Compliance (medicine)

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Compliance (or Adherence) in a medical context refers to a patient both agreeing to and then undergoing some part of their treatment program as advised by their doctor or other healthcare worker. Most commonly it is whether a patient takes their medication (Drug compliance), but may also apply to use of surgical appliances (e.g. compression stockings), chronic wound care, self-directed physiotherapy exercises, or attending for a course of therapy (e.g. counselling).

It has been estimated that in developed countries only 50% of patients who suffer from chronic diseases adhere to treatment recommendations.[1] Compliance rates during closely monitored research studies are usually far higher than in later real-world situations (e.g. up to 97% compliance in some studies on statins, but only about 50% of patients continue at six months).[2]

One third of patients with hypertension resitant to triple therapy may be noncompliant[3].

Nonadherence may affect the patient's own immediate health or have implications for the wider society (e.g. failure to prevent complications from chronic diseases, formation of resistant infections or untreated psychiatric illness).


It has been estimated that half of those for whom medicines are prescribed do not take them in the recommended way. Until recently this was termed "non-compliance", which was sometimes regarded as a manifestation of irrational behavior or willful failure to observe instructions, although forgetfulness is probably a more common reason. But today, health care professionals prefer to talk about "adherence" to a regimen rather than "compliance". The word “adherence” may be preferred by many health care providers, because “compliance” suggests that the patient is passively following the doctor’s orders and that the treatment plan is not based on a therapeutic alliance or contract established between the patient and the physician. According to some, both terms are imperfect and uninformative descriptions of medication-taking behavior.[4]


Causes for poor compliance include:[5]

  • Forgetfulness
  • Prescription not collected or not dispensed
  • Purpose of treatment not clear
  • Perceived lack of effect
  • Real or perceived side-effects
  • Instructions for administering not clear
  • Physical difficulty in complying (e.g. with opening medicine containers, handling small tablets or swallowing difficulties, travel to place of treatment)
  • Unattractive formulation (e.g. unpleasant taste)
  • Complicated regimen
    • Dose frequency[6][7]. The following are a set of estimates of proportion of days compliant[6]:
      • Once daily 84%
      • Twice daily 75%
      • Three times daily 59%
  • Cost of drugs


Non-adherence can be detected by validated questionnaires and by assessing refill records[8][9].

Medication levels may be needed[3].

In hypertension, patients with non-compliance may have a higher white coat effect[3].

Assessment of refill records

When refill records are accessible, many metrics can be calculated. The two most common are[10]:

  • Medication Possession Ratio (MPR): "the sum of the days’ supply for all fills of a given drug in a time period divided by the number of days in the time period"[10]
  • Proportion of Days Covered (PDC) is the same as the MPR but adjusts for days with double coverage of medications due to early refills[10].
    • The PDC is recommended by Medicare[11]the National Quality Forum (NQF)[12]

Providing refill information to health care providers can reduce clinical inertia and improve the quality of prescribing[13].


Available surveys include[14]:

Questions for assessing medication adherence[20]
Question Responses Correlation (r) with viral load[20]
Thinking about the past 4 weeks, what percent of the time were you able to take all your medications as your doctor prescribed them? 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%. −0.352
Thinking about the past 4 weeks, how often did you take all your HIV antiretroviral medications as your doctor prescribed them? None of the time, a little of the time, a good bit of the time, most of the time, all of the time −0.321
Thinking about the past 4 weeks, on average, how would you rate your ability to take all your medications as your doctor prescribed them? Very poor, poor, fair, good, very good, excellent −0.312
Notes: When the first two questions, along with two additional questions are used, sensitivey and specificity for detecting a positive viral load among patients with HIV are about 50% and 70%, respectively.[21]


Interventions to improve adherence have been reviewed[8].


Concordance is an approach at involving the patient in the treatment process to improve compliance and is a current UK NHS initiative.[22] The patient, being informed about the condition and the various treatment options, is jointly involved in the decision as to which course of action to take and partially responsible for the monitoring and reporting back to others involved in their care. Compliance with treatment is improved by:

  • Only recommending treatments that are effective in circumstances when they are required
  • Selecting treatments with lower levels of side effect or concerns for long-term use
  • Prescribing the minimum number of different medications, e.g. prescribing for someone with two concurrent infections a single antibiotic that addresses the sensitivities of both likely bacteria, rather than two separate courses of antibiotics. However, this also raises the spectre of developing antibiotic resistant species in the wider scenario.
  • Simplifying dosage regimen, whether by selecting a different drug or using a sustained release preparations that need less frequent dosages during the day.[23]
  • Explanation of possible side effects and whether important to continue with the course of medication none-the-less.
  • Advice on minimising or otherwise coping with side effects, e.g. advice on whether to take a particular drug on an empty stomach or with food.
  • Developing trust between the patient and their doctor such that patients do not feel they will be embarrassed or seen as ungrateful if they are unable to take a particular drug, thus allowing a better tolerated alternative preparation to be tried.

