Background <p>Polypharmacy and pharmacokinetic alterations expose elderly patients to an increased risk of iatrogenic events, hospitalisation, and healthcare costs. Therapeutic optimisation is based on identifying potentially inappropriate drug prescriptions (PIDPs) using an explicit approach based on standardised criteria such as STOPP &amp; START and/or an implicit approach. Mobile Geriatric Teams (hereinafter MGT) and clinical pharmacists work together to reduce PIDPs, but pharmacists are not always part of these teams. The PharMoG study included a pharmacist in the MGT (PharMoG team) from a French institution to assess the impact of this collaboration on the acceptance rate of pharmaceutical interventions related to PIDPs.</p> Methods <p>The PharMoG study included elderly patients who were hospitalised. PIDPs were identified before the intervention, at discharge, and three months later using implicit and explicit approaches. The PharMoG team proposed therapeutic optimisation, the acceptance of which by the prescribers was monitored. The analyses used tests suitable for repeated measures and univariate and multivariate models to identify factors associated with acceptance of the proposals. Medication costs were assessed before, at discharge, and three months after the intervention.</p> Results <p>The study included patients with an average age of 87.3 years, and with a Charlson Comorbidity Index score of ≥ 3 in 43.1% of cases. Prior to the intervention, patients were taking an average of 11.3 medicines and had 5.4 identified PIDPs. After the intervention, the average number of medications decreased significantly (<i>p</i> = 0.04), as did the number of PIDPs per patient (<i>p</i> &lt; 0.01), while the proportion of patients exposed to at least one PIDP did not change significantly (<i>p</i> = 0.07). The acceptance rate of the PharMoG team’s proposed treatment optimisations related to PIDPs averaged 65.8% at discharge, with a slight decline three months later. The cost analyses indicate an absence of a significant and robust reduction in prescription costs.</p> Conclusion <p>The PharMoG team’s intervention is associated with a reduction in the number of medicines and PIDPs. These results, although promising, require comparative studies and more comprehensive follow-up to confirm their clinical and economic impact. The study highlights the value of interprofessional cooperation in optimising medication prescriptions for elderly patients, both within hospitals and with community-based professionals.</p> Trial registration <p>NCT04151797 <a href="https://clinicaltrials.gov/study/NCT04151797">https://clinicaltrials.gov/study/NCT04151797</a>.</p>