A Compound of formula (wherein X is O or S and R1-R5 are disclosed herein) or a pharmaceutically acceptable salt thereof (each being a “Piperazine Compound”), pharmaceutical compositions comprising a Piperazine Compound and methods for treating or preventing pain, UI, an ulcer, IBD, IBS, an addictive disorder, Parkinson's disease, parkinsonism, anxiety, epilepsy, stroke, a seizure, a pruritic condition, psychosis, a cognitive disorder, a memory deficit, restricted brain function, Huntington's chorea, amyotrophic lateral sclerosis, dementia, retinopathy, a muscle spasm, a migraine, vomiting, dyskinesia, or depression in an animal comprising administering to an animal in need thereof an effective amount of a Piperazine Compound are disclosed.