Kikuchi A, et al. - Researchers here measured regional cerebral glucose (energy) consumption and hemodynamic responses in young adults during cognitive tests after antihistamine administration (levocetirizine 5 mg and diphenhydramine 50 mg). Outcomes suggested that in the healthy human brain, physiological “coupling” between metabolism and perfusion might not be maintained under pharmacological influence due to antihistamines. This uncoupling could be caused by a combination of increased energy demands in the prefrontal regions and suppression of vascular permeability in brain capillaries after antihistamine treatment.