Pharmacokinetics of indium-111 BLEDTA in man

¹¹¹In-BLEDTA is a bleomycin-containing radiopharmaceutical that has proven useful as a tumor imaging agent. Whole blood distribution and pharmacokinetic parameters were studied in nine cancer patients, and the results compared with previously reported studies using ⁵⁷Co-bleomycin. In eight patients studied by bolus intravenous injection, ¹¹¹In-BLEDTA had a beta half-life (t( 1/2 β)) of 1.3 hours, a terminal-phase half-life (t( 1/2 )) of 11.7 hours, a volume of distribution (V(dγ)) of 57.5 L/m², a total body clearance rate (C(1b₂)) of 52.8 ml/min/m², a renal clearance rate (C1(r)) of 23.3 ml/min/m², and a 24-hour urinary excretion of 38.1% total administered dose. ¹¹¹In-BLEDTA and ⁵⁷Co-bleomycin have similar C1(bs) but differing V(ds). Polymorphonuclear cell uptake of ¹¹¹In-BLEDTA may explain its shorter t( 1/2 β) and t( 1/2 ), as well as its lower C1(r) and 24-hour urinary excretion. While the biologic characteristics of ¹¹¹In-BLEDTA contribute to a greater background activity than is observed in scans with ⁵⁷Co-bleomycin, its superior physical properties render it clinically more desirable as a tumor-imaging radiopharmaceutical.