The two calcineurin inhibitors routinely used for kidney transplant immunosuppression are cyclosporine (CSA) and tacrolimus (TAC). Their mechanism of action is somewhat similar (they both inhibit calcineurin, which under normal circumstances induces transcription of IL-2 in lymphocytes) but they get there by different routes: CSA binds cyclophilin, and the CSA:cyclophilin complex inhibits calcineurin, whereas TAC binds FK506-binding protein 1a (FKBP1a), and the TAC-FKBP1a complex also inhibits calcineurin.
CSA and TAC have an overlapping side effect profile, the specifics of which lend themselves quite nicely to standardized testing...
Both CSA & TAC can cause nephrotoxicity, tremor, headache, thrombotic microangiopathy, hyperlipidemia, hypomagnesemia, and hyperkalemia.
CSA in particular causes excessive hair growth and gum hyperplasia.
TAC in particular causes hair loss and has a higher rate of NODAT (new-onset diabetes mellitus after transplant).