Pharmacotherapy safety and treatment nonadherence: an ambiguous alliance (data from an outpatient registry)

Aim. To analyze data on adverse drug reactions (ADRs) from medical history and assess pharmacotherapy (PT) adherence among patients within an outpatient registry. This study aims to investigate the relationship between these variables and determine their potential priority.
Material and methods. A cross-sectional study was conducted using data from the “PROFILE” outpatient registry, which included 2,619 patients with cardiovascular diseases (CVD) and associated risk factors from 2014 to 2024. Information on PT adherence and the history of ADRs was collected during physician consultations at the point of registry enrollment and recorded on individualized registration forms. ADR presence was assessed based on whether or not patients reported previous reactions. Patients were classified as adherent if they reported regular use of prescribed medications, partially adherent if they used medications irregularly, and nonadherent if they refused medication entirely. Patients not prescribed PT at the time of registry inclusion were excluded from adherence analysis.
Results. A comparative analysis was conducted between subgroups of patients based on the ADRs presence or absence in their medical histories. At the initial visit, ADRs were reported in 492 (18.8%) patients. Of these, three patients indicated they had not been prescribed pharmacotherapy. Among the remaining 489 patients, 365 (74.6%) were classified as adherent, 31 (6.3%) were nonadherent, and 93 (19.1%) reported irregular adherence. Only 9 (7.3%) out of 124 nonadherent individuals in this subgroup cited ADRs as the reason for their nonadherence.
Among 2,127 patients without ADRs in their medical histories, 36 indicated that PT had not been prescribed. Of the 2,091 remaining individuals, 1,397 (66.8%) were adherent, while adherence issues were identified in 33.2%: 428 (20.5%) refused medication, and 266 (12.7%) took medications irregularly. In this subgroup, only 7 (9.6%) patients attributed their nonadherence to concerns about ADRs. The primary reason for nonadherence in both subgroups was an unwillingness to follow long-term treatment regimens.
Multivariate logistic regression analysis identified five independent variables out of ten that demonstrated statistically significant associations with ADR presence: female sex (OR=1.67; 95% CI: 1.30-2.14; p<0.0001), older age (≥60 years) (OR=1.37; 95% CI: 1.03-1.81; p=0.029), the presence of chronic heart failure (OR=1.66; 95% CI: 1.27-2.17; p<0.0001), polypharmacy (≥5 prescribed medications) (OR=0.74; 95% CI: 0.56-0.98; p=0.037), and complete nonadherence to PT (OR=0.47; 95%CI: 0.29-0.74; p=0.001).
Conclusion. The data from the outpatient registry revealed that nonadherence was more prevalent among patients without documented ADRs in their medical histories compared to those with ADRs (every third patient versus every fourth). ADRs were shown to be a direct cause of nonadherence in less than 10% of cases. Patients who exhibit nonadherence to pharmacotherapy are more likely to have ADRs in their medical histories. Consequently, it appears that adherence takes precedence in the relationship between safety and pharmacotherapy: any deviations from prescribed regimens may lead to increased risks associated with medication use.

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