<prompt> Mechanism of action tacrolimus is -Inhibition of calcineurinAntimetabolitemTOR inhibitorInhibition of DNA synthesis  <response>: Ans. is a i.e., Inhibition of calcineurin Tacrolimuso It is a macrolide immunosuppressant agent.o 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 immunophiiin called FKBP in contrast to cyclosporine which binds to cyclophilin. Subsequent steps are some, i.e. inhibition of calcineurin, which inhibits T cell activation,o Tocrolimus is 10-100 times more potent than cyclosporine,o It is also more toxic than cyclosporin.o Adverse effects are nephrotoxicity most common, neurotoxicity, hyperglycemia DM.Mechanism of nephrotoxicity - Perigiomerular afferent arteriolar vasoconstrication and reduced GFR. 