Many modern, inhaled asthma therapies contain a drug combination with a preventive element (long-acting beta-agonists) and a potentially life-saving reliever element (corticosteroid).
Despite being low cost and mass-manufactured, an inhaler is therefore a safety-critical device with associated high-reliability requirements.
By extension, the display indicating the number of doses remaining in an inhaler is also safety-critical and must be equally reliable – otherwise the user may mistakenly assume they have medication left in their inhaler, resulting in a potentially life-threatening situation.
When the FDA introduced guidance requiring that new metered inhalers include a dose-counting mechanism, we used a first-principles approach and probabilistic methods to rapidly design a highly reliable dose counter for AstraZeneca’s Symbicort® product.
Our design offers the user-preferred features of being top-mounted and providing a non-linear motion of a dial on a colour display, enabling a clear dose count from 120 to 0. Moreover, the design consists of only six parts – substantially fewer than competitor devices – and achieves high levels of reliability in an industry-leading low-cost differentiated form factor.
The development of AstraZeneca’s Symbicort® inhaler exemplifies the value of a first-principles approach to R&D, and the appropriate use of novel technology and methods.
Breaking the device down into fundamental mechanisms highlighted inherent design challenges and provided a framework for concept generation and evaluation, with a focus on concepts that satisfied the performance requirements of the device with a minimum amount of complexity.
Probabilistic design methods were used to assess, develop, and generate the manufacturing specification for a reliable concept. This deterministic approach meant that early device testing was less a journey of discovery, and instead essentially confirmation of what was already known.
Our approach reduces risk and uncertainty in R&D and ultimately led to a better product. The same understanding allowed us to confidently write a supplemental New Drug Application (sNDA) which was approved by the FDA without questions on its first submission.
Symbicort® now generates more than $2bn in revenue for AstraZeneca each year.