Proglumideis a drug that inhibits gastrointestinal motility and reduces gastric secretions. It acts as a cholecystokinin antagonist, which blocks both the CCKA and CCKB subtypes. It was used mainly in the treatment of stomach ulcers, although it has now been largely replaced by newer drugs for this application. An interesting side effect of proglumide is that it enhances the analgesia produced by opioid drugs, and can prevent or even reverse the development of tolerance to opioid drugs. Proglumide has also been shown to act as a δ-opioid agonist, which may contribute to its analgesic effects. Proglumide also works as a placebo effect amplifier for pain conditions. When injected visibly to a subject, its analgesic effect is bigger than a similarly administered placebo. When injected secretly, it does not have any effect, whereas standard pain drugs have an effect, even if they are administered without the subject's awareness.