Texture Analysis in action: Metered Dose Inhaler test

The METERED DOSE INHALER or MDI (A/IS) delivers a precise, reproducible dose of drug accurately to the deep lung. 

It is also well accepted by patients who depend on MDI’s in their treatment and therefore it is essential to constantly improve this technology. Patients need to rely on their inhaler to provide them with the required medication which is often at a crucial time when physical strength may be very low.

The metering valve, whose performance is assessed with this test, is a critical component of a finished metered-dose inhaler.

Assessment of inhaler performance

The interaction between the elastomeric components and the formulation can significantly affect product performance.

A change in formulation, for example implementing a new propellant system, may necessitate a complete redesign of the valve system in order to successfully deliver the drug with the minimum of difficulty.

Some more information on this fixture: 

Inhalation Drug Delivery via Metered-dose Inhalers
Aerosol route of administration targets drugs directly to the lungs and offers advantages of bypassing the first pass elimination, reducing the dosage frequency and minimising the extent of adverse drug reactions. This, in turn, improves the therapeutic effect-toxicity ratio.

The metered-dose inhaler (MDI) delivers a precise, reproducible dose of drug accurately to the deep lung. It is also well accepted by patients who depend on MDI’s in their treatment and therefore it is essential to constantly improve this technology. Patients need to rely on their inhaler to provide them with the required medication which is often at a crucial time when physical strength may be very low. Therapeutic performance of aerosols is affected by various factors such as actuator tube design, orifice diameter, concentration of surfactant in the system, vapour pressure of propellants, efficiency of valve crimping and particle size of the plume emerging from the inhaler.

The metering valve is a critical component of a finished metered-dose inhaler. A complex assembly of at least seven component parts which are made of various materials and are commonly from different sources. the valve is undoubtedly the most critical MDI packaging component in terms of the manufacturing quality required to ensure consistent correct performance.

The typical metering valve consists of two coupled valves.  It is essential that under all conceivable methods of use, during depression of the valve stem the inner seal closes to isolate the container contents before the outer seal opens to allow discharge of the chamber contents. A reversed sequence may allow ‘continuous spraying’, the absence of which must be verified in evaluating valves for inhalation use, because this could cause erratic dosing or even serious overdosage.

The elastomeric sealing components are also particularly critical. Important characteristics of the rubber components include their composition and degree of curing which control the physical properties and swelling characteristics in situ. The interaction between the elastomeric components and the formulation can significantly affect product performance. A change in formulation, for example implementing a new propellant system, may necessitate a complete redesign of the valve system in order to successfully deliver the drug with the minimum of difficulty.

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We can design and manufacture probes or fixtures for the TA.XTplus texture analyser that are bespoke to your sample and its specific measurement.

Once your measurement is performed, our expertise in its graphical interpretation is unparalleled. Not only can we develop the most suitable and accurate method for the testing of your sample, but we can also prepare analysis procedures that obtain the desired parameters from your curve and drop them into a spreadsheet or report designed around your requirements.

For more information on how to measure texture, please visit the Texture Analysis Properties section on our website.

The TA.XTplus texture analyser is part of a family of texture analysis instruments and equipment from Stable Micro Systems. An extensive portfolio of specialist attachments is available to measure and analyse the textural properties of a huge range of food products. Our technical experts can also custom design instrument fixtures according to individual specifications.

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