A Common "Water Pill" for Premature Babies Gets Its First Real Safety Test

What families should know about the Pediatric Trials Network furosemide study (Greenberg and colleagues, 2025) and their baby's lungs

A medicine that doctors have given to premature babies for more than forty years was finally put to a careful, modern test — and the results are mostly reassuring. In a study of 80 very premature infants, a diuretic called furosemide (brand name Lasix) did not add to the overall number of side effects, and did not increase hearing loss or kidney calcium deposits. Its one clear effect was on the balance of salts in the blood, something the care team watches closely and can correct. Importantly, the study was not big enough to prove whether the drug actually helps the lungs [1].

Why this question matters

Babies born very early — in this study, more than three months before their due date — often struggle with their lungs. Their lungs are not finished growing, and the very treatments that keep them alive, like oxygen and breathing support, can also irritate delicate lung tissue over time. This can lead to a chronic lung condition called bronchopulmonary dysplasia, or BPD, one of the most common serious problems of prematurity [2]. Doctors measure BPD mostly by how much extra oxygen a baby still needs at a certain age, and researchers have worked to define it more precisely so they can predict how a child's breathing will do later on [3]. For parents living in the neonatal intensive care unit (NICU), BPD is often the reason a hoped-for homecoming keeps getting pushed back.

The problem this study set out to fix

Furosemide is a "water pill" — it makes the body get rid of extra fluid through urine. The idea behind using it for premature lungs is straightforward: if extra fluid is making stiff, sick lungs work harder, removing some of that fluid might make breathing easier. And in the short term, it often does. Doctors going back to at least 1984, when researchers ran an early trial in premature babies with breathing trouble, noticed that lung mechanics improved for a while, even if lasting benefits were unclear [4]. The trouble is that the science never caught up with the habit. When experts pooled together all the diuretic studies in these babies, they found the studies were small and mostly looked at short-term breathing measurements rather than whether babies ended up healthier [5]. Even so, the medicine spread widely. Surveys found that its use varied enormously from hospital to hospital [6], and furosemide became one of the most frequently given drugs in the NICU [7]. One earlier look at medical records even hinted that babies who got more furosemide had somewhat less BPD — but that kind of study cannot prove cause and effect, because sicker babies and different care styles can muddy the picture [8]. So doctors were giving a drug to many of the most fragile babies, for weeks, without a modern study of how safe it truly was. That gap is exactly what this trial aimed to close [1].

How the study worked

The researchers, part of a national network dedicated to testing medicines properly in children, enrolled babies born before 29 weeks of pregnancy who were one to four weeks old and still needed breathing support [1]. To keep things fair and safe, they left out babies who already had certain kidney, salt, or heart issues. Then they used the strongest kind of study design: babies were randomly assigned to receive either furosemide or a harmless placebo (a dummy treatment), and neither the families nor the doctors knew which was which until the study ended. Three out of every four babies got the real drug. Some received it once a day, and others every six hours, for up to 28 days. The main goal was simply to count and compare side effects. As a preliminary look, the team also estimated each baby's risk of serious BPD using a well-tested prediction tool [9].

What they found

The results are best understood as three simple points. First, furosemide did not make the overall side-effect picture worse. Almost every baby in the study — whether on the real drug or the placebo — had at least one side effect, which is sadly normal for babies this small and sick, and the totals were essentially the same in both groups [1]. Adding furosemide did not tip the balance.

Second, the one real effect was on blood salts. Babies on furosemide were more likely to have disturbances in electrolytes like sodium and potassium — the minerals that keep the heart, muscles, and nerves working properly [1]. This is not surprising, because flushing out fluid also flushes out some salts. The good news is that this is exactly the kind of thing NICU teams monitor with routine blood tests and fix quickly when needed.

Third, two long-standing worries did not come true in this study. Parents and doctors have long feared that furosemide might harm hearing or cause calcium deposits in the kidneys. Over the four weeks studied, neither of those problems happened more often in the furosemide group than in the placebo group [1]. That is genuinely reassuring for short courses of the medicine, though it does not tell us about much longer use over many months.

One more finding matters for how families should think about this drug: the babies who got furosemide were not measurably less likely to end up with serious lung disease or to survive better than those who got placebo [1]. This does not mean the drug is useless — the study was simply too small to answer that question. It means furosemide is best understood, for now, as a treatment that may ease breathing in the moment and appears reasonably safe, but that has not been proven to change the course of the underlying lung disease.

