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Effect of oral urea on hyponatremia and fluid overload in adults with acute and chronic heart failure

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What is this trial about?

A plain-language summary of the goals, design and what participants do

The trial focuses on people who have Chronic heart failure together with Hyponatremia, a condition where the level of sodium in the blood is lower than normal. The treatment being tested is an oral solution containing urea, a simple compound that can help the body get rid of excess water and raise blood sodium levels. Participants will receive either the urea solution at a dose of 15 g or 30 g per day, or a matching placebo. The purpose of the study is to determine whether this approach can normalize low blood sodium and lower the need for hospital care related to heart failure.

During the study, participants will take the assigned medication for up to three months. Blood samples will be collected early in the treatment (around day 15) and again at the end of the 90‑day period to check sodium levels and overall health. Throughout this time, researchers will track any visits to the emergency department, hospital admissions, use of strong fluid‑removing medicines given through a vein, and any deaths related to the heart or blood vessels. Additional observations will include how much urine is produced each day, changes in body weight, length of any hospital stay, and basic safety checks such as kidney function. The study follows a simple schedule of regular medication intake and periodic check‑ups to assess how well the treatment works and whether it is safe.

The research process

The trial runs in 8 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial Visit and Baseline Assessment

    After joining the study you will attend an initial clinic visit where basic health information is recorded.

    A blood sample is taken to measure serum sodium and other laboratory values, and your body weight and 24‑hour urine output are measured.

    The purpose of these tests is to establish your condition before starting the study medication.

  2. Step 2

    Randomization and Receipt of Study Medication

    You will be randomly assigned to receive either urea (the active drug) or a placebo (maltodextrin) that looks the same.

    If you receive urea, the prescribed amount will be either 15 g per day or 30 g per day, based on the study plan.

    Each dose is provided as a powder that you dissolve in water to make an oral solution.

    If you are assigned the 30 g daily dose, you will take two packets of 15 g each in one day.

  3. Step 3

    Daily Medication Intake

    You will prepare the oral solution each day by mixing the powder with the recommended amount of water.

    The solution is taken once daily, preferably at the same time each day, for a total duration of 90 days.

    If you are in the placebo group you will follow the same preparation and timing using the maltodextrin powder.

  4. Step 4

    Self‑Monitoring During the Study

    You should weigh yourself daily and record the result in the provided diary.

    You are asked to note the total amount of urine you produce in a 24‑hour period, if possible.

    Any new symptoms or side effects should be written down and reported at the next study visit.

  5. Step 5

    First Follow‑Up Visit (Day 15)

    Around the 15th day after starting the medication you will return to the clinic for a follow‑up visit.

    A blood sample will be taken to check whether your serum sodium has reached the target range of 135–145 mmol/L, which indicates correction of hyponatremia.

    Additional safety labs, such as kidney function tests, will be performed.

    Your weight and urine output recorded since the start of the study will be reviewed.

  6. Step 6

    Continued Daily Treatment

    You will continue taking the assigned study medication every day, following the same preparation and timing as before.

    Self‑monitoring of weight and urine output should be maintained throughout this period.

  7. Step 7

    Final Visit (Day 90)

    At the end of the 90‑day treatment period you will attend a final clinic visit.

    Blood tests will be performed again to confirm serum sodium level and to evaluate safety parameters.

    Your body weight, 24‑hour urine output, and any hospital visits or emergency department visits for heart failure since the start of the study will be recorded.

    The study team will collect any remaining medication packets and complete the study documentation.

  8. Step 8

    Study Completion

    After the final visit, no further study medication is taken.

    You will receive a summary of the assessments performed during the trial.

Who can join the trial?

