripheral resistance. Heart rate typically increases 5-15 bpm and reflects normal baroreceptor reflex activation, though some patients experience reflex tachycardia exceeding 100 bpm.

Management: Monitor heart rate continuously during infusion. Document baseline and post-infusion rates. Tachycardia typically resolves as blood pressure stabilizes. If heart rate exceeds 120 bpm or patient reports palpitations, notify physician—may indicate arrhythmia or inadequate pain control. Ensure adequate hydration and avoid sudden position changes.

Headache

Cerebral vasodilation from relaxin's endothelial effects combined with hemodynamic changes can trigger or exacerbate headaches. Occurs in approximately 5-10% of infusion recipients, typically mild to moderate severity.

Management: Administer acetaminophen (500-1000mg) or NSAIDs if not contraindicated for AHF patients. Ensure dark, quiet environment. Apply cool compresses to temples. Assess BP—hypotension-induced headaches resolve when BP normalizes. Maintain hydration. If severe or accompanied by neurological signs, notify physician immediately.

Nausea

Nausea can result from acute hemodynamic changes, IV administration discomfort, or medication interactions. Generally mild and transient, occurring during initial hours of infusion.

Management: Premedicate with ondansetron (4-8mg IV) or metoclopramide (10mg IV) if nausea anticipated. Avoid food 1-2 hours before and during infusion. Maintain NPO status per institutional protocol. Monitor hydration status. Most nausea resolves within first 12 hours. If severe or associated with vomiting, notify physician and consider alternative antiemetics.

Dizziness

Dizziness or lightheadedness results from acute blood pressure reduction and changes in cerebral perfusion. Risk increases with rapid infusion rate or inadequate hydration. More common in elderly or volume-depleted patients.

Management: Maintain semi-recumbent position to enhance cerebral perfusion. Move slowly when changing positions. Ensure adequate hydration per heart failure protocol. Monitor orthostatic vital signs (supine, sitting, standing if applicable). Reduce infusion rate if dizziness severe. Assess for concurrent medication effects (narcotics, sedatives). Notify physician if accompanied by syncope risk.

Peripheral edema (swelling)

Relaxin-mediated vascular permeability increases and sodium/fluid retention in acute HF can cause or exacerbate peripheral edema, particularly in dependent areas (ankles, sacrum in bed-bound patients). May reflect improved hemodynamics allowing better renal perfusion and fluid redistribution.

Management: Monitor daily weights pre- and post-infusion. Assess pedal edema severity and location. Elevate lower extremities above heart when resting. Apply compression stockings if ordered. Diuretic regimen continuation per cardiology. Check for signs of cellulitis or skin breakdown from chronic edema. Notify physician if edema worsens despite appropriate diuresis.

Increased creatinine levels

Serum creatinine may transiently rise during infusion due to reduced renal perfusion pressure from hypotension or intrinsic glomerular effects. Typically reversible post-infusion as hemodynamics normalize. Can reflect acute tubular necrosis risk in pre-existing renal disease.

Management: Draw baseline creatinine and BUN before infusion start. Repeat every 12-24 hours during 48-hour infusion and at 24-48 hours post-infusion. Calculate eGFR to assess glomerular filtration rate trend. If creatinine increases >0.5 mg/dL or doubling from baseline, reduce infusion rate or pause and notify physician. Ensure adequate hydration. Monitor urine output for oliguria. Hold ACE-I/ARB per institutional protocol during infusion.

Hyperkalemia (high potassium)

Acute kidney injury risk and potential aldosterone suppression from improved renal hemodynamics can elevate serum potassium. Risk increases in patients with baseline renal impairment (eGFR <30) or on ACE-I/ARB therapy.

Management: Draw baseline potassium before infusion. Repeat every 12-24 hours during infusion and post-infusion per protocol. If K+ exceeds 5.5 mEq/L, notify physician immediately. Restrict potassium intake during hospitalization. Hold potassium supplements and potassium-sparing agents. Have calcium gluconate, insulin/glucose, and emergency kayexalate available. Perform EKG if K+ elevated to assess for peaked T-waves or other cardiac changes.

Syncope (fainting)

Profound hypotension combined with positive chronotropic effects can precipitate vasovagal syncope or hypotensive episodes, particularly with sudden position changes or straining. Risk highest in first 24 hours of infusion.

Management: Maintain patient on continuous cardiac telemetry. Institute fall precautions—bed in low position, side rails up, call bell within reach. Assist with all position changes and ambulation. If syncope occurs, immediately lay patient flat, elevate legs, reduce/pause infusion, and notify physician. Assess for injuries from fall. May require vasopressor support or infusion rate reduction. Hold patient in ICU setting post-syncope.

Atrial fibrillation

Acute hemodynamic changes, atrial dilation from HF, or catecholamine surges can trigger atrial fibrillation de novo or exacerbate pre-existing AF. Occurs in 2-5% of infusion recipients, particularly those with structural heart disease or elevated filling pressures.

