Ciclosporin and tacrolimus act by inhibiting the calcium-dependent serine phosphatase, calcineurin. The two drugs are not chemically related, ciclosporin being a cyclic peptide derived from the fungus Tolypocladium inflatum Gamsi, while tacrolimus is a macrolide antibiotic.
Calcineurin is necessary for T cell activation and its inhibition suppresses the early cellular response to antigenic stimuli. There is decreased production of interleukin 2 (IL-2), IL-3 and interferon-gamma.
Side effects
Both drugs are nephrotoxic causing irreversible renal injury with tubular atrophy,
interstitial fibrosis and arteriolar changes.
Hypertension, gingival hypertrophy and hypertrichosis are a particular problem with
ciclosporin while tacrolimus is associated with diabetes mellitus.