4 criteria

  • Must have heart failure (the heart is not pumping blood well) that requires a hospital stay or close outpatient care because of fluid overload, shown by swelling (oedema), fluid around the lungs (pleural effusion), fluid in the lungs (pulmonary congestion), or fluid in the abdomen (ascites), and this must be confirmed by a chest X‑ray or an ultrasound scan.
  • Must be regularly taking a diuretic medication called furosemide (a “water pill”) at a dose of at least 80 mg taken by mouth each day, or an equivalent amount of another diuretic.
  • Must have a low blood sodium level, with a plasma sodium concentration of less than 135 mmol/L (normal is usually 135‑145).
  • Must be 18 years of age or older and be willing to join the study by signing an informed consent form.

Who cannot join the trial?

13 criteria

  • Being medically unstable at admission, which means having shock (your heart cannot pump enough blood) with low systolic blood pressure below 90 mmHg and low mean arterial pressure below 65 mmHg, needing medicines called inotropes or a mechanical heart‑support device (ventricular assist device), or needing a breathing tube placed (orotracheal intubation).
  • Having taken oral urea (the study medication) for three months or more before the trial starts.
  • Having a blood sugar level higher than 250 mg/dL, or a blood sugar between 180‑250 mg/dL together with a low blood sodium level (serum sodium 133‑135 mEq/L) at admission.
  • Being enrolled in another clinical trial at the time you would be randomized.
  • Any situation that might keep you from following the study plan, such as lack of reliable social support, ongoing substance abuse, or inability to understand the study information and sign the informed consent form.
  • Continuing to take thiazides (a type of water pill) after joining the study.
  • Having a terminal illness or being in the final stage of a disease.
  • Having a known allergy, intolerance, or medical reason that makes urea unsafe for you.
  • Having kidney disease with an estimated glomerular filtration rate (eGFR) less than 30 ml/min/1.73 m², which indicates poor kidney function.
  • Having a blood urea level (called plasma urea) of 150 mg/dL or higher.
  • Having a blood test result for NT‑proBNP lower than 350 pg/mL (this test shows how stressed the heart is).
  • Having a history or current episode of uraemic encephalopathy (brain problems caused by severe kidney failure) at admission.
  • Having severe chronic liver disease classified as Child‑Pugh C cirrhosis (the most advanced stage of liver scarring).
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Investigated drugs

Urea (oral solution) is a medication taken by mouth in a liquid form. In this study, it is being tested to see if it can help people with acute or chronic heart failure who have low blood sodium levels (hyponatremia) and excess fluid in the body. The idea is that urea may help raise the sodium level in the blood to a normal range and reduce the amount of extra fluid, which could lower the risk of death from heart problems or the need for a hospital stay. Participants will take the urea for up to 90 days, and researchers will check how well it works at improving sodium levels and preventing serious heart‑related events.

What is already known about the treatment

Urea - This medication is taken by mouth as a powder that is mixed with water to make an oral solution, usually 15 g or 30 g per day. It is an approved substance used in medicine for treating low blood sodium (hyponatremia) and is being studied for heart‑failure patients with fluid overload. Urea works by increasing the amount of solute in the blood, which pulls extra water out of the body and helps raise sodium levels, acting as an osmotic diuretic. It belongs to the pharmacological class of osmotic diuretics.

Investigated diseases

  • Chronic heart failure

    This is a long‑term condition in which the heart’s ability to pump blood is reduced. The reduced pumping leads to fluid buildup in the lungs and other parts of the body. People may notice shortness of breath, swelling in the legs, and feeling tired more easily. Over time the heart muscle can become weaker, causing the symptoms to become more noticeable. The condition usually progresses slowly, with periods of worsening and partial improvement.

  • Hyponatremia

    This is a state where the concentration of sodium in the blood is lower than normal. It often occurs when there is too much water relative to sodium in the body. Early signs can include mild headache, nausea, or feeling unsteady. If the imbalance continues, symptoms such as confusion, muscle cramps, or weakness may develop. The condition can evolve gradually as fluid balance changes.

Trial detailsLast updated 7 Nov 2026
Age18+ yearsPhasePhase IIITrial ID2025-523981-26-03Protocol codeNUT-URE-2025-01Estimated enrolment210 patientsSponsorNutricion Medica S.L.

sourced from the EU Clinical Trials Register and site verification

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