Introduction: Older adults or elderly people over 64 years of age are patients more vulnerable to suffering adverse events related to medication, and this can generate states of both physical and psychological discomfort, loss of autonomy, mental disorders, etc. Objectives: To analyze the drug-drug interaction and inappropriate prescription of drugs in the outpatient setting in the elderly and implement barriers to reduce this problem. Materials and methods: Quasi-experimental study, of the before after type. The Beers 2019 criteria were used to assess inappropriate drug prescribing. The Uptodate definition of drug-drug interactions and their classification were used. Results: 203 polypathological, sarcopenic elderly patients were studied. These patients attended the outpatient consultation during the 2016-2018 period. 99 patients participated in the pre-intervention and 104 in the post-intervention. The distribution by sex was: 110 (54.2%) women and 93 (45.8%) men. The mean age was 77.3 + 13.3 years. In the total sample analyzed before the intervention, 33 (33.3%) showed inappropriate prescription of drugs criteria. Drug interactions in the pre-intervention were present in 51 patients (51.5%). After the intervention that consisted of training doctors with the Beers criteria and editing a list with clinically relevant interactions in the elderly, which can cause adverse events, inappropriate prescription was reduced to 26 patients (25%), p = 0.05, and clinically relevant interactions were reduced from 51 (51.51%) to 12 (11.53%), p = 0.003. The association between inappropriate prescription and clinically relevant interactions is OR: 3.23 (95% CI 1.91-3.88). Conclusions: The proportion of patients with inappropriate prescription is within the ranges published by various authors as well as drug interactions, the intervention was good to reduce the two problems in this sample of patients.