Rationale, aims and objectives: Patient adherence to medication is related to successful pharmacotherapy; however, many patients do not take their medications as prescribed because of poor understanding of their purpose.This study aimed to assess older people’s knowledge of the purpose of drugs prescribed at medical appointments in primary care units and the possible factors related to their level of knowledge about their medications. Method: This was a cross-sectional study conducted in 22 basic health units in Brazil. Older people from this sample who were treated in a primary care setting were interviewed after a consultation with a family practice physician. Data were collected from September 2016 to March 2019. Patients aged ≥ 60 years who visited the primary care units were included in the study (n = 674). Knowledge of prescribed medications was assessed by comparing the responses to the questionnaire and the medication and prescription information. Multivariate analyses were conducted using a Poisson regression with robust variance. Results: The mean age of the sample was 70.1 (standard deviation: ± 7.1) years. Among 674 patients, 272 (40.4%) did not know the indication of at least one of their prescribed drugs; among them 78 (11.6%) did not know the indication of any of their prescribed drugs. In the final multivariate analysis, polypharmacy, illiteracy, and cognitive impairment were found to be associated with misunderstanding the purpose of at least one prescribed drug. Moreover, illiteracy and cognitive impairment were associated with a greater misunderstanding of the purpose of all prescribed drugs. Conclusions: In the studied sample, patients demonstrated a high rate of misunderstanding of the purpose of prescribed drugs. Therefore, it is necessary for health services and professionals to implement strategies that increase the quality of the guidance and instructions given to older people in order to promote adherence to treatment.

Aims: Adherence to prescribed treatment is important for obtaining the desired outcomes in older people care. Polypharmacy is strictly associated with adherence, and complex pharmacotherapy can lead to poor adherence and unexpected outcomes, which are aggravated by older age. The medication regimen complexity index has been proven to be a valid and reliable tool for quantifying the complexity of medication regimens. The objective of the present study was to evaluate the therapeutic complexity of drugs used by older people in a primary care setting in Brazil. Methods: This was a cross-sectional study conducted in 22 basic health units in Brazil. Older people from this sample who were treated in a primary care setting were interviewed after a consultation with a family practice physician. Data were collected from September 2016 to March 2019. Patients aged ≥ 60 years who visited the primary care units were included in the study. Pharmacotherapeutic complexity was assessed according to the medication regimen complexity index. Results: In all, 675 individuals with a mean age of 70 years (±7.1 years) were included. The mean number of drugs prescribed per capita was 2.9 (±1.8). The median medication regimen complexity index for the sample was 8.0, and 26.1% of the patients interviewed had a high medication regimen complexity index. Conclusion: The complexity of the drug regimen was high in almost one-third of the prescriptions analysed. This high complexity might contribute to non-adherence to medication regimens, leading to safety- and effectiveness-related issues. Key words: drug prescriptions, geriatrics, pharmaceutical preparations, polypharmacy, primary health care, older patient.