ABSTRACT:
Metered Dose Inhalers (MDI) are most commonly used type of inhalers mainly used in Asthma and chronic obstructive pulmonary diseases (COPD). In MDI the specicialized devices such as pressurized canisters are used for drug delivery and the therapeutic response totally depends upon optimum drug delivery. MDI are used in emergency such as asthma attack. Breathlessness is the common symptom in asthma in which the patient requires immediate relief. As MDI provide controlled amount of active ingredient, quantitative tests such as Average Weight per Metered Dose, Content per Spray, Content Uniformity, Retention on Adaptor are needed to be monitored. Along with routine analytical methods MDI require special tests which involve measurement of particle size of droplets, spray pattern, vapour pressure, in-vitro deposition on lungs, propellents proportion etc. Aerosol device is a unique packaging system, that drug delivery totally depends upon the design of inhaler. It is very important to consider integral parts of MDI such as metering valves, actuator, spacers etc. Leak testing of pack, flammability of product are another aspects to be considered. In MDI, medication is in solution or suspension form in a pressurized container that contains propellent. On activation MDI releases a fixed dose of medication in aerosol form. Composition involves homogeneous form hence cosolvents, stabilisers, propellent system, lubricants, surfactants are integral part of MDI. The article reveals formulation and important quality control parameters of MDI.