Management: Maintain continuous cardiac telemetry throughout infusion. Obtain baseline 12-lead EKG before infusion. If AF develops, notify physician immediately. Do not delay intervention. Prepare for possible rate control (beta-blockers, calcium channel blockers) or rhythm control strategies per cardiology. Ensure adequate anticoagulation if not already on anticoagulant. Monitor for hemodynamic deterioration with rapid ventricular response. Have emergency equipment available.

Blood pressure checks every 2-4 hours during infusion

Continuous hemodynamic monitoring is essential to assess the critical vasodilatory effects of relaxin-2 and catch hypotension early. Invasive (arterial line) or non-invasive BP monitoring every 1-4 hours captures BP trend and infusion tolerance.

Management: Establish continuous non-invasive BP monitoring (automatic cuff every 2-4 hours minimum) or invasive arterial line for closer monitoring. Position BP cuff at heart level for accuracy. Document systolic, diastolic, and mean arterial pressures. Plot trend on chart to visualize hemodynamic response. If MAP drops below 65 mmHg or SBP below 90 mmHg, reduce infusion rate by 50%, notify physician, and reassess in 15-30 minutes before restarting.

Kidney function (creatinine and eGFR)

Acute kidney function assessment is critical because hypotension and intrinsic renal effects from relaxin can precipitate acute kidney injury. Baseline renal function predicts risk—patients with eGFR <30 are at higher risk for worsening function.

Management: Draw baseline serum creatinine, BUN, and calculate eGFR before infusion. Repeat creatinine every 12-24 hours during 48-hour infusion. Monitor 24-hour urine creatinine and urine electrolytes per protocol. Assess urine output hourly (target >0.5 mL/kg/hr). If creatinine rises >0.5 mg/dL acutely, reduce infusion rate and ensure adequate hydration. Hold nephrotoxic agents. Consider contrast avoidance for any imaging during treatment window.

Electrolytes, particularly potassium

Acute shifts in serum electrolytes (sodium, potassium, magnesium) occur from hemodynamic changes, diuretic therapy, and altered renal handling. Hyponatremia and hyperkalemia represent the primary electrolyte concerns during relaxin infusion.

Management: Draw baseline comprehensive metabolic panel (CMP) before infusion including Na+, K+, Mg2+, Cl-. Repeat CMP every 12-24 hours during infusion per institutional protocol. Monitor and restrict sodium intake during HF hospitalization (typically <2g daily). Supplement potassium only if serum K+ <3.5 mEq/L. Monitor for hyponatremia symptoms (confusion, altered mental status, seizures). If electrolyte abnormality detected, notify physician and adjust supplementation accordingly.

Heart rate and cardiac rhythm

Continuous cardiac monitoring captures the heart rate response to hemodynamic changes and detects arrhythmias. Telemetry surveillance is mandatory during 48-hour infusion given the potent hemodynamic effects of relaxin.

Management: Initiate continuous cardiac telemetry before infusion starts. Monitor QRS rate, rhythm, PR interval, and QT interval. Obtain baseline 12-lead EKG before infusion. Watch for new arrhythmias including AF, PACs, PVCs, or conduction abnormalities. If significant arrhythmia develops (sustained VT, bradycardia <50, AF with RVR >120), immediately notify physician and be prepared for intervention. Continue telemetry for 2+ hours post-infusion.

Urine output

Diuresis or oliguria responses to relaxin infusion depend on baseline renal function and hemodynamics. Expected response is improved urine output (>1-1.5 L/24hr in most) as renal perfusion improves. Oliguria (<400-500 mL/24hr) signals acute kidney injury.

Management: Insert Foley catheter and monitor urine output hourly during infusion. Document color, clarity, and specific gravity. Target urine output >0.5 mL/kg/hr (approximately 30-40 mL/hr for average adult). If output <0.3 mL/kg/hr, assess fluid status, reduce infusion rate if hypotensive, and notify physician—may indicate acute kidney injury. Maintain accurate I/O records. Send urine for urinalysis and electrolytes if oliguria develops.

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.

Interactions

With other peptides

  • Standard heart failure therapies (ACE inhibitors, beta-blockers)
  • Diuretics for fluid management
  • Vasodilators for hemodynamic support

With medications

  • !Other IV vasodilators - Other IV vasodilators (may cause excessive hypotension)
  • !Strong ACE inhibitors without dose adjustment - Strong ACE inhibitors without dose adjustment

With supplements

  • Vitamin D3 - Generally safe and may support overall health
  • Magnesium - Generally safe and may enhance peptide absorption

Want the Full Picture?

View the complete Relaxin-2 (Serelaxin) research profile including mechanism of action, clinical studies, effectiveness timeline, and FAQ.

View Full Relaxin-2 (Serelaxin) Profile

Medical Disclaimer

Relaxin-2 (Serelaxin) is an investigational research compound not approved by the FDA for human therapeutic use. This information is for educational purposes only and should not be construed as medical advice. Always consult with a qualified healthcare provider before starting any new supplement or treatment protocol.

Last updated: 2/8/2026

Relaxin-2 (Serelaxin) Protocol — Complete Dosing & Administration Guide | Peptide Initiative