A negative correlation between hyperalgesia and analgesia in patients with chronic radicular pain: Is hydromorphone therapy a double-edged sword?

Background: opioids are the cornerstone therapy for the treatment of moderate to severe pain. yet,unconfirmed evidence suggests that chronic exposure to opioids may cause hypersensitivity to pain,a phenomenon known as opioid-induced hyperalgesia (oih). objectives: the current preliminary prospective study was aimed to explore the relationship between experimental oih and clinical opioid induced analgesia (oia) in a model of experimental oih in patients with chronic radicular pain using intermediate-term opioid therapy. study design: prospective evaluation setting: interdisciplinary pain clinic at a referral health care campus methods: thirty patients with chronic neuropathic (radicular) pain were assessed prior to and following 4 weeks of an individually titrated dose of oral hydromorphone treatment (4-20 mg/d). the assessments included an evaluation of experimental oih by testing for heat pain intensity and cold pain tolerance and an assessment of oia by completing pain and disability questionnaires. results: hydromorphone was found to induce hyperalgesia,as measured by an elevation of phasic heat pain intensity (p < 0.05). at the same time,hydromorphone caused significant clinical analgesic effects. there was a notable reduction in average daily pain scores (primary analgesic outcome) of 26 visual analog scale (0-100) points. a significant negative correlation was found between oih and all oia measures (r = -0.389,p < 0.05 for the primary analgesic outcome). hydromorphone dosage was positively correlated with oih (p < 0.01,r = 0.467) and negatively correlated with oia parameters (r = -0.592,p < 0.01 for the primary analgesia outcome). limitations: the nonrandomized,open-label,prospective evaluation. conclusion: a 4-week regimen of open-label hydromorphone therapy results in a dosedependent oih,which negatively correlates with its analgesic effect. future randomized,controlled,and blinded studies are needed to verify these preliminary results.