Background The use of potentially inappropriate medication (PIMs) is frequent in nursing homes (NHs), and leads to worsened health outcomes for their residents. Numerous initiatives to curb their use have been launched. Most studies of PIMs use in NHs, however, focused on their prevalence, and provide few insights on the evolution of their use. Objective The objective of this analysis is to measure the evolution of PIMs use in the nursing NHs of western Switzerland taking part in an integrated pharmacy service (IPS). Methods Drug consumption data from 166 NHs were collected for 2014 to 2018, through the monitoring of the IPS. These data were cross-referenced with validated PIMs lists (Beers' list and Norwegian General Practice-Nursing Home, NORGEP-NH) to compute the number of potentially inappropriate defined daily doses per average resident (DDD/res) in each NH. Linear mixed-effects models were used to assess the evolution of PIMs use over time, following the NORGEP-NH classification of PIMs and the drug classes involved. Results In 2018, the number of DDD/res was 7.3 (SD 1.9); of those, 2.2 (SD 0.8) were potentially inappropriate. Psycholeptics, psychoanaleptics and antihypertenseives were the most-used PIMs. Between 2014 and 2018, the number of potentially inappropriate DDD/res decreased by 0.03 per year (CI95 [−0.05; −0.01]). Conclusions This study complements others that focused on the prevalence of PIMs use in NHs. The statistically significant reduction in the use of PIMs is an encouraging sign, but is probably not clinically meaningful for NH residents. With the growing concerns of the potential harms of these drugs, more specific interventions and implementation strategies need to be developed to help clinicians further reduce their use in NHs.