Drug interactions in the elderly of the Unified Health System (SUS) in Brazil

Background

Elderly people with chronic non-communicable diseases generally use a large amount of medicines, increasing the risk of adverse events that can compromise the quality of pharmacotherapy.

Objective

To analyze the prevalence of drug interactions in the elderly assisted by primary care of the Unified Health System (SUS), who use polypharmacy.

Methods

This is a cross-sectional study, part of the National Survey on Access, Use and Promotion of Rational Use of Medicines (PNAUM) - Services, 2015, which used a representative sample of the Brazilian population. Elderly were considered people with 65 years or older and polypharmacy was defined as the concomitant use of five or more medicines. Drug interactions were classified using Micromedex®. The variables were presented as absolute and relative frequences, mean and standard deviation, using the software Stata® 13.

Results

Of the 1,157 elderly people interviewed, 19.01% (n = 220) were in polypharmacy. The average of chronic diseases was 3.84 ± 1.73 per elderly person, being hypertension (91.82%, n = 202) and arthritis (55.91%, n = 123) he most frequent. There were found 1,076 interactions, ranging from 0 to 23 per person, with an average of 3.87 ± 3.41. In the polypharmacy group, the prevalence of drug interaction was 88.99% (n = 194). Among the interactions, 66.83% (n = 679) were classified as moderate, 31.10% (n = 316) major and 2.07% (n = 21) minor; 84.83% (n = 861) were pharmacodynamic and 15.17% (n = 154) pharmacokinetic. The most prevalent interactions were: Hydrochlorothiazide and Acetylsalicylic Acid (5.31%, n = 54); Captopril and Hydrochlorothiazide (5.31%, n = 54) and Losartan and Acetylsalicylic Acid (3.74%, n = 38).

Conclusions

The most prevalent interactions have synergistic or antagonistic effects, which need monitoring to ensure the safety and effectiveness of treatment, especially due to the physiological changes resulting from aging.

Key messages

Analyze the prevalence of drug interactions in elderly people using polypharmacy. Cross-sectional, evaluative study.