Improved competitive inhibitors of FAAH employ an α-keto heterocyclic pharmacophore and a binding subunit having a ?-unsaturation. The α-keto heterocyclic pharmacophore and a binding subunit are attached to one another, preferably by a hydrocarbon chain. The improvement lies in the use of a heterocyclic pharmacophore selected from oxazoles, oxadiazoles, thiazoles, and thiadiazoles that have alkyl or aryl substituents at their 4 and/or 5 positions. The improved competitive inhibitors of FAAH display enhanced activity over conventional competitive inhibitors of FAAH.