Pain
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Randomized Controlled Trial
Results from Clinical Trials of a Selective Ionotropic Glutamate Receptor 5 (iGluR5) Antagonist, LY5454694 Tosylate, in 2 Chronic Pain Conditions.
This article reports results of 2 studies investigating LY545694 in pain due to osteoarthritis (OA) of the knee and diabetic peripheral neuropathic pain (DPNP). Study I randomized patients to either of 2 doses of LY545694 or to placebo, and study II randomized patients to either of 3 doses of LY545694, to pregabalin, or to placebo. No significant differences between LY545694 groups and placebo were observed on the primary (average pain severity) or secondary efficacy measures in either study. ⋯ Without an active control, it is unknown whether the OA study was negative or failed. Consequently, efficacy of selective ionotropic glutamate receptor antagonism in chronic pain conditions may warrant further investigation. Future trials should consider different pain conditions, contain a positive control with larger patient numbers per arm, and be conducted within a single region.
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Randomized Controlled Trial
Partial reinforcement, extinction, and placebo analgesia.
Numerous studies indicate that placebo analgesia can be established via conditioning procedures. However, these studies have exclusively involved conditioning under continuous reinforcement. Thus, it is currently unknown whether placebo analgesia can be established under partial reinforcement and how durable any such effect would be. ⋯ However, although the placebo analgesia established under CRF extinguished during test phase, the placebo analgesia established under PRF did not. These findings indicate that PRF can induce placebo analgesia and that these effects are more resistant to extinction than those established via CRF. PRF may therefore reflect a novel way of enhancing clinical outcomes via the placebo effect.