Delivered Dose Uniformity (DDU)

Delivered Dose Uniformity is a measure of how consistently an inhaler or nasal drug product delivers the intended dose from the device. It is used in OINDP testing to assess whether dose delivery is consistent between batches, that the number of dose deliveries are greater than or equal to label claim and that dose delivery remains consistent across the life of the product in the case of multi-dose devices.

A DDU test measures the amount of active drug delivered or emitted from an inhaler or nasal device under controlled test conditions. The dose is usually collected using a sampling apparatus before being recovered and analysed.

Delivered dose and emitted dose are closely related, but they are not always used in exactly the same way. Delivered dose usually refers to the amount of drug available to the user, while emitted dose is often used to describe the amount of drug released from the device during testing.

DDU testing is relevant to all orally inhaled and nasal drug products, including metered-dose inhalers, dry powder inhalers, nebulisers, soft mist inhalers, nasal sprays, nasal aerosols and nasal powders.

DDU testing is important because it helps confirm whether an inhaler or nasal drug product can deliver a consistent dose. Consistent dose delivery supports product quality, patient safety and therapeutic efficacy, while also helping laboratories build reliable methods and generate data that meets regulatory expectations.