Metrizamide inhibits human brain hexokinase

The myelographic contrast agent, metrizamide, causes a temporary confusional state in many patients. Since metrizamide is a 2-deoxyglucose analogue, it was tested for inhibitory effects on glucose metabolism. The Michaelis constant (K_m) of human brain hexokinase for glucose rose from 0.039 to 0.24 and 0.47 mM with final metrizamide concentrations of 0,16, and 32 mM, respectively. The maximal velocity did not change. Since metrizamide is injected into the human CSF in concentrations of up to 780 mM, impairment of brain glucose metabolism can be expected. These effects could be largely counteracted if metrizamide were injected in a 100 mM glucose solution.