Tacrine hydrochloride hydrate is an inhibitor of both acetyl (AChE) and butyryl-cholinestrase (BChE) with IC₅₀s of 31 nM and 25.6 nM, respectively. IC50 & Target: IC50: 31 nM (AChE), 25.6 nM (BChE) In Vitro: Tacrine hydrochloride hydrate (12.5 to 37.5 nM) inhibits venom acetylcholinesterase as well as human serum butyrylcholinesterase in a concentration-dependent manner. The IC₅₀ is 31 nM for snake venom AChE and 25.6 nM for human BChE^[1]. In Vivo: Pretreatment with Tacrine hydrochloride hydrate also modifies absolute levels of cocaine self-administration during reacquisition. Body weight declines approximately one-half percent over four days of treatment with intravenous Tacrine hydrochloride hydrate. Delivery of Tacrine hydrochloride hydrate by osmotic pump does not alter either linear- or repeated- cocaine-induced locomotor activity. There is no significant main effect or interaction with Tacrine hydrochloride hydrate treatment on active lever responding during reinstatement. Post hoc comparisons indicate that rats self-administering cocaine has significantly lower alkaline phosphatase levels, relative to Tacrine hydrochloride hydrate- but not saline- treated rats evaluated by conditioned-place preference^[2].