Metered-dose inhaler actuation with breath inhalation

Larsen, J.S. Hahn, M. Kochevar, J.W. Morris, R.J. Kasier, H.B. Weisberg, S.C. Halverson, P.C. Quessey, S.N. Administration errors with a conventional metered dose inhaler versus a novel breath actuated device. Ann. All. 1993, 71, 103-106. 

Timing of the aerosol entry at a particular point in the breathing cycle can have a profound effect on deposition. With the metered-dose inhaler without a spacer, poor synchronization of inspiration with the firing of the valve can result in a substantial loss of the aerosol bolus. For this reason, breath-actuated valves have been developed [91-93]. 

Metered-dose inhaler (MDI) Canister held inverted Formulation (CFC, HFA, solution, suspension) Actuator cleanliness Addition of a spacer device Inspiratory flow (slow, deep) Breath-holding Coordinating actuation with inhalation Priming and shaking the device... 

Riker Laboratories, now 3M Healthcare, invented the pressurised metered dose inhaler (MDI) in 1955 when they combined the atomising power of CFCs and a metering valve design. The great majority of valves still use this basic retention valve principle, and hence pressurised MDIs (pMDIs) are all similar in appearance and operation when used with a standard actuator in the normal press and breathe manner. 

Many drugs have been formnlated for use with pressurized metered-dose inhalers (pMDIs) (Table 1). The main market for these devices is in the treatment of asthma, allergic diseases, and chronic obstructive pulmonary disease (COPD), for which approximately 500 million pMDIs are produced each year. Their major selling points are that they are cheap and portable. Despite their huge sales, there is increasing concern that the dose of drug patients with asthma receive will vary considerably due to their inhalational technique and to a lesser extent to the variabihty of dose delivery from the pMDI. It is likely, however, that the popularity of pMDIs will continue due to various modifications and additions that are aimed to help with inhalational technique and improve drug delivery. Examples of these include breath-actuated devices, discussed in this chapter, and spacer devices discussed in a subsequent chapter. 

The AERx, developed by Aradigm (Hayward, CA), is a metered dose liquid inhaler designed to deliver various pharmaceutical compounds to the peripheral lungs. The system, as shown in Fig. 10, consists of a unit dose disposable container equipped with a nozzle array, a piston assembly, and electronics associated with breath actuation and compliance monitoring functions. ... 

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