α-Fluoromethylhistidine dihydrochloride is a potent irreversible inhibitor of histidine decarboxylase (HDC) and glutathione S-transferase, demonstrating significant potential in studying histidine metabolism and drug metabolism processes. α-Fluoromethylhistidine dihydrochloride offers an effective approach to inhibit enzymes involved in these metabolic pathways. α-Fluoromethylhistidine dihydrochloride has implications for drug development by revealing off-target effects that may influence physiological drug metabolism and elimination mechanisms.