The prevalence of polypharmacy is high in patients with chronic kidney disease (CKD), and polypharmacy is associated with problems such as increased risk of adverse drug events, medication errors, and poor medication adherence. It is also higher in patients undergoing dialysis or kidney transplantation compared to patients with CKD 3-5, and hyper-polypharmacy (taking 10 or more drugs) is said to be associated with a higher risk of all-cause mortality, decreased renal function, and decreased quality of life.

We investigated the relationship between the number of concomitant medications and renal prognosis at 12 months after surgery in recipients who underwent living donor kidney transplantation at our hospital between January 2014 and August 2023. Concomitant medications were defined as normal (N group: 5 or less medications), polypharmacy (P group: 6-9 medications), and hyper-polypharmacy (HP group: 10 or more medications) based on the number of medications.

The median number of medications in all 78 patients was 8 (1-18), 8 (5-20), and 8 (3-16) before transplantation, 3 months after surgery, and 12 months after surgery, respectively, with no significant difference. There was no consistent trend in the proportions of N group and P group, but the number of HP group patients decreased to 27, 24, and 23 before transplantation, 3 months after surgery, and 12 months after surgery. When all medication types were examined, no differences were observed in the engraftment rate or renal function. When examining the number of medications excluding immunosuppressants, patients taking fewer medications (six or fewer) had significantly better renal function 3 and 12 months after surgery compared with patients taking more medications (seven or more) (p = 0.039 and 0.041, respectively).

The proportion of patients requiring multiple medications (10 or more) after kidney transplantation was gradually decreasing. A smaller number of medications excluding immunosuppressants after kidney transplantation was associated with better renal function.