In a randomized, controlled trial, patients with joint diseases and concomitant treatment with NSAIDs and diuretics received systematic education. The intervention group was given information focusing on awareness of drug interactions and encouragement of self-adjustment of treatment. Results reveal that the intervention group achieved greater knowledge and that less than one hour of systematic education significantly improved patients' knowledge. (Contains 14 references, 2 tables, and an appendix.) (Author/GCP)