This study evaluated the effectiveness of pharmaceutical intervention and clinical condition in patients with rheumatoid arthritis (RA) and osteoarthritis (OA) treated at a hospital in Loreto, 2024. Using a pre-experimental, longitudinal, and prospective design with a quantitative approach, a non-probabilistic sample of 50 patients (25 with RA and 25 with OA) was selected. Results showed that 80% of RA patients were single women aged 31 to 50, while 64% of OA patients were married women aged 51 to 70. The most frequent medication-related problems in RA were inappropriate dosage, regimen, and/or duration (16%), non-compliance (16%), and interactions (16%), whereas non-compliance predominated in OA (32%). The most identified negative medication-associated outcome was non-quantitative insecurity, both in RA (28%) and OA (20%). The pharmaceutical intervention showed a statistically significa...