Three batches of asthma inhalers have been recalled following manufacturing issues.
People with specific batches of Ventolin Accuhaler inhalers are being asked to replace them immediately.
The manufacturing fault has led to a small number of the devices not delivering the full number of doses, says The Medicines and Healthcare products Regulatory Agency.
Patients who have used the affected batches of Ventolin may find that their symptoms are not relieved as normal by their Ventolin Accuhaler, it says.
If this happens, they are urged to seek medical advice.
Both products are made by Glaxo Wellcome UK Limited.
Bernadette Sinclair Jenkins, the MHRA's regulatory assessment unit manager of the inspections, enforcement and standards unit said that it was important that patients and their families feel confident that their inhalers are safe and effective.
She said: "It is important people check whether they have an affected inhaler.
"We want patients and their families to be confident treatment will be safe and effective when required.
"People with a Ventolin Accuhaler from the affected lots should take them to their pharmacy or their dispensing practice and speak to a pharmacist who will provide a replacement.
"We strongly encourage anyone to report any issues with their inhalers or other medicines or medical devices to MHRA via our Yellow Card Scheme."
Affected Accuhalers should be returned to their pharmacist for a replacement.
Additionally, one lot of Seretide Accuhaler, used for the maintenance of preventative treatment of asthma, is being recalled from hospitals, pharmacies, dispensing practices, retailers and wholesalers in the UK.
The recall of Seretide Accuhaler is pharmacy level because this is only used for maintenance treatment as opposed to a reliever treatment.
These two affected batches of Ventolin Accuhaler and the one affected batch of Seretide were distributed to the UK market.
Only a small proportion of the units are defective.
Other asthma inhalers, including the more commonly used Ventolin Evohaler, are not affected.
Further information is available to patients and healthcare professionals by contacting the manufacturer's customer support team via customercontactuk@gsk.com or calling on 0800 221 441 (option 4).
These are the affected batches:
Ventolin 200mcg – Accuhaler 1x60D - 786G - UK - Expiry date 05/2019
Ventolin 200mcg – Accuhaler 1x60D - 754P - UK - Expiry date 05/2019
Seretide 50/250mcg - Accuhaler 1x60D - 5K8W - UK - Expiry date 04/2019
