Radiolabeling the neuroactive compound ibogaine with technetium-99m tricarbonyl produced a tracer that entered the mouse brain poorly, at a rate similar to other tracers known to have low brain uptake. The brain entry rate was about 70 times lower than that of a standard clinical brain-imaging agent. Neither the labeled ibogaine nor the tricarbonyl core alone were substrates for the main efflux transporters at the blood-brain barrier. Instead, the limited brain penetration was attributed to the compound's lipophilicity and its interaction with the membrane's positive dipole potential, as lowering that potential with phloretin increased transport roughly threefold. The findings indicate that ibogaine directly labeled with this radionuclide is unsuitable for central nervous system imaging.
Ketamine oral solutions at 10 mg/mL and 50 mg/mL, prepared in a flavored suspending excipient and stored in amber plastic bottles, remain chemically stable for at least 90 days at both refrigeration (2°C-8°C) and ambient (22°C-25°C) temperatures. Over 90 days, at least 98% of the initial ketamine concentration was retained under all conditions tested. Solution pH, color, and odor also remained unchanged throughout the study period. These results indicate that extemporaneously compounded oral ketamine solutions can be stored for up to 90 days without significant degradation.