Calcineurin Inhibitors and Uric Acid Control in Solid Organ Transplantation: A Systematic Review

: Background/Objectives: Asymptomatic hyperuricemia has been associated with increased cardiovascular risk; it is related to factors such as diet, genetic predisposition, and drug-related side effects. Impairment of uric acid control has been associated with the calcineurin inhibitors cyclosporin and tacrolimus, although available studies did not reach the same conclusions. Their widespread use in solid organ transplantation potentially exposes this population to higher cardiovascular risk. This systematic review aimed to assess their role in hyperuricemia risk compared with other immunosuppressive treatments and to clarify potential differences between cyclosporin and tacrolimus. Methods: The search was conducted in MEDLINE and Embase, limited to adult subjects, using the following terms: ((cyclosporin) OR (cyclosporine) OR (tacrolimus) OR (calcineurin inhibitor)) AND ((uric acid) OR (urate) OR (hyperuricemia)) AND ((transplant) OR (transplantation)). We assessed the quality of the studies according to the Critical Appraisal Skills Programme checklist. Results: After screening 639 manuscripts, we selected 36 studies that were relevant to our focus: 28 evaluated kidney transplant patients, while only eight focused on other solid organ transplants. Specifically, 20 studies compared calcineurin inhibitors with other immunosuppressants, while 15 assessed the impact of cyclosporin versus tacrolimus, and one study contributed to both scenarios. The prevalence of hyperuricemia ranged from 30 to 80% among patients receiving calcineurin inhibitors, with a slightly higher prevalence with cyclosporin than with tacrolimus (51-61% vs. 36-42%, respectively). The overall quality of the included studies was generally rated as low to moderate, with only ten studies focusing on uric acid control. Conclusions: Given the heterogeneity and overall quality of the available studies, no definitive conclusions can be drawn. In particular, the comparative effect of cyclosporin and tacrolimus remains uncertain because of conflicting findings across studies. Although calcineurin inhibitors may adversely affect uric acid control in transplant recipients, this association may be influenced by several confounding factors.