Cyclosporin A levels in suction-blister fluid of patients with psoriasis treated systemically

Oral cyclosporin A (CyA) is highly effective in the treatment of psoriasis. The long-term use is limited by dose-dependent side-effects, and the local concentration of CyA is a determining factor in treatment. The concentration of CyA in suction-blister fluid (SBF) and in whole blood was assessed using a polyclonal radioimmunoassay (RIA). This was carried out in patients with psoriasis following a single dose of CyA and while on adequate oral treatment with the drug. Peak blister fluid levels ranged from 32 to 170 ng/ml, and whole blood levels from 1250 to 2540 ng/ml. CyA trough levels (12 h following taking the drug) in the blister fluid ranged from 22 to 113 ng/ml, and in whole blood from 148 to 935 ng/ml. The trough concentrations in SBF were approximately 10% of whole blood trough levels