Synergism between oral paracetamol and nefopam in a murine model of postoperative pain

The mechanisms and management of persistent postsurgical pain

An estimated 10%-50% of patients undergoing a surgical intervention will develop persistent postsurgical pain (PPP) lasting more than 3 months despite adequate acute pain management and the availability of minimally invasive procedures. The link between early and late pain outcomes for surgical procedures remains unclear-some patients improve while others develop persistent pain. The elective nature of a surgical procedure offers a unique opportunity for prophylactic or early intervention to prevent the development of PPP and improve our understanding of its associated risk factors, such as pre-operative anxiety and the duration of severe acute postoperative pain. Current perioperative pain management strategies often include opioids, but long-term consumption can lead to tolerance, addiction, opioid-induced hyperalgesia, and death. Pre-clinical models provide the opportunity to dissect mechanisms underpinning the transition from acute to chronic, or persistent, postsurgical pain. This review highlights putative mechanisms of PPP, including sensitisation of peripheral sensory neurons, neuroplasticity in the central nervous system and nociceptive signalling along the neuro-immune axis.

Postoperative analgesia of intraoperative nefopam in patients undergoing anterior cervical spine surgery: A prospective randomized controlled trial

BACKGROUND

Nefopam is a non-opioid, non-nonsteroidal anti-imflammatory drug, analgesic drug that inhibits the reuptake of serotonin, norepinephrine, and dopamine. It is widely used as an adjuvant for pain. This study investigated whether the intraoperative, intravenous infusion of nefopam (20 mg) reduces postoperative morphine consumption, pain scores, and alleviates neuropathic pain in patients undergoing cervical spine surgery.

METHODS

A prospective, paralleled design, randomized study was conducted on 50 patients (aged 18-75 years) in a university-based hospital. The patients were assigned to an intervention or a control group (25 patients in each). The intervention group received a 1-hour infusion of nefopam (20 mg) before the end of surgery. The control group received normal saline (NSS). The outcome measures were morphine consumption during the first 24 postoperative hours, numerical rating scale (NRS) pain scores, and scores for the Thai version of the Neuropathic Pain Symptom Inventory (NPSI-T) in patients with neuropathic pain and adverse drug reactions. The NPSI-T scores were assessed on the preoperative day, postoperative day 1, 3, 15, and 30. The outcome assessors were blinded to group allocation.

RESULTS

Fifty patients were analyzed. During the first 24 postoperative hours, morphine consumption was 8 mg (nefopam) and 12 mg (NSS; P = .130). The intervention and control groups demonstrated no significant differences in the median NRS scores or total NPSI-T scores or adverse drug reactions.

CONCLUSIONS

A single, intraoperative infusion of 20 mg of nefopam did not significantly reduce postoperative (24 hours) morphine consumption in patients undergoing anterior cervical spine