Background The most common side effect of spinal opioid administration is pruritus, which
has been treated with a variety of agents with variable success. Currently, there are few
animal models developed to study this side effect. The aim of this study was to establish a
nonhuman primate model to pharmacologically characterize the effects of intrathecal
administration of morphine. Methods Eight adult rhesus monkeys were used. Scratching
responses were videotaped and counted by observers who were blinded to experimental …