Inhaler devices are the foundation of treatment for chronic obstructive pulmonary disease (COPD) and asthma. They allow for direct delivery of the active drug to the target site of action. This ensures optimal efficacy while minimising systemic adverse effects. Using the inhaled route also has the advantage of a faster onset of action. The patient’s response to treatment with an inhaler device is determined not only by the intrinsic properties of the drug but also by the extent and location of its deposition in the airways. Unfortunately, many patients are at risk of suboptimal clinical response due to poor device technique and subsequent lack of active drug at the target site.

It stands to reason that if a drug requires direct contact with its target site of action to be efficacious, failure to reach this target will result in lowered efficacy. This is true regardless of the pharmacological properties of the actual drug. It is therefore vitally important to treatment success to select an inhaler that the patient is capable of, and trained to use correctly. The choice of inhaler device should be given equal consideration to the choice of drug molecule itself.

There are many different inhaler devices on the market, and each has their specific administration process. The oldest, and perhaps most familiar, device is the pressurised metered dose inhaler (pMDI). Medications available in this format include salbutamol (Ventolin®), fluticasone (Flixotide®), fluticasone/salmeterol (Seretide®) and beclomethasone (QVAR®), amongst others. This device requires the patient to breathe in slowly and deeply while coordinating the actuation of the canister. Therefore, pMDIs may not be suitable for patients with dexterity issues related to osteoarthritis, or those with severe COPD and a low inspiratory flow rate. The most common problem encountered with this inhaler type is a failure to coordinate inhalation with the downward pressure on the canister. Furthermore, if the patient breathes in too fast, there is a risk that the drug may impact the back of the throat and be swallowed, rather than inhaled into the lungs as intended. Other common errors include failure of the patient to hold their breath for ten seconds after inhalation and failing to wait one minute and re-shake the canister between inhalations.

Many of these pMDI administration issues can be solved with the use of a spacer. Spacers are indicated for all children (with mouthpiece or mask), and adult patients who have difficulty in using a pMDI. The basic principle is that the medication is released into a holding chamber, eliminating the need for coordination between inhalation and actuation. Patients can either take one slow, deep breath and hold it for approximately ten seconds or take four tidal breaths. The latter option is more appropriate for children or situations where deep breathing is not possible. While helpful, spacer use is not foolproof. It is important that patients inhale the medication directly after loading the spacer. Drug molecules remain suspended in the air for a finite period, after which they may adhere to the inside of the spacer. Similarly, if patients load the spacer with more than one actuation at a time, molecules can aggregate and fall to the bottom of the spacer. Spacers also require careful cleaning to ensure they continue to deliver the optimal dose. They should be washed in warm water with detergent and allowed to air dry without rinsing. Drying with a cloth or paper towel may cause static to build up which can attract medication to the sides of the spacer.

Breath-activated pMDIs also eliminate the need to coordinate inhalation with actuation. These inhalers contain a spring, which is triggered during inhalation to release the drug. Only a low inhalation flow is required to trigger the device, which is a key advantage of this device type. Patients simply push a lever up and breathe through the mouthpiece slowly and deeply, even after hearing a click. The limitation of breath-activated pMDI use is that the only drugs formulated using this device type are beclomethasone (QVAR Autohaler) and salbutamol (Airomir Autohaler).

In contrast, there are many medications currently formulated in dry powder inhalation (DPI) devices, which include the Accuhaler®, Aerolizer®, Handihaler®, Turbuhaler® and Breezhaler® devices. DPIs also do not require inhalation and actuation coordination. Unfortunately, these devices require high inhalation flow to de-aggregate and disperse the drug powder. This may not be possible for all patients with COPD, and can lead to variability in the amount of drug deposited at the target site. The various DPIs available all have individual and specific processes for their use, with each corresponding step posing a potential for error. For example, Accuhalers® should always be loaded horizontally as the medication can dislodge. Conversely, Turbuhalers® should be loaded in the upright position. Patients may also fail to complete the required two-step Turbuhaler® loading process of twisting the grip both ways. Handihaler® use requires the piercing of a capsule followed by two deep breaths to inhale its contents. Common patient errors with this device may include not piercing the capsule, piercing the capsule multiple times, or even swallowing the capsule.

The newest device to the market is the Soft Mist™ Inhaler (SMI). This device uses a spring to atomise the drug solution which produces a fine mist with a low exit velocity and small drug particle size. Drug release occurs over approximately 1.2 seconds, as compared to 0.15-0.35 seconds for pMDIs. As a result, oropharyngeal deposition is reduced, and delivery to the target site of action in the lungs is optimised. The advantages of this device are that it does not require coordination of actuation and inhalation, and it functions even at low inspiratory flow rates. The Spiriva® Respimat® SMI gained listing on the Pharmaceutical Benefits Scheme (PBS) in October 2015. It requires a specific priming sequence to be performed with each new cartridge. Other medications are also expected to be released in soft mist format.

With the wide range and complexity of devices available, it is easy to see why patients have difficulty adhering to administration instructions over time. Up to 90% of patients using pMDIs and DPIs showed incorrect technique in clinical studies. Even experienced users may not be using their inhalers properly. In one Australian study, 75% of patients using an inhaler for an average of two to three years reported correct technique. However, when asked to demonstrate usage of their inhaler, only 10% did so correctly. The prevalence of incorrect inhaler use increases with age and degree of airflow obstruction. Even if patients may originally understand and follow the correct processes, there is a tendency to lapse into incorrect technique after a short period.

Regardless of the choice of inhaler device, adequate and repeated training in its use is critical to treatment success. Initial counselling should involve a physical step-by-step demonstration of the correct technique. Inhaler technique should also be checked at every visit with a health professional. This can be achieved by requesting the patient to demonstrate their method for using the device. Any errors should be identified and corrected, and the patient should be asked to repeat the demonstration to confirm their understanding.

When reviewing treatment options for patients who are seemingly not responding to inhaled medicines, it is important to consider that improper use of the delivery device may be responsible. Assuming that the dose is inadequate may result in an unwarranted dose increase, which could lead to unnecessary adverse effects.

There are many inhaler devices currently on the market to treat COPD and asthma. To be effective, patient parameters should be taken into account when selecting the appropriate drug therapy and device. Inadvertent misuse is commonplace, resulting in insufficient drug deposition at the target site which may result in a poor clinical response. Pharmacists and other health professionals play a key role in patient education to ensure these devices are used correctly so that optimal outcomes may be achieved.

References:

  1. Bonini M, Usmani O. The importance of inhaler devices in the treatment of COPD. COPD Research and Practice 2015; 1:9.
  2. Haggan M. Spiriva first available therapy in new inhaler technology. Chatswood: AJP; 2015.
  3. National Asthma Council Australia. Inhaler technique in adults with asthma or COPD. South Melbourne: National Asthma Council Australia; 2008.
  4. NPS Medicinewise. Correct inhaler technique for asthma medicines. National Prescribing Service: Strawberry Hills. 2014.

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