Mental Illness Pharmaceuticals

Patient adherence to antipsychotic medications

Patients with schizophrenia often require medication—such as antipsychotics—to control the symptoms of their disease. However, adherence to these medications has been poor. Valenstein et al. (2004) estimate that 40% of patients are non-compliant with therapy [i.e., mediation possession ratio (MPR)<0.8].

Why are schizophrenia patients likely to be non-complient to antipsychotic therapy?

One key reason is side effects. Extrapyramidal symptoms, postural hypotension, sedation, anticholinergic side effects and weight gain are all common side effects. Additionally, patients may become non-adherent if their copays are significant. Others may not have insight into their disease and may believe that the medications are unnecessary.

Who is likely to be non-compliant?

A study by Higashi et al. (2013) found that patients who lacked insight into their disease, and who were substance abusers were less likely to be adherent. Unsurprisingly, patients who have been adherent to their medications in the past are more likely to be adherent to their medications in the future. Patients who believe ex ante that the medication was unlikely to be effective were less likely to be adherent.   In fact, Gibson et al. (2013) found that 54% reported intentional non-adherence and 29% of patients who were non-adherent were “satisfied with being so.” As some of the antipsychotics produce lethargy, patients may miss does when they want an energy boost. One patient stated “I had a meeting at work the next day so skipped my evening dose.”

A study by Valenstein et al. (2004) found that patients who are younger or African American are less likely to be compliant. Higashi et al. (2013), however, notes that other studies do not show any relationship between sociodemographic factors and adherence. Further, patients who receive a high dose therapy may be non-compliant. The causation between non-adherence and high dose therapy is unclear. Non-adherence may increase the likelihood of a high dose; if patients are non-adherent, therapy will be ineffective and physicians may try to address this lack of effectiveness by increasing the dose. Alternatively, increasing the dose may increase side effects that may lead patients to discontinue therapy. Patients on atypical antipsychotics may have better adherence. Valenstein et al. (2004) found that overall adherence rates were similar between patients who use conventional and atypical therapies; however, patients who use atypicals may represent more serious cases. The authors found that patients who switch from conventional antipsychotics to atypicals improve adherence whereas those who switch from atypicals to conventional antipsychotics experience a decrease in adherence.

Do patients report adherence information to doctors accurately?

Sometimes yes, sometimes no. Gibson (2013) reports that one patient stated “I told the Dr the symptoms but wasn’t honest about what medication I was taking less of.” Some patients don’t report non-adherence for fear they will be taken off the medication or they feel ashamed.

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