Tacrolimus combined with everolimus versus sirolimus in organ transplantation: a comparative pharmacovigilance analysis of the FDA Adverse Event Reporting System.

To compare the adverse event reporting profiles of tacrolimus combined with everolimus versus tacrolimus combined with sirolimus for immunosuppressive therapy after organ transplantation using the FDA Adverse Event Reporting System (FAERS) database and to generate hypotheses to inform the individualized selection of mTOR inhibitors. As FAERS does not record drug dose, the two combinations are compared without reference to tacrolimus dosing. Adverse event reports from the FAERS database spanning the first quarter of 2004 to the fourth quarter of 2025 were extracted. Disproportionality analysis was performed using four methods: reporting odds ratio (ROR), proportional reporting ratio (PRR), Bayesian confidence propagation neural network (BCPNN), and empirical Bayesian geometric mean (EBGM). Analyses were conducted at the system organ class (SOC) and preferred term (PT) levels, as well as age-stratified (< 60 years vs. ≥ 60 years), sex-stratified, and time-to-onset analyses. A total of 3101 reports for tacrolimus combined with everolimus (ta_ev) involving 13,237 adverse events, and 3093 reports for tacrolimus combined with sirolimus (ta_si) involving 13,356 adverse events were retrieved. The ta_ev regimen generated 459 PT signals covering 25 SOCs, with the three strongest SOCs being renal and urinary disorders (ROR = 4.85), infections and infestations (ROR = 3.55), and blood and lymphatic system disorders (ROR = 3.48). The ta_si regimen generated 413 PT signals also covering 25 SOCs, with the three strongest SOCs being immune system disorders (ROR = 5.22), renal and urinary disorders (ROR = 3.52), and blood and lymphatic system disorders (ROR = 2.98). Both regimens generated strong renal/urinary and haematological disproportionality signals, but the reporting patterns diverged in several respects: the ta_ev regimen had a significantly stronger signal for hepatobiliary disorders (ROR = 3.12 vs. 1.89), whereas the ta_si regimen showed a stronger signal for cardiac disorders (ROR = 1.14 vs. 0.81) and a stronger association with wound healing complications. A formal between-regimen comparison (ratio of reporting odds ratios (rROR), with 95% CIs) indicated that these differences in reporting were statistically distinguishable (Table 5), although the magnitudes were modest for the cardiac and several other classes. Age-stratified analysis indicated that patients under 60 years of age had a higher frequency and greater variety of adverse events; male patients accounted for a higher proportion of reports in both groups. The median time to adverse event onset was approximately 3-3.5 months, but more than 10% of events occurred after one year of treatment. Tacrolimus combined with everolimus and with sirolimus show distinct adverse event reporting profiles in FAERS: the everolimus-based combination was relatively enriched for hepatobiliary, BK-related renal and infectious events, and the sirolimus-based combination for cardiac, immune system, and wound healing events. These disproportionality signals describe reporting rather than measured risk and are hypothesis-generating; they require confirmation in controlled studies before they can guide the individualized choice of an mTOR inhibitor, with closer monitoring suggested for recipients under 60 years of age and for male patients.