A widely available and affordable drug traditionally used to prevent blood clots has demonstrated remarkable effectiveness in treating hospitalized COVID-19 patients when administered through inhalation, according to new research from The Australian National University (ANU) published in eClinicalMedicine.
The international clinical trial, conducted during the early stages of the pandemic, analyzed data from almost 500 patients hospitalized with COVID-19 across six countries. Patients who inhaled heparin were half as likely to require ventilation and had a significantly lower risk of dying compared with those receiving standard care.
Novel Application of Established Drug
Professor Frank van Haren, lead author of the study and Director of the Intensive Care Unit at St George Hospital in Sydney, explained the treatment approach: "All had been hospitalised with COVID-19 but were not yet sick enough to require a breathing machine. The heparin treatment halved their risk of being placed on a ventilator and significantly reduced their risk of dying."
The study builds on earlier research that showed breathing and oxygen levels improved in COVID-19 patients after they inhaled a course of heparin. Unlike its traditional injectable form used for blood clot treatment, the inhaled version targets the lungs directly.
Unique Therapeutic Properties
Professor Clive Page, Emeritus Professor of Pharmacology at King's College London who co-led the international study, highlighted the drug's distinctive characteristics: "Inhaled heparin is anti-viral, anti-inflammatory and anti-coagulant. There's no other drug that has that unique combination."
This triple mechanism of action positions heparin as what researchers term a "pathogen agnostic" drug, meaning it could help treat patients with a whole range of respiratory infections, regardless of which viruses or bacteria are causing the illness.
Broad Therapeutic Potential
The researchers believe the treatment could extend beyond COVID-19 to address other serious respiratory infections. "It doesn't matter what kind of respiratory infection the patient is dealing with, when inhaled, the drug will stop it from infecting the patient and damaging the lungs," Professor van Haren said.
The team is planning to conduct another trial in Europe to confirm the drug's effectiveness in fighting other common respiratory infections such as influenza and RSV. The treatment could also benefit immunocompromised patients, including cancer patients who develop respiratory infections.
Accessibility and Future Development
The drug's affordability represents a significant advantage for global health applications. "Because it's inexpensive, it's much more accessible for those from low-income countries," Professor van Haren noted.
While the findings highlight the potential of inhaled heparin, further development is required before the treatment can be routinely adopted. The researchers are now working on an improved formulation of heparin specifically designed to be given by inhalation.
Pandemic Preparedness
The research team emphasized the treatment's potential role in future pandemic preparedness. "We know it's only a matter of time until the next pandemic, and there are still COVID-19 patients who get very sick. This is a great weapon to have up our sleeve," Professor Page said.
The study was simultaneously presented at the European Respiratory Society International Congress in Amsterdam on September 28, 2025, the leading annual gathering for respiratory research.
