Effect of cyclosporin on serum creatinine in patients with rheumatoid arthritis.

Serum creatinine levels were measured before, during and after the administration of cyclosporin (Cy) in a double-blind placebo-controlled study in patients with rheumatoid arthritis (RA). The level rose significantly during and after Cy therapy, whereas the initial serum creatinine value did not change in the placebo group. The increase in the Cy group was not correlated with the mean Cy blood level. The rise in serum creatinine during Cy therapy was gradual and was not significantly correlated with the initial creatinine level; relative to the pretreatment value, the post-treatment increase was significantly correlated with the increase during Cy therapy. It is concluded that Cy administration for not more than 6 months, and at a maximum dosage of 10 mg/kg for 2 months, leads to an irreversible loss of more than 10% of renal function in RA patients. The damage may be ascribed to the combination of Cy with other factors compromising the kidneys, e.g., the use of non-steroidal anti-inflammatory drugs in the potentially systemic disorder of RA.