# A Review of Medication Adherence Monitoring Technologies +
## 4 A Review of Medication Adherence Monitoring Systems
### Sensor-Based Systems
#### 4.1.3 Ingestible Biosensors  
The use of biosensors in connected health is in its infancy. However, with the introduction of In vivo communications, it can be expected that the biosensor technology will dramatically improve over time and increase in value to advancing healthcare delivery [102; 120]. Ingestible devices are miniature capsule-looking devices that are digested and swallowed when taken through mouth like solid medications. These devices travel through the gastrointestinal tract and digestive system and collect data about specific physiological parameters [121]. One application of these devices can be for medication adherence monitoring, where data about drug consumption are collected and transmitted to a body-worn or nearby device for further post-processing [122].  
Researchers from Proteus Digital Health, Inc. (Redwood City, CA, USA) have designed a micro biosensor that is intended to be integrated with pharmaceutical oral dose (pill or capsule) for evaluating medication ingestion [74; 123; 124; 125]. The sensor is built from an integrated circuit (IC) with a food particle size. The IC is built from specific materials, including gold. A specific layering design is followed that enables it to act as a battery that collects the current from contacting with the gastric fluid for powering the device. Upon contact with the gastric fluid, the ingestible sensor communicates with a wearable receiver worn by the patient and transmits a unique code. A mobile phone user interface can then identify the ingested medication based on the received code from the ingested biosensor. The designed device have been tested via multiple clinical studies, including humans. Furthermore, 412 subjects were involved in the clinical studies where they have performed more than 20,000 ingestions spanning 5656 days in total. The detection accuracy of medication ingestion was more than 99%.  
Finally, the ingestible IC was proven to be safe prior to conducting the clinical trials, by testing dose on animals.  
MyTMed is another system for medication adherence monitoring that is based on ingestible biosensors [24; 126]. The central part of MyTMed is the digital capsule that can encapsulate oral medication. It is made of a standard gelatin pill capsule that includes a sesame seed size RFID tag. Upon ingestion by the patient, the gelatin capsule dissolves in the stomach and releases the medicine along with the RFID tag. The electrochemical reaction between the tag's electrolytes in gastric acid forms a bio-galvanic battery that enables it to emit a unique code in the forms of packets to a body worn receiver. Eventually, the receiver utilizes short messaging service (SMS) to relay the packets to a cloud server that can be accessed by the caregiver. Based on a 10 participants trail study with 96 ingestion events, the system's detection accuracy was 87.3% [127].  
Advantages of biosensor-based techniques include their ability to detect concurrent medication ingestion events with relatively high accuracy. They are also able to identify the ingested medicine with no computational cost, since each medication has a unique code stored in the in vivo pill. However, as such systems require external receivers to be adhered to the individual's body, many users would object to wearing a banded device throughout the day and possibly for years (when considering people with chronic illnesses). Security and privacy is also an issue, with resource-constraint tags requiring low-energy and lightweight computing cryptographic tools [128].