Regimen and device compliance: key factors in determining therapeutic outcomes.

The two most important differences between inhaled and oral therapy are (1) the lungs have evolved to exclude foreign material while the gut has evolved to take in large amounts of foreign material, and (2) even if patients adhere to a treatment regimen (regimen compliance or adherence), they may fail to derive any benefit from using an inhaler due to failure of drug delivery (poor device compliance). In other words: True compliance = regimen compliance x device compliance. Aerosol scientists, building on the observations of those working in the field of industrial hygiene, have developed devices that largely address the challenge of bypassing the lung's defenses, in that current devices generate aerosols that contain a significant proportion of particles in the range of 1-5 microm. These have a relatively high probability of entering the lungs and depositing through impaction and/or sedimentation. The development of delivery systems for systemically acting drugs has led to further refinement. The second issue, that of patient behavior, has, until very recently, received very little attention from those developing devices. Regimen compliance involves taking the medication at the suggested times. Device compliance (using the device optimally) is dependent on competence and contrivance. A patient taking a tablet before rather than after a meal is likely to receive some therapeutic benefit even if the effect is suboptimal. A patient whose device compliance is poor because either they are not competent to use the device or contrive to use it in an ineffective manner may derive little or no benefit even if they are scrupulously adhering to their treatment regimen. Lack of precision in the use of the terms "compliance" and "adherence" has contributed to the failure to build in features that may help address issues relating to patient behavior. The resurgence of interest in developing devices that can be used to deliver potent systemically acting drugs has, out of necessity, led to the development of systems that help minimize the impact of poor competence or contrivance on drug delivery. There are suggestions, that need to be confirmed, that regimen compliance (adherence) can be influenced by providing feedback. In the absence of formal studies, comparison of the high-tech and low-tech approaches to improving device compliance incorporated into novel devices might provide valuable insights into what aspects of feedback are important in the clinical setting.