Pressurized metered-dose inhalers pMDI

As described in Section 3.3 in more detah, particles in the aerosol cloud should preferably have an aerodynamic diameter between 0.5 and 7.5 pm. Currently three different types of devices are used to generate aerosol clouds for inhalation nebulizers (jet or ultrasonic), (pressurized) metered dose inhalers (pMDIs) and dry powder inhalers (DPIs). The basic function of these three completely different devices is to generate a drug-containing aerosol cloud that contains the highest possible fraction of particles in the desired size range. 

Aerosols can be generated by three main drug delivery systems nebulizers, pressurized metered dose inhaler (pMDI), and dry powder inhaler (DPI). 

Pressurized metered-dose inhaler (pMDI) propellants... 

Three different types of inhalers are used to deliver drugs to the deep lung. Nebulizers, the oldest type of inhaler, work by producing a mist of aqueous, drug-containing droplets. The drug can be either dissolved or suspended in the water phase. In a pressurized metered dose inhaler (pMDI), the drug is... 

The modern pressurized metered dose inhaler (pMDI) was developed between 1955 and 1956. However, the pMDI had its roots in research carried out many years before.During the 1930s and 1940s, the discovery of liquefied propellants (chlorinated-fluorocarbons or freon propellants) such as CFC12, CFC114, CFCll, and CFC22 was a major step in the realization of a portable inhaler. However, the first pMDI was not invented until 1956, when the metering valve used in the device was developed and patented. ... 

The efficacy and safety of salbutamol inhaled using a dry powder inhaler has been compared with salbutamol inhaled using a pressurized metered-dose inhaler (pMDI) in a randomized, open, crossover study in 12 patients with moderate to severe asthma. A total of 1600 micrograms of salbutamol was given on two separate days in a cumulative dose fashion in increments of 100,100,200, 400, and 800 micrograms at 3-minute intervals. FEVi rose progressively with each increment. The dose-response curves showed that powdered salbutamol was 3.0 times as potent (Cl = 1.8,5.8) as salbutamol from... 

Kunka R, Andrews S, Pimazzoni M, Callejas S, Ziviani L, Squassante L, et al.. From hydrofluoroalkane pressurized metered-dose inhalers (pMDIs) and comparability with chlorofluorocarbon pMDIs. Respir Med 2000 94(suppl B) S10 S16. 

The pressurized metered-dose inhaler (pMDI) for the delivery of antiasthma drugs originated in the U.S. cosmetic industry. George Maison, the president of Riker Laboratories, and Irvin Porash, who worked in Riker s pharmaceutical development laboratory, are credited with the development of the first pMDI (32). Experiments were conducted to formulate pressurized aerosols of isoproterenol and epinephrine, which had been dissolved in alcohol, using the freon propellants 12 and 114. 

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. 

II. What Is a Pressurized Metered-Dose Inhaler (pMDI) ... 

The pressurized metered dose inhaler (pMDI) is a pocket sized, hand-held drug delivery system designed to deliver consistent small doses of medicines directly to the patient s lungs. The essential constituents are the medicine, the propellant, and a storage canister, a metering valve, and an actuator. This chapter is concerned with the propellants. It addresses... 

Common suspension pressurized metered dose inhalers (pMDIs) suffer from delivering small amounts of a drug to the lungs and also... 

Inhaled respiratory therapentic agents are, as a rule, administered as aerosols. The aerosol may be an aqneons solution or suspension of the drug generated by a compressed air or ultrasonic nebulizer. Alternatively, the aerosol may be generated by a pressurized metered-dose inhaler (pMDI), a device that contains a solution or suspension of the drug in a volatile propellant such as chorofluorocarbons (CFCs)... 

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