<h3>Background:</h3> Few interventions have proven effective in reducing the overuse of antibiotics for acute respiratory infections. We evaluated the effect of DECISION+2, a shared decision-making training program, on the percentage of patients who decided to take antibiotics after consultation with a physician or resident. <h3>Methods:</h3> We performed a randomized trial, clustered at the level of family practice teaching unit, with 2 study arms: DECISION+2 and control. The DECISION+2 training program included a 2-hour online tutorial followed by a 2-hour interactive seminar about shared decision-making. The primary outcome was the proportion of patients who decided to use antibiotics immediately after consultation. We also recorded patients' perception that shared decision-making had occurred. Two weeks after the initial consultation, we assessed patients' adherence to the decision, repeat consultation, decisional regret and quality of life. <h3>Results:</h3> We compared outcomes among 181 patients who consulted 77 physicians in 5 family practice teaching units in the DECISION+2 group, and 178 patients who consulted 72 physicians in 4 family practice teaching units in the control group. The percentage of patients who decided to use antibiotics after consultation was 52.2% in the control group and 27.2% in the DECISION+2 group (absolute difference 25.0%, adjusted relative risk 0.48, 95% confidence interval 0.34–0.68). DECISION+2 was associated with patients taking a more active role in decision-making (<i>Z</i> = 3.9, <i>p</i> < 0.001). Patient outcomes 2 weeks after consultation were similar in both groups. <h3>Interpretation:</h3> The shared decision-making program DECISION+2 enhanced patient participation in decision-making and led to fewer patients deciding to use antibiotics for acute respiratory infections. This reduction did not have a negative effect on patient outcomes 2 weeks after consultation. ClinicalTrials.gov trial register no. NCT01116076.
