Using miniature engineering, GSK has become the first pharmaceutical company to use counters in its metered dose inhalers, well-established devices to deliver treatments for people with asthma and other breathing disorders.

Miniature counters for the familiar metered dose inhaler
Asthma sufferers around the world are familiar with 'puffers', the pressurised aerosol inhalers that deliver their medication. Pressurised metered dose inhalers (pMDIs), as they are more correctly called, have been around since the 1950s and are a common delivery device for various treatments for asthma and COPD (chronic obstructive pulmonary disease).

One disadvantage of pMDIs, however, is that they do not give an accurate measure of how many treatments are left. Patients have had to guess the medication remaining during the period of inhaler use, often by shaking the container, keeping a record of use on paper, checking its weight, or even floating it in water.

A significant number wait until the inhaler is empty, leading to possible problems if urgent relief is needed. Some asthmatics carry two inhalers just in case one runs out.

Now, thanks to clever miniature engineering, GlaxoSmithKline has become the first pharmaceutical company to include counters in its pMDIs. The counters - mechanical devices with eight moving parts (and three fixed ones) that are accurate yet small enough to be added to the inhalers - are being introduced in a range of GSK's pMDIs in a number of markets.

Measuring patient benefits
It's not a case of technology for technology's sake. Significant patient benefits have been achieved through a small but important addition to existing pMDIs:

• Patients using pMDIs with counters will not waste medicine by disposing of the container earlier than necessary
• The risk of having an empty pMDI when treatment is needed urgently can be avoided
• Parents are able to accurately monitor their child's treatment and, similarly, carers their patients
• Appointments with physicians for repeat prescriptions can be timetabled more efficiently

The bits that count
At first glance, there is little difference between a pMDI fitted with the new counter and one without. The pictures here tell the story.

Externally, there is a window at the base of the pMDI showing the number of treatments left, and a slightly different cap over the mouthpiece. Inside, there is a combination of bits with names more like the parts of a clock - drive wheels, racks, ratchet pawl, knock gears and unit drums.

Whatever the component names, the package means a big difference for the patient by counting down one unit each time the pMDI is activated. (Strictly speaking, the counter is an actuation counter, not a dose counter. One dose as prescribed by a physician may be one, two or more 'puffs' or actuations of the pMDI. It is the actuations that are counted, not the dose.)

The counter meets guidance from the regulatory authorities, including the fact that even when all the recommended doses have been used and the count reads 000, residue treatment in the canister can still be actuated.
 
A ten-year project
What was involved and how did the GSK research and development staff and manufacturing teams succeed in a project that started about ten years ago?
 
"It was walking into an unknown," says the Manufacturing Strategy manager for GSK at the time. "We agreed at the start there were patient benefits to be gained, but the manufacturing challenges we came across turned out to be things we didn't think existed."

It was a significant project for the company. In the manufacturing function alone, there were about 20 people involved. But manufacturing was not the whole story.

"These things never happen without teamwork, and there were many groups involved," says the MDI Development manager at GSK. "We had an internal team as well as outside suppliers - GSK does not do precision plastic or metal engineering.
 
"We worked with regulatory authorities - we are a closely regulated industry, of course - and carried out laboratory accuracy tests and involved our clinical groups for testing with patients.”

Counting on it
The project manager from the Device Technology Group at GSK adds: "It was a very satisfying project yet not without its challenges. We were not starting with a blank piece of paper, but rather trying to fit small components not dissimilar to the workings of a wristwatch into a device that has been around for some time.

"What we ended with is something that doesn't change the way patients use their inhaler - no extra steps are needed because of the counter. But now patients know how many actuations remain; this will improve treatment and the patient’s or their carer’s confidence that the drug will be there when they need it.”

Patients can count on it.