Studies have shown that approximately 50% of patients do not take their chronic medications as prescribed. Nonadherence can include delaying or not filling a prescription, skipping doses, splitting pills, or stopping a medication early. Nationally, nonadherence costs the healthcare system an estimated $100 to $289 billion annually. Not only does nonadherence increase costs, but it also leads to poorer health outcomes for patients.

What's the Difference between Adherence, Compliance and Persistence?

Medication Adherence: the extent to which a patient’s behavior (e.g. taking medications with respect to timing, dosage, and frequency) corresponds with agreed-upon recommendations from a health-care provider

Medication Compliance: the extent to which a patient passively follows the advice of their provider

Medication Persistence: the duration of time from initiation to discontinuation of therapy

Note: Adherence is measured over a period of time and reported as a percentage, whereas persistence is reported as a continuous variable in terms of number of days for which the therapy was available. It is important to take into consideration both factors as clinical outcomes are affected not only by how well patients take their medications but also by how long they take them.

• Delay or not filling a prescription
• Not picking up a prescription
• Skipping doses
• Splitting pills or stopping a medication early
• Not refilling a prescription

Factors Limiting Adherence

1. Social and economic factors (e.g. language, literacy, insurance/costs, healthcare facility accessibility, cultural beliefs)
2. Health care system/HCT (health care team) factors (e.g. long wait times, lack of continuity of care, poor provider-patient relationship, weak education, restricted formularies)
3. Condition-related factors (e.g. chronic diseases, depression, psychotic disorders, disability, symptoms)
4. Therapy-related factors (e.g. complexity of regimen, difficult administration techniques, side effects)
5. Patient-related factors (e.g. physical impairments, lack of motivation, psychosocial stress, anxiety, anger, alcohol or substance abuse)

Measuring Adherence

There are both direct and indirect measures of adherence. In some instances, providers might wish to measure adherence directly by measuring the concentration of drug levels in the blood. More commonly used, however, are indirect measures of adherence which include patient questionnaires, pill counts, refill rates, and clinical response.