Lecture_19 1.pdf

Aerosol Drug Therapy Systems 1 Ragad Alkaraki Introduction Effective aerosol therapy requires a device that quickly delivers sufficient drug to the desired site of action with minimal waste and at a low cost. Aerosol generators in use include pressurized metere...

Aerosol Drug Therapy Systems 1 Ragad Alkaraki Introduction Effective aerosol therapy requires a device that quickly delivers sufficient drug to the desired site of action with minimal waste and at a low cost. Aerosol generators in use include pressurized metered dose inhalers (pMDIs), dry powder inhalers (DPIs), small and large volume (jet) nebulizers, ultrasonic nebulizers (USNs), and numerous emerging technologies. Pressurized Metered Dose Inhalers The pMDI is portable, compact, and easy to use and provides multidose convenience. A uniform dose of drug is dispensed within a fraction of a second after actuation and is reproducible throughout the canister life. The pMDI and actuator are designed for the specific drug formulation and dose volume to be delivered. Used to administer bronchodilators, anticholinergics, and steroids. pMDI Component A pressurized canister that contains the prescribed drug (a micronized powder or aqueous solution) When the canister is inverted and placed in its actuator, or "boot," the volatile suspension fills a metering chamber. Pressing down on the canister aligns a hole in the metering valve with the metering chamber. Aerosol production takes approximately 20 ms. pMDI Priming Every pMDI should be primed by shaking and actuating the device to atmosphere one to four times before initial use and after storage. Without priming, the initial dose actuated from a new pMDI canister contains less active substance than subsequent actuations. A reduction in emitted dose with the first actuation commonly occurs with a pMDI after storage Breath-Actuated pMDI Incorporates a trigger that is activated during inhalation. The trigger theoretically reduces the need for the patient or caregiver to coordinate pMDI actuation with inhalation. Evaluation of the efficacy of breath-actuated pMDIs in children younger than 6 years is limited Their use should be restricted to older children and adults. Dose Counter A serious limitation of multidose inhalers is the lack of a "counter" to indicate the number of doses remaining in the canister. The pMDI may appear to give another 20 to 60 doses, which may deliver little or no medications as the doses "tail off." Without a dose counter, there is no viable method to determine remaining drug in a pMDI other than manually keeping a log of every dose taken. Dose Counter Factors Affecting pMDI Performance and Drug Delivery Temperature Nozzle size and cleanliness Low temperature (