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Inhaled drug delivery has major advantages over other methods of administration but inhalers can be difficult to use, and those devices which overcome the problems of the majority of inhalers often lack broad availability across molecules and drug classes. A range of therapies in the same type of device would improve proper use of inhalers, which could have a positive impact on treatment.
Benefits of inhalers are obvious
Respiratory diseases such as asthma and chronic obstructive pulmonary disease (COPD) are mostly treated with inhaled drugs, in order to relieve bronchoconstriction and target inflammation in the lungs. There are several advantages to administering these drugs via the inhaled route compared to oral therapy, namely, a faster onset of action, lower drug doses and a better efficacy-to-safety ratio. Drug delivery by inhalation is also painless and more convenient than injectable drugs.
Despite this impressive list of benefits, several drawbacks remain for inhaled medicines. One of the biggest problems relates to the inhaler device through which the drug is delivered. Every type of device is different and requires a specific inhalation technique in order to get a sufficient amount of drug to the lungs. The wide variety of inhalers available can cause difficulties, as the patient must learn the correct use for each one. An incorrect inhalation technique is likely to impact greatly on a patient's daily life, since their asthma or COPD symptoms could be less well controlled than optimally possible.
All types of inhaler have major disadvantages
There are two main types of portable inhaler devices used in the treatment of asthma and COPD: metered dose inhalers (MDIs), including pressurized MDIs (pMDIs) and breath-activated MDIs (BAIs), and dry powder inhalers (DPIs), including single-unit dose DPIs, multi-dose reservoir DPIs and multi-unit dose DPIs. There is a wide variation in design among the BAIs and DPIs in particular, meaning that several techniques must be remembered if they are to be used correctly.
The standard pMDI is the oldest and most often-used inhaler, as it is cheap and supports many different molecules. Nonetheless, a large proportion of patients are unable to use such devices correctly. One of the most common problems is a failure to co-ordinate inhalation with actuation of the device. Patients often actuate the inhaler, therefore releasing the drug, before or at the end of inhalation, and some may even hold their breath while activating the inhaler.
Because of the problems associated with pMDIs, attention has focused on the improvement of inhaler devices to optimize the delivery of medication. BAIs help to overcome the problem of coordinating actuation with inhalation, thus providing the opportunity to improve drug delivery and overall disease control. However, the major drawback of BAIs is that there are only a few drugs available in these devices, due to the high cost involved in developing them. Because physicians cannot necessarily offer all of the medicines a patient needs in a BAI, they are often forced to switch back to a pMDI, or to combine different devices in one treatment regimen.
DPIs offer an alternative response to the difficulties associated with pMDIs. These devices release the drug by passing air from the patient's inhalation effort through medication formulated as a dry powder. Although this partially resolves the co-ordination problem, since the drug is only released when the patient inhales, there are other disadvantages. The wide variety of DPIs available means that inhalation instructions can vary greatly from one to the next. Furthermore, to ensure that most of the drug emitted from a DPI reaches the lungs, it is necessary for the patient to inhale deep and fast. A number of asthma and COPD patients are unable to do so, particularly the elderly, children and people with severe airflow limitation.
The ideal inhaler device does not exist
Both physicians and patients agree that there are certain characteristics to an ideal inhaler. It should be small, easy-to-use and suitable for patients with low inspiratory volume. It should be breath-actuated and only release the drug when all prerequisites for successful inhalation are met. Most importantly, the drug delivery should be flow-independent and multiple automatic feedback mechanisms should exist to reassure the patient that the drug was successfully deposited in the lungs.
However, since there is no single inhaler device combining all of the above characteristics, physicians have to make a choice from the range of available inhaler devices. In this choice, physicians should recognize that patients differ, and devices should be matched to individuals, based around their needs and circumstances. Cost also plays an increasingly important role and many governments will ask physicians to start their patients on a cheap pMDI, only using a more expensive inhaler when necessary.
Despite the apparent range of choices available, the concept of matching an inhaler to a patient becomes redundant if inhaler availability is a problem. Variations in the availability of inhaler devices across treatments exist, and although most molecules are available in both DPIs and pMDIs in the six major markets, availability within a given country may be limited.
A range of molecules delivered in the same type of device could improve treatment
Obviously, when all of the treatments that a patient requires are available in pMDIs, the situation is simplified as there is no difference between the inhalation techniques of these devices. However, DPIs differ significantly and the availability of molecules in certain DPIs may limit a physician's choice. If, for example, a physician recommends Symbicort (AstraZeneca's budesonide/formoterol combination) for a patient, all further drug choices are limited by their availability in the Turbuhaler.
Having a range of molecules available in the same device will allow physicians to prescribe a complete treatment regimen based around that type of device, thereby minimizing errors in inhalation technique. Indeed, some companies market one type of inhaler device with different molecules across drug classes, covering all of the needs of a standard asthma patient. However, these ranges are made up of generic molecules and the newer treatments are not available in the same manner, leaving many asthma and COPD patients struggling with their daily medication.
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