Intra-individual comparison of 3(R)-BMIPP and 3(S)-BMIPP isomers in humans

The racemic 15-(p-iodophenyl)-3(R,S)-methylpentadecanoic acid (BMIPP) is currently used at several centers for myocardial metabolic imaging with SPECT. Recently, the 3(R)-BMIPP isomer showed a 20%-25% higher myocardial uptake and lower liver uptake than 3(S)-BMIPP in fasted rats. The aim of this study was to determine if these differences in myocardial and liver uptake also occur in humans. Methods: Iodine-123-labeled 3(R)-BMIPP and 3(S)-BMIPP isomers were injected at rest, on two separate days, in six patients with stable coronary artery disease. Dual-head, whole-body scintigraphy was performed 20 min and 3 hr after injection. SPECT cardiac imaging was performed 60 min after injection. Results: Myocardial activity averaged (% injected dose ± s.d.) 3.15 ± 0.49 versus 3.01 ± 0.44 at 20 min (p = ns) and 2.64 ± 0.38 versus 2.55 ± 0.41 at 3 hr postinjection (p = ns) for the 3(R)-BMIPP and 3(S)-BMIPP isomers, respectively. Liver activity averaged 9.50 ± 1.18 versus 9.44 ± 0.66 at 20 min and 5.33 ± 0.64 versus 5.43 ± 0.66 at 3 hr, respectively (p = ns). SPECT showed no difference in the distribution of the two isomers between normal and infarcted myocardium. Conclusion: There is no significant difference in myocardial and liver distribution of the 3(R)-BMIPP and 3(S)-BMIPP isomers in humans.