Gd-HP-DO3A in clinical MR imaging of the brain. As part of a phase II clinical trial, 14 patients with presumed intracranial neoplastic disease underwent magnetic resonance (MR) imaging before and after intravenous injection of gadolinium 1,4,7-tris(carboxymethyl)-10-(2'-hydroxypropyl)-1,4,7,10-tetraazacycl ododecane (HP-DO3A). This neutral (nonionic) gadolinium chelate has lower osmolality, when formulated at equimolar concentrations, and superior in vitro stability compared with gadopentetate dimeglumine. The safety profile of Gd-HP-DO3A permitted administration of doses up to 0.3 mmol/kg, three times the dose of gadopentetate dimeglumine approved by the U.S. Food and Drug Administration. In this limited clinical trial, Gd-HP-DO3A proved to be a safe and efficacious agent in MR imaging of the head. The only change documented in patient monitoring was that of slight skin redness at the injection site immediately after administration in two patients. No statistically significant changes due to administration of the agent were noted in laboratory evaluations. These results differ from those obtained with gadopentetate, which induces a transient rise in serum iron and bilirubin levels in up to 26% of patients. Administration of higher doses of Gd-HP-DO3A, either 0.2 or 0.3 mmol/kg, appeared to provide improved enhancement. No decrease in efficacy at these high doses was noted. 