[A comparison of osteotropic radiopharmaceuticals. II. Plasma clearance of 18F and 99mTc-EHDP (author's transl)].

Renal and extra-renal clearance of 18F and 99mTc-EHDP were compared in the same individuals. The 18F space is twice that of 99mTc-EHDP, as is its renal clearance. 99mTc undergoes glomerular filtration, 18F is excreted by glomerular filtration and tubular secretion. Extraction rate was determined indirectly by a comparison with extra-renal clearance, and for patients without bone disease it was four times as high for 18F as it was for 99mTc-EHDP. In patients with secondary hyperparathyroidism extra-renal clearance is greatly increased. This is explained by an increased extraction rate, which may be different for the two substances.