Spinal analgesics.

The important issues to be emphasized when considering the intrathecal administration of novel analgesics are their proven antinociceptive effect, safety (short- and long-term effects on the spinal cord and potential toxicities), stability in shelf solution and at body temperature by itself, or in combination with other drugs in spinal fluid, compatibility with a long-term spinal infusion pump, whether they are of sufficiently high potency and solubility to be used in the finite volume of an implanted infusion pump, and if a pharmaceutical company is willing to invest the immense resources needed for US Food and Drug Administration approval and subsequent commercial development.