What this means for you and your baby

If your baby's team suggests furosemide, this study offers grounds for calm, informed conversation rather than alarm. A short course did not add to the overall side effects in babies like yours, and the main thing to watch — blood salts — is something the team checks regularly and can correct. It is fair to ask your care team why they are recommending it, how long they plan to use it, and how they will monitor the electrolytes. It is also fair to understand that furosemide is being used to help with breathing right now, not as a guaranteed cure for BPD. Experts agree there still are not enough large studies to say for certain whether diuretics change the ultimate outcome [10].

What researchers are working on next

The natural next step is a much larger study designed specifically to answer the question this one could not: does furosemide actually help premature lungs heal, and not just feel better for a day? Such a study would follow babies for longer, measure their breathing outcomes directly, and build in careful salt-monitoring from the start. Scientists are also studying how babies' bodies process the drug, which could help fine-tune the safest, most effective dose. Families should also know that the medical journal published a small correction to the original article; if any numbers change, this summary will be updated to match [11]. For now, the takeaway is hopeful and honest: a decades-old NICU medicine has been shown to be reasonably safe in the short term, with one manageable side effect, while the bigger question of how much it helps is still being answered.

References

  1. Greenberg RG, Lang J, Smith PB, et al. Furosemide Safety in Preterm Infants at Risk for Bronchopulmonary Dysplasia: A Randomized Clinical Trial. The Journal of Pediatrics. 2025;283:114629. doi:10.1016/j.jpeds.2025.114629 ↩
  2. Thébaud B, Goss KN, Laughon M, et al. Bronchopulmonary dysplasia. Nature Reviews Disease Primers. 2019;5(1):78. doi:10.1038/s41572-019-0127-7 ↩
  3. Jensen EA, Dysart K, Gantz MG, et al. The Diagnosis of Bronchopulmonary Dysplasia in Very Preterm Infants. An Evidence-based Approach. American Journal of Respiratory and Critical Care Medicine. 2019;200(6):751–759. doi:10.1164/rccm.201812-2348OC ↩
  4. Yeh TF, Shibli A, Leu ST, Raval D, Pildes RS. Early furosemide therapy in premature infants (≤2000 g) with respiratory distress syndrome: A randomized controlled trial. The Journal of Pediatrics. 1984;105(4):603–609. doi:10.1016/s0022-3476(84)80431-x80431-x) ↩
  5. Stewart A, Brion LP. Intravenous or enteral loop diuretics for preterm infants with (or developing) chronic lung disease. Cochrane Database of Systematic Reviews. 2011;(9):CD001453. doi:10.1002/14651858.CD001453.pub2 ↩
  6. Laughon MM, Chantala K, Aliaga S, et al. Diuretic exposure in premature infants from 1997 to 2011. American Journal of Perinatology. 2015;32(1):49–56. doi:10.1055/s-0034-1373845 ↩
  7. Stark A, Smith PB, Hornik CP, et al. Medication Use in the Neonatal Intensive Care Unit and Changes from 2010 to 2018. The Journal of Pediatrics. 2022;240:66–71.e4. doi:10.1016/j.jpeds.2021.08.075 ↩
  8. Greenberg RG, Gayam S, Savage D, et al. Furosemide exposure and prevention of bronchopulmonary dysplasia in premature infants. The Journal of Pediatrics. 2019;208:134–140.e2. doi:10.1016/j.jpeds.2018.11.043 ↩
  9. Laughon MM, Langer JC, Bose CL, et al. Prediction of Bronchopulmonary Dysplasia by Postnatal Age in Extremely Premature Infants. American Journal of Respiratory and Critical Care Medicine. 2011;183(12):1715–1722. doi:10.1164/rccm.201101-0055OC ↩
  10. Ó Briain O, Miletin J, et al. Diuretics use in the management of bronchopulmonary dysplasia in preterm infants: A systematic review. Acta Paediatrica. 2024. doi:10.1111/apa.17093 ↩
  11. Greenberg RG, Lang J, Smith PB, et al. Corrigendum to "Furosemide Safety in Preterm Infants at Risk for Bronchopulmonary Dysplasia: A Randomized Clinical Trial." The Journal of Pediatrics. 2025;285:114734. doi:10.1016/j.jpeds.2025.114734 ↩