While inhalation is the drug administration route of choice for the treatment of asthma and chronic obstructive pulmonary disease (COPD) a review in this month's Respiratory Medicine journal claims that the diseases are still poorly controlled - with inhaler devices partly to blame for the disappointing statistics.
While pressurised metered dose inhalers (pMDIs) are the most frequently prescribed inhalers, the report authors state that high numbers of patients fail to use the devices correctly, even after repeated tuition.
The report cites a study of 115 asthmatics which revealed that 72 per cent of patients who received no instruction were unable to use their pMDI correctly, and only 48 per cent after physician training. However, a large Spanish study makes for more stark reading - with 91 per cent of patients, 85 per cent of physicians and 72 per cent of nurses unable to use a pMDI correctly.
"Even with the correct inhalation technique, pMDIs are inefficient, often delivering less than 1/3 of the emitted dose to the lungs and less than half of the emitted dose to the peripheral airways compared with DPIs [dry powder inhalers]," the report authors say.
"A high proportion of drug [is also] deposited in the mouth and oropharynx which can cause local as well as systemic side effects due to rapid absorption."
While DPIs offer advantages over pMDIs, this kind of inhaler still comes with its own set of drawbacks according to the report.
A number of products currently on the market (including GlaxoSmithKline's Rotahaler, Boehringer Ingelheim's Handihaler and Novartis' Aerolizer), for example, require users to load each dose into the inhaler immediately before use. Aside from being rather inconvenient, this also removes the option of direct dose counting and therefore monitoring of patient compliance.
Other DPI disadvantages include the necessity for patients to generate sufficient inspiratory flow to trigger dosage and drug particles of optimum size, the variability in particle size that can lead to ineffective drug deposition in the mouth or oropharynx, and difficulty in loading doses into the inhaler.
While the report authors catalogue some of the downfalls of the available inhalation devices, they by no means discount their importance in the treatment of diseases such as asthma and COPD.
Quite the contrary, in fact, stating that while the drugs that are delivered by inhalers garner much attention, the inhalation devices themselves are largely disregarded.
"This is a regrettable situation since inhaled drugs are the most effective therapy available for asthma and COPD," says the report, suggesting that improvements in inhaler technology as well as physician and patient education could help enhance asthma management and control.
"In other words, an old but well-known drug in a new, more reliable inhaler is probably more useful than a new drug in an old (flawed) inhaler."
The report authors suggest mechanisms that would feature on the ideal inhalation system, including the requirement that it be simple to use (particularly for children), be breath activated, multidose and refillable, and be equipped with a dose counter that not only counts the dosages but also indicates the number of correctly performed inhalations.
Although the pharma industry understandably tends to focus on developing new drugs to improve therapeutic treatment for patients, the authors of this paper seem to think that in the case of asthma and COPD, attention could profitably be directed elsewhere:
"In the near future, it seems unlikely that improvements in disease control will be due to the introduction of new and novel therapies, but rather from improvements in how these pharmacological agents are delivered to the lung, i.e. improvements in inhaler technology and design."
The article, entitled Importance of Inhaler Devices in the Management of Airway Disease, is available online here .
