This study investigates the potential benefits of antibiotics and N-acetylcysteine (NAC), a mucolytic agent, in patients who are candidates for endoscopic retrograde cholangiopancreatography (ERCP) due to partial bile duct obstruction. In total, 102 patients who had choledocholithiasis and choledochal dilatations by abdominal ultrasonography were included in the study. The patients were divided into placebo and NAC therapy groups. Physiological saline (equal volume with NAC solution) and ciprofloxacin (2 x 200 mg/d intravenously) were administered to the placebo group, and NAC (1800 mg/d intravenously) and ciprofloxacin (2 x 200 mg/d intravenously) were administered to the NAC group. In both groups, treatment protocols were administered for 7 days before ERCP. Total and direct bilirubin, aspartate aminotransferase (AST), alanine aminotransferase (ALT), C-reactive protein (CRP), alkaline phosphatase (ALP), gamma-glutamyl transpeptidase (GGT), white blood cell (WBC) count, and neutrophil percent (NE%) levels were measured before the 7-day treatment protocol. The same measurements were also evaluated before ERCP. In the NAC group, the levels of ALP, GGT, WBC, CRP, and NE% decreased significantly (P < .001), whereas a significant decrease did not occur in the placebo group. The combined usage of NAC and ciprofloxacin can be an alternative therapeutic option until ERCP is performed in partial cholestatic patients.