Abstract OBJECTIVES In patients with deep sternal wound infection (DSWI), primary closure of the sternal bone over high negative pressure Redon drains has shown to be a safe and feasible treatment method. Addition of local gentamicin could accelerate healing and improve clinical outcomes. METHODS We conducted a randomized controlled trial to evaluate the effectiveness of local gentamicin in the treatment of DSWI. In the treatment group, collagenous carriers containing gentamicin were left between the sternal halves during sternal refixation. In the control group, no local antibiotics were used. Primary outcome was hospital stay. Secondary outcomes were mortality, reoperation, wound sterilization time, time till removal of all drains and duration of intravenous antibiotic treatment. RESULTS Forty-one patients were included in the trial of which 20 were allocated to the treatment group. Baseline characteristics were similar in both groups. Drains could be removed after a median of 8.5 days in the treatment group and 14.5 days in the control group (P-value: 0.343). Intravenous antibiotics were administered for a median of 23.5 days in the treatment group and 38.5 days in the control group (P-value: 0.343). The median hospital stay was 27 days in the treatment group and 28 days in the control group (P-value: 0.873). Mortality rate was 10% in the treatment group and 9.5% in the control group (P-value: 0,959). No side effects were observed. CONCLUSIONS This randomized controlled trial showed that addition of local gentamicin in the treatment of DSWI did not result in shorter length of stay. Clinical trial registration number 2014-001170-33.