10. Inhalations:

Pulmonary administration of medicines by inhalation has traditionally been used to obtain a local effect. This route of administration also has a potential for systemic delivery. Preparations for inhalation include liquids for nebulization, pressurized metered dose inhalers (MDIs) and dry powder inhalers (DPIs).

The implications of the physiology of children of different ages and their ability to use the devices correctly should be considered in the development of paediatric inhalations (8). Depending on their age, children may have more or less difficulty with some of the devices. Problems with the coordination of the inhalation for MDIs and the ability to inhale strongly enough for DPIs determine the effectiveness of getting the medicine into the lung.

The total lung deposition is important for the clinical efficacy of preparations for inhalation. Generally it is affected by the formulation and delivery device controlling size distribution of the aerosol and patient-related factors such as the current disease state. The diameter of the airways is smaller in children than in adults; hence deposition by impact in the upper and central airways may be significantly higher in children (36). The particle size of the aerosol produced by the delivery device needs to be explored during development. 

Nebulized liquids are potentially suitable for young children who cannot use MDIs and DPIs. Their use, however, requires nebulizing devices and access to electricity.

MDIs may be suitable for children from birth when combined with a spacer. A spacer eliminates the need for coordinating the MDI actuation and the start of inhalation. For children younger than 2–3 years a facemask is also required. This can be replaced by a mouthpiece when the child is able to manage
the system.

DPIs may be used for children from the age of 4–5 years, as minimum inspiratory flow is required. DPIs and MDIs are preferred for older children because of their portability and convenience. 

Development of Paediatric Medicines: points to consider in formulation, 
(Annex 5, WHO Technical Report Series 970, 2012)

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