GSK Plc is voluntarily recalling more than 593,000 Ventolin asthma inhalers from U.S. hospitals, pharmacies, retailers and wholesalers due to a defect that may cause them to deliver fewer doses of the medicine than indicated, the British drugmaker said on Tuesday.

The company said it had received an elevated number of product complaints about a bulging of the outside wrapper, indicating a leak of the propellant that delivers the medicine.