REDUCED RENAL FRACTIONAL EXCRETION OF LITHIUM IN CYSTIC-FIBROSIS

We hypothesized that patients with cystic fibrosis would have abnormal lithium handling because the genetic defect in cystic fibrosis encode s an ion channel which causes a generalized electrolyte transport diso rder in epithelial membranes. Eight patients with cystic fibrosis and eight age-sex matched healthy subjects ingested 600 mg lithium carbona te and had urine and serum lithium levels assessed 24 h later. Compare d with healthy subjects, the patients with cystic fibrosis had higher serum lithium levels (0.071 +/- 0.038 vs 0.113 +/- 0.055 mmol l(-1), P = 0.03) and had lower fractional renal excretion of lithium (27.5 +/- 14.8 vs 18.8 +/- 9.3%, P = 0.03). Caution should be used in prescribi ng standard doses of lithium to patients with cystic fibrosis until mo re definitive data are available.