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Medication Adherence


With the advent and introduction of health information technology tools into the marketplace, the industry is pressed to discover effective methods for implementing and using these tools to improve the standard of care for patients.  Under examination is using these tools to track medication adherence (or compliance with); defined as the extent to which patients take medications as prescribed by their health care providers [1].

Tracking a patient's adherence is incredibly critical in managing care overall; however, until now healthcare providers had no way of ascertaining if patients were complying with medication regimens unless the patients told them or kept their own register.  Health information technology (health IT) applications such as electronic health records (EHRs) by providers and personal health records (PHRs) have increased access to varied data sources for tracking medication adherence, but accuracy and relevance of data and data sources is still under development and standardization

Areas of Current Investigation

Fifteen projects funded by AHRQ are examining how to track medication adherence as a part of their overall project goals. Some of the AHRQ-funded projects are evaluating if presenting medication adherence information to providers and/or patients via health IT solutions impacts patient adherence to prescribed medications.  Evaluating different forms of data collection to determine medication adherence include examining data collected by:

  • Days covered and fill adherence
  • Medication possession ratio within e-prescribing systems
  • Adherence by class
  • Patient self-reported adherence

Another area of investigation is determining reasons for non-adherence.

Days covered and fill adherence

Several projects link electronic prescription information to prescription fill information to present providers with information on adherence to medications during a patient encounter.  Prescribing date and duration (usually via refill amounts) are available within the provider's electronic prescribing (e-prescribing), EHR, or health information exchange (HIE) system.  Pharmacy information includes fill date and days supplied information.

Medication possession ration within e-prescribing systems

The medication possession ratio (MPR) is a formula used to determine compliance that is measured from the first to the last prescription.  The denominator is the duration from the start period to the completion of the last prescription, and the numerator is the days supplied over that period from first to last prescription [2].

Adherence by class

Patients with chronic conditions create a different data set when analyzing medication adherence because of the nature of following a medication regimen.  Some projects are calculating adherence to medications by therapeutic class, which involves additional analysis to group medications.  A standardized industry coding system in use for medication classes does not currently exist, requiring the AHRQ projects to group medications into classes as part of their projects.

Patient Self-Reported Adherence

Capturing patient self-reported information on adherence using various health IT tools or patient interviews is being investigated, including:

  • An automated telephony system for pre-visit interviews
  • Tracking diagnoses by following up with patients to check their outcomes after the initial visit in the ambulatory care setting
  • A Web-based platform that presents an interactive "character" to the patient to collect information about patient adherence

Determining Reasons for Non-Adherence

In general, understanding whether the non-adherence issues are intentional are critical to gaining a better understanding of adherence issues for patients.    Reasons for non-adherence discovered by the grantees includes: cost, side effects, incorrect self-administration, 'just-in-case' medications, system errors, and non-intentional issues such as forgetting to take the medication or not picking up the medication from the pharmacy.

Associating Prescription Data with Pharmacy/Payer Data

The primary method used to determine medication adherence using electronic data sources is via linking electronic prescription information from the e-prescribing system with pharmacy fill information.  The two most common sources of fill information are pharmacy claims data provided by the insurer (or pharmacy benefit manager) and via the medication history transaction available via the Surescripts e-prescribing network.

Challenges inherent to using insurer pharmacy data include: low cost generics, access to Medicare Part D data, timeliness of data, failed matches and patient-specific instructions.  Using Surescripts medication history data can also be challenging, as patients may not always pick up prescriptions that were filled which is not captured in this data.  Further, different sources of electronic medication information use different codes for each different type of medication, resulting in data mapping challenges.


The challenges and opportunities associated with obtaining and using medication adherence information in real-world clinical settings includes: identifying accurate electronic gathering methods, ensuring accuracy of data and creating a standard tool to collect such data.  These projects continue to provide interesting insight into how many participants in the healthcare industry may use health IT to further their knowledge of their patients? adherence and are worthy of continued study.  Tracking medication adherence through health IT will be a critical advance in giving physicians and other healthcare providers the tools they need to provide better care for their patients.


1. Osterberg L, Blasche T  Adherence to Medication. N Engl J Med 2005; 353: 487-497.

2. Blanford L, Dans PE, Ober JD, Wheelock C. Analyzing variations in medication compliance related to individual drug, drug class, and prescribing physician. J Managed Care Pharm. 1999;47-51.

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