Recent AAPS PharmSciTech review article focuses on techniques used in preparing dry powders.
Delivering drugs through the respiratory tract is an effective route of administration, especially for drugs with poor oral bioavailability. In the recent AAPS PharmSciTech review article Respiratory Tract: Structure and Attractions for Drug Delivery Using Dry Powder Inhalers, Elkasabgy, Adel, and Elmeligy describe different types of inhalation devices, with an emphasis on advances in dry powder inhalers (DPIs).
Nebulizers aerosolize liquid solutions, and do not require propellants or actuation-breath coordination. Metered-dose inhalers (MDIs) deliver a liquid formula through a metering valve in the device and require actuation-breath coordination. Soft mist inhalers (SMIs) require no propellant nor coordination of actuation and breathing while still administering the drug quickly and effectively. DPIs rely on the patient’s inspiration but do not require actuation-breath coordination. The following table provides an comparison between these different devices.
MDIs metered dose inhalers, SMIs soft mist inhalers, DPIs dry powder inhalers
*New breath-actuated MDIs do not require actuation-breath coordination
In particular, dry powder inhalers (DPIs) use “dry powders with or without carrier to improve flowability and drug delivery to deep lungs,” share the authors. This review article illustrates different types of DPIs that are available and different methods for the preparation of powder formulations.
To be delivered via inhalation, drug molecules must overcome natural barriers in the lungs, and they must meet particle size limits depending on the intended target. The inhalation device is also imperative to successful administration of inhaled therapies. Certain formulations will work better with certain devices, plus patient compliance, including age and medical conditions, must be taken into consideration.
Illustrative sketch of the inhaled particles journey from the inhaler passing through the lung till absorption into systemic circulation
Overall, drug delivery through the respiratory route is a promising option for many molecules that suffer from poor bioavailability through other administration paths. “[F]ormulating the right formula and choosing the correct inhaler is a must if efficient drug delivery is needed.