Ms. S, age 53, has bipolar disorder, dyslipidemia, and drug-induced tremor and presents to the clinic complaining of increasing depressive symptoms despite a history of response to her current medication regimen (Table 1). When informed that her lithium and divalproex levels are subtherapeutic, Ms. S admits that she doesn’t always take her medication. She understands her psychiatric and medical conditions and rationale for her current medications; however, she recently changed jobs, which has affected her ability to adhere to her regimen. Ms. S says the only thing preventing her from adhering to her medication is the frequency of administration.
Only approximately one-half of patients with chronic illness adhere to their medication regimen.1 Nonadherence has been reported in 20% to 72% of patients with schizophrenia, 20% to 50% of those with bipolar disorder, and 28% to 52% with major depressive disorder.2 Medication nonadherence can impact a patient’s health outcomes1 and could lead to increased hospitalizations, homelessness, substance use, decreased quality of life, and suicide; however, it is difficult to fully determine the extent of medication nonadherence due to lack of standard measurement methodology.2
Factors that affect medication adherence in patients with psychiatric diagnoses include:
- patient-related (ie, demographic factors)
- psychological (eg, lack of insight into illness, negative emotions toward medications)
- social and environmental (eg, therapeutic alliance with the physician, housing stability and support, and discharge planning)
- medication-related (eg, complex dosing schedule).2
Medication regimen tolerability, complexity, and cost; patient understanding of medication indications and onset of therapeutic effect; and patient’s view of benefits can impact adherence.1,3 Assessing medication adherence and identifying barriers specific to the patient is essential when developing a treatment plan. If complexity is a barrier, simplify the medication regimen.
Claxton et al4 found an inverse relationship between medication dosing and adherence. Reviewing data from 76 studies that used electronic monitoring (records the time and date of actual dosing events) the overall rate of medication adherence was 71% ± 17%. Adherence rates were significantly higher with once daily (79% ± 14%) vs 3 times daily (65% ± 16%) or 4 times daily (51% ± 20%), and twice daily (69% ± 15%) was significantly better than 4 times daily dosing. Adherence between once daily and twice daily or twice daily and 3 times daily did not result in a significant difference. The authors noted that electronic monitoring has limitations; patients could have opened the medication bottle but not ingested the drug.4