Background/Aims: Elobixibat, an ileal bile acid transporter (apical sodium-dependent bile acid transporter) inhibitor, was recently launched in Japan for the treatment of chronic idiopathic constipation. We conducted an interim analysis of post-marketing surveillance to evaluate the safety and efficacy of elobixibat in elderly patients with chronic constipation and compared the efficacy according to administration time. Methods: Safety and efficacy outcomes were evaluated through patient interviews for 4 weeks. Results: Adverse drug reactions (ADRs) were observed in 5.24% of the 1049 patients analyzed; diarrhea (2.19%) and abdominal pain (1.81%) were the most common. A serious ADR of death was reported in one patient (0.10%). The incidence of ADRs in the ≥ 65-year old or ≥ 75-year-old subpopulation was similar to that in the total patient population. Mean bowel movements per week significantly increased from 2.9 ± 2.5 at baseline to 5.0 ± 3.1 (P< 0.001) at Week 2 and 5.3 ± 2.6 (P < 0.001) at Week 4. The mean Bristol Stool Form Scale score significantly increased from 2.3 ± 1.4 at baseline to 3.8 ± 1.3 (P < 0.001) at Week 2 and 3.9 ± 1.1 at Week 4 (P < 0.001). Bowel movements significantly increased in the elderly population and subpopulations receiving elobixibat before breakfast, lunch, or dinner. The median time to bowel movement was 5 hours. Conclusion The results suggested that elobixibat was well-tolerated and efficacious in elderly patients with chronic constipation and can be administered before any meals.