The Power of Medication Adherence Packaging
Introduction.
What is medication adherence and medication compliance?
Medication adherence and medication compliance are often used interchangeably – however, there are slight differences. Medication adherence considers the patient-provider interaction. It refers to the degree to which an individual takes their medication as agreed upon with their provider. Medication compliance relies more heavily on the prescriber’s authority, referring to the degree to which a patient takes their medication as directed by their provider 1.
For the purposes of this whitepaper, adherence and compliance are used interchangeably. If a patient takes a medication as prescribed, the patient is adherent. If a patient does not always take their medication as prescribed, they may be non-adherent. Non-adherence depends on the proportion of doses taken correctly. It can also manifest in several ways.
Adherence & Compliance
While there are subtle differences, the terms medication adherence and medication compliance can be used interchangeably. If a patient takes a medication as prescribed, the patient is adherent or compliant.
Types of non-adherence
Primary Non-Adherence
Perhaps most obvious form of non-adherence is primary non-adherence. Primary non-adherence refers to when a patient never fills or takes a medication their doctor prescribed. Though a clinician identified a need for treatment, the patient never actually starts this treatment. Thus, they would be non-adherent to their medication regimen1.
Non-Persistence & Unintentional Non-Adherence
Non-persistence involves a patient discontinuing medication without their doctor’s consent.
Unintentional non-adherence occurs when a patient experiences external barriers to adherence. Barriers may include the high cost of medication, or the patient’s lack of healthcare access, which can prevent patients from filling or taking their medications after starting them.
Even if a patient fills and takes their medication, they may still be non-adherent depending on how they take their prescription. A patient may miss doses, take extra doses, take the wrong number of doses, or take a dose at the incorrect time.
Why medication adherence
is important.
For the patient, non-adherence can lead to worsening disease, decreased function, and a worse quality of life1. For example, a study of over 11,000 diabetes patients measured adherence rates among participants. Non-adherent individuals demonstrated increased blood pressure, glycosylated hemoglobin, and cholesterol levels. Likewise, non-adherent individuals had higher rates of hospitalization and death compared to adherent individuals2.
Non-optimized medication therapy results in $528.4 billion yearly in preventable costs.
Non-adherence does not just affect the patient. It also has broad implications for healthcare systems and public health efforts. For example, non-adherence can lead to hospital visits and readmissions. This can burden the healthcare system with otherwise preventable medical events, increasing healthcare spending and dwindling resources. One study found 26% of all hospital readmissions were medication-related, and 23.8% of those were due to non-adherence3. As a result, non-optimized medication therapy results in $528.4 billion yearly in preventable costs. Likewise, medication non-adherence is a significant public health issue1.
Causes of medication-related hospital readmissions
How Do You Measure Adherence?
There are various ways to measure medication adherence, from patient observation to pharmacokinetic modelling. However, no gold standard exists for measuring a patient’s medication compliance. This section describes different methods of collecting and interpreting adherence data.
Collecting adherence data
Clinicians can directly monitor compliance using observation and pharmacokinetic (PK) modelling. These models evaluate the relationship between a patient’s adherence patterns and the drug concentrations in their blood or urine. A patient whose drug concentration is within therapeutic range is likely adherent. A patient whose drug concentration is not within therapeutic range is likely non-adherent. Direct methods such as these are usually the most accurate, but are also expensive and difficult to implement and scale1,4.
Clinicians can also determine adherence via indirect techniques. These methods include patient diaries, patient questionnaires, electronic medication monitors, adherence packaging, pill counts, and a patient’s clinical status1. These techniques, especially those that are patient-reported, can be less accurate. However, they are usually less costly to implement and easy for patients and providers to use.
Adherence can be monitored using:
Pharmacokinetic (PK) modelling
Patient diaries
Patient questionnaires
Electronic medication monitors
Adherence packaging
Pill counts
Patient’s clinical status
Interpreting adherence
The medication possession ratio (MPR)
One method professionals use to quantify medication adherence is the medication possession ratio or MPR. The MPR is the sum of the days' supply for all fills of a given drug over a particular time period, divided by the number of days in that time period5. This value is expressed as a percentage.
Despite no established MPR standard, adherence studies commonly use an MPR of 80 as the threshold to define adherence. That means if a patient’s MPR is 80 or above, a clinician would consider the patient to be adherent.
The MPR Value
While there is no standard, adherence studies commonly use a medication possession ratio (MPR) of 80 as the threshold to define adherence. This means patients take their medications as prescribed 80% of the time.
The MPR value is arbitrary, as there is no standard threshold that describes adherence or non-adherence. This is because the impact of the MPR, or the “adherence level”, is relative to the condition and medication itself. For example, some disease states are incredibly sensitive to a single dose of medication. For others, non-adherence has less of an impact. Additionally, the MPR does not distinguish between different types of non-adherence. Different types of non-adherence can have varying clinical impact. For example, a provider may consider both a missed dose and a late dose to be examples of non-adherence. However, a missed dose would likely have a greater clinical impact than a late dose4.
Proportion of days covered (PDC)
Another common measure for medication adherence is known as proportion of days covered or PDC. This is a more conservative way to measure adherence compared to the MPR and adjusts for limitations of the MPR measurement.
PDC is the number of days “covered” with prescribed medication over a period of time, divided by the number of days in that time period. This value is expressed as a percentage.
PDC is a more conservative way to measure adherence compared to the MPR and adjusts for limitations of the MPR measurement.
Unlike MPR, PDC corrects for situations where a patient refills a prescription early. For example, if someone refills a prescription 10 days early, the MPR measurement would include overlapping days of medication supply. That means the MPR value would rise over 100%. On the other hand, the PDC measurement would move forward those 10 days in the schedule. The 10 doses from the early refill would begin on the first day the patient does not have medication from their previous dispensing. With this, the PDC measure can never be over 100%.
Another advantage of PDC is it takes into consideration all medications in a patient’s regimen, whereas MPR measures an average for each medication in a regimen. This means a patient could have a high MPR for one prescription and a low MPR for another prescription. When those MPRs are averaged, the patient’s overall MPR may seem acceptable when it is not.
When using PDC, only days where all medications in a patient’s regimen are available to the patient are considered “covered” days.
As a result of these advantages, PDC is growing as a preferred measure5.
