The aim of this study was to examine whether thioxanthine-type antipsychotics (chlorprothixene and cis(z)-flupenthixol) and phenothiazine-type antipsychotics (chlorpromazine and fluphenazine) produced spinal anesthesia. Using a rat model of intrathecal injection, we evaluated spinal anesthesia of antipsychotic drugs (chlorprothixene, cis(z)-flupenthixol, chlorpromazine, and fluphenazine) and bupivacaine, a known local anesthetic. At a same dose of 2.31μmol/kg, chlorprothixene had the most potent spinal blockades (P<0.001) and the longest duration of action (P<0.001) of motor function and nociception among those antipsychotic drugs. On the 50% effective dose (ED 50 ) basis, the ranks of potencies were chlorprothixene=bupivacaine>cis(z)-flupenthixol>chlorpromazine>fluphenazine (P<0.01 for the differences) in dose–response studies. At an equianesthetic basis (ED 25 , ED 50 , and ED 75 ), the spinal block duration caused by chlorprothixene, cis(z)-flupenthixol, chlorpromazine or fluphenazine was longer than that caused by bupivacaine (P<0.05). These results showed that chlorprothixene produced a similar potency and longer duration of spinal anesthesia than did bupivacaine, whereas several other antipsychotics produced less potency than did bupivacaine.