Nonadherence to antipsychotic drugs has been linked to longer duration of inpatient treatment and poorer symptomatic outcome in patients suffering from schizophrenia. In some studies, it has even been identified as the strongest predictor of relapse in patients with a first episode of psychosis.

In this study, researchers aimed to determine whether an inconsistent appearance of antipsychotic drugs dispensed was associated with poorer adherence in patients with schizophrenia.

To conduct this study, we linked information from different administrative healthcare databases from the Basque Country. Patients with a medication possession ratio (<80%) were considered to be nonadherent.

More than a quarter of the study population (26.9%, 1294/4810) was nonadherent to antipsychotics. Different brands of the same antipsychotic were dispensed to 8.5% of the patients. Inconsistent appearance was not associated with nonadherence to antipsychotics. Lower adherence to antipsychotics was associated with several other factors: age ≥65 or <30 years, prescription of typical antipsychotics or of long-acting injectable compounds, and nonadherence to antihypertensive and lipid-lowering drugs

Antipsychotics and lipid-lowering drugs 

The rates of nonadherence to lipid-lowering drugs, antihypertensives, and antidiabetics were lower than that found for antipsychotics. This finding could have several explanations. It might be that these types of drugs are better tolerated by patients than antipsychotics. On the other hand, it could also be that patients on such drugs are precisely those that are most closely monitored through clinical check-ups and hence represent a patient population with better overall adherence.

The lower adherence to typical antipsychotics, which in the market are mainly single-brand products and consequently consistent in appearance, is a finding that underlines that nonadherence does not seem to be attributable to changes in the physical attributes of a drug.

Contrary to the expectations, the researchers did not find a significant association between inconsistent appearance of prescribed antipsychotics and poorer adherence. The percentage of patients who were dispensed different brands of the same antipsychotics was also lower than expected.

The percentage of patients who were prescribed more than 1 antipsychotic during the study period was relatively high, around 40%, a figure comparable to that they found previously in hospitalized patients. Antipsychotic polypharmacy could increase the likelihood of adverse effects, thus causing a poorer adherence.

Further, it could also be argued that more severe patients, who are found to have a lower adherence to treatment, are more often treated with more than 1 drug. The same can be said about the association found between prescription of long-acting injectable antipsychotic and lower adherence rates.

The rates of nonadherence to lipid-lowering drugs, antihypertensives, and antidiabetics were lower than that found for antipsychotics. This finding could have several explanations. It might be that these types of drugs are better tolerated by patients than antipsychotics.

On the other hand, it could also be that patients on such drugs are precisely those that are most closely monitored through clinical check-ups and hence represent a patient population with better overall adherence.

The lower adherence to typical antipsychotics, which in our market are mainly single-brand products and consequently consistent in appearance, is a finding that underlines that nonadherence does not seem to be attributable to changes in the physical attributes of a drug.