# A Review of Medication Adherence Monitoring Technologies +
## 3 Related Work  
Medication adherence is a crucial issue that needs to be monitored and assessed continuously. Thereafter, improvements can be made once deviations are detected. In the past, a wide number of review studies that addressed the medication adherence problem have been created. However, most reviews studied the medication adherence from a clinical point of view along with interventions [6; 7; 8; 9; 20; 21; 27; 34; 35; 38]. Moreover, only a few studies have presented the electronic-based interventions [29; 42; 44; 45; 52; 53; 54; 55; 56]. Little attention has been paid towards employing technology in medication adherence monitoring and enhancement as compared to the traditional modalities. These reviews have elucidated the role of technology-based solutions for medication adherence assessment, the potential benefits and limitations, but, no detailed discussion on the cyber-physical system, including system design, hardware development, and data analytics of these solutions were given.  
A rare number of studies describe technology-based interventions for adherence monitoring and enhancement. For example, [PERSON] et al. [54] presented an overview of a number of electronic systems and methods of medication measurement. Other review articles have discussed the smartphones' applications [55], and tablet [44] applications technology for medication adherence that are in the form of automated reminder systems. In [45], the authors summarized some medication adherence measurement methodologies for older people that use alert and reminder systems, along with their potential advantages. In [57], some technological medication reminder approaches have been briefly described. It is worth mentioning that only a recent study by [PERSON] et al. [58] has reported some commercially available technology-based solutions. In addition, they provided a brief discussion of some clinical studies that involved electronic medication monitoring. It also discussed the challenges associated with medication monitoring technologies from data analytics, reliability, and scalability sides. It is obvious that these survey studies are limited in providing a detailed discussion of the technical sides of the different technology-based sensing or monitoring approaches for medication adherence.  
Although we previously covered some recent applications for medication adherence monitoring [59] that rely on modalities such as sensor networks and proximity sensing, there is still a lack of comprehensive state-of-the-art survey studies concerning the recent medication adherence monitoring approaches. The main objective of this paper is to explore this topic further by extending the discussion on the monitoring systems, expanding the list of surveyed papers, taking account of other medication monitoring systems such as ingestible biosensors, and discussing the trade-offs of each technology in multiple dimensions. To our knowledge, this is the first review that addresses medication adherence monitoring approaches using a variety of emerging technologies. It is the first that looks at the medication adherence monitoring approaches from a technical point of view with the aim of promoting the future systems such that they help in filling the gaps that existed in the current ones.