<prompt> Mechanism of action tacrolimus is ?Inhibition of calcineurinAntimetabolitemTOR inhibitorInhibition of DNA synthesis  <response>: Ans. is a i.e., Inhibition of calcineurin Tacrolimus It is a macrolide immunosuppressant agent. Its mechanism of action is similar to cyclosporine, i.e. inhibition of transcription of IL-2 and T-cell proliferation, but it binds to other immunophilin called FKBP in contrast to cyclosporine which binds to cyclophilin. Subsequent steps are some, i.e. inhibition of calcineurin, which inhibits T cell activation. Tocrolimus is 10-100 times more potent than cyclosporine. It is also more toxic than cyclosporin. Adverse effects are nephrotoxicity most common, neurotoxicity, hyperglycemia DM. Mechanism of nephrotoxicity - Periglomerular afferent aeriolar vasoconstrication and reduced GFR. 