See also


  1. Sabaté, E. (ed.): "Adherence to Long term Therapies: Evidence for Action". World Health Organization. Geneva, 2003. 212 pp. ISBN 92-4-154599-2. Report 2003
  2. "Patient Compliance with statins" Bandolier Review 2004
  3. 3.0 3.1 3.2 Hamdidouche I, Gosse P, Cremer A, Lorthioir A, Delsart P, Courand PY; et al. (2019). "Clinic Versus Ambulatory Blood Pressure in Resistant Hypertension: Impact of Antihypertensive Medication Nonadherence: A Post Hoc Analysis the DENERHTN Study". Hypertension. 74 (5): 1096–1103. doi:10.1161/HYPERTENSIONAHA.119.13520. PMID 31995406.
  4. Osterberg L, Blaschke T (2005). "Adherence to medication". N Engl J Med. 353 (5): 487–97. doi:10.1056/NEJMra050100. PMID 16079372.
  5. British National Formulary. 45 March 2003.
  6. 6.0 6.1 "Reorganized text". JAMA Otolaryngol Head Neck Surg. 141 (5): 428. 2015. doi:10.1001/jamaoto.2015.0540. PMID 25996397.
  7. Coleman CI, Limone B, Sobieraj DM, Lee S, Roberts MS, Kaur R; et al. (2012). "Dosing frequency and medication adherence in chronic disease". J Manag Care Pharm. 18 (7): 527–39. doi:10.18553/jmcp.2012.18.7.527. PMID 22971206.
  8. 8.0 8.1 Kini V, Ho PM (2018). "Interventions to Improve Medication Adherence: A Review". JAMA. 320 (23): 2461–2473. doi:10.1001/jama.2018.19271. PMID 30561486.
  9. Hamdidouche I, Jullien V, Boutouyrie P, Billaud E, Azizi M, Laurent S (2017). "Drug adherence in hypertension: from methodological issues to cardiovascular outcomes". J Hypertens. 35 (6): 1133–1144. doi:10.1097/HJH.0000000000001299. PMID 28306634.
  10. 10.0 10.1 10.2 Raebel MA, Schmittdiel J, Karter AJ, Konieczny JL, Steiner JF (2013). "Standardizing terminology and definitions of medication adherence and persistence in research employing electronic databases". Med Care. 51 (8 Suppl 3): S11–21. doi:10.1097/MLR.0b013e31829b1d2a. PMC 3727405. PMID 23774515.
  11. : Adherence to Antipsychotic Medications For Individuals with Schizophrenia. Available at
  12. Adherence to Chronic Medications. Available at
  13. Kronish IM, Moise N, McGinn T, Quan Y, Chaplin W, Gallagher BD; et al. (2016). "An Electronic Adherence Measurement Intervention to Reduce Clinical Inertia in the Treatment of Uncontrolled Hypertension: The MATCH Cluster Randomized Clinical Trial". J Gen Intern Med. 31 (11): 1294–1300. doi:10.1007/s11606-016-3757-4. PMC 5071278. PMID 27255750.
  14. Stirratt MJ, Dunbar-Jacob J, Crane HM, Simoni JM, Czajkowski S, Hilliard ME; et al. (2015). "Self-report measures of medication adherence behavior: recommendations on optimal use". Transl Behav Med. 5 (4): 470–82. doi:10.1007/s13142-015-0315-2. PMC 4656225. PMID 26622919.
  15. Available at
  16. Morisky DE, Ang A, Krousel-Wood M, Ward HJ (2008). "Predictive validity of a medication adherence measure in an outpatient setting". J Clin Hypertens (Greenwich). 10 (5): 348–54. doi:10.1111/j.1751-7176.2008.07572.x. PMC 2562622. PMID 18453793.
  17. Byerly MJ, Nakonezny PA, Rush AJ (2008). "The Brief Adherence Rating Scale (BARS) validated against electronic monitoring in assessing the antipsychotic medication adherence of outpatients with schizophrenia and schizoaffective disorder". Schizophr Res. 100 (1–3): 60–9. doi:10.1016/j.schres.2007.12.470. PMID 18255269.
  18. 18.0 18.1 McHorney CA (2009). "The Adherence Estimator: a brief, proximal screener for patient propensity to adhere to prescription medications for chronic disease". Curr Med Res Opin. 25 (1): 215–38. doi:10.1185/03007990802619425. PMID 19210154.
  19. McHorney CA, Victor Spain C, Alexander CM, Simmons J (2009). "Validity of the adherence estimator in the prediction of 9-month persistence with medications prescribed for chronic diseases: a prospective analysis of data from pharmacy claims". Clin Ther. 31 (11): 2584–607. doi:10.1016/j.clinthera.2009.11.030. PMID 20110004.
  20. 20.0 20.1 Berg KM, Wilson IB, Li X, Arnsten JH (2012). "Comparison of antiretroviral adherence questions". AIDS Behav. 16 (2): 461–8. doi:10.1007/s10461-010-9864-z. PMC 3690952. PMID 21181252.
  21. Been SK, Yildiz E, Nieuwkerk PT, Pogány K, van de Vijver DAMC, Verbon A (2017). "Self-reported adherence and pharmacy refill adherence are both predictive for an undetectable viral load among HIV-infected migrants receiving cART". PLoS One. 12 (11): e0186912. doi:10.1371/journal.pone.0186912. PMC 5679639. PMID 29121665.
  22. "Not to be taken as directed - Putting concordance for taking medicines into practice" BMJ. 2003;326:348-349 ( 15 February ) Editorial.
  23. "Dosing and compliance?" Bandolier 117 Nov 2003 Report (see Figure 1)

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