On all ten treatment days, patients on both the ketamine and placebo groups are placed on the cardiac monitor for cardiac rhythm, blood pressure, pulse and oxygen saturation monitoring. In addition, Clonidine (0.1 mg, po) and Versed (4 mg, iv) will be administered. Clonidine has been shown, in animals, to potentiate the neuropathic pain-relieving action of NMDA receptor blockers like ketamine while preventing their neurotoxic side effects. Versed at this dose, provides mild sedation and relieves anxiety.