ciclosporin, also spelled cyclosporine and cyclosporin, is a calcineurin inhibitor, used as an immunosuppressant medication. it is a natural product. it is taken by mouth or by injection into a vein for rheumatoid arthritis, psoriasis, crohn's disease, nephrotic syndrome, and in organ transplants to prevent rejection. it is also used as eye drops for keratoconjunctivitis sicca (dry eyes). 
 
common side effects include high blood pressure, headache, kidney problems, increased hair growth, and vomiting. other severe side effects include an increased risk of infection, liver problems, and an increased risk of lymphoma. blood levels of the medication should be checked to decrease the risk of side effects. use during pregnancy may result in preterm birth; however, ciclosporin does not appear to cause birth defects. 
 
ciclosporin is believed to work by decreasing the function of lymphocytes. it does this by forming a complex with cyclophilin to block the phosphatase activity of calcineurin, which in turn decreases the production of inflammatory cytokines by t-lymphocytes. 
 
ciclosporin was isolated in 1971 from the fungus tolypocladium inflatum and came into medical use in 1983. it is on the world health organization's list of essential medicines, the safest and most effective medicines needed in a health system. in 2017, it was the 248th most commonly prescribed medication in the united states, with more than one million prescriptions that year. 
 
medical uses 
ciclosporin is approved by the fda to treat and prevent graft-versus-host disease in bone marrow transplantation and to prevent rejection of kidney, heart, and liver transplants. it is also approved in the us for treating of rheumatoid arthritis and psoriasis, persistent nummular keratitis following adenoviral keratoconjunctivitis, and as eye drops for treating dry eyes caused by sj?gren's syndrome and meibomian gland dysfunction. 
 
in addition to these indications, ciclosporin is also used in severe atopic dermatitis, kimura disease, pyoderma gangrenosum, chronic hives, acute systemic mastocytosis, and posterior or intermediate uveitis with noninfective cause.[citation needed] it is also used, albeit infrequently, in severe rheumatoid arthritis and related diseases.[citation needed] 
 
ciclosporin has also been used in people with acute severe ulcerative colitis and hives that do not respond to treatment with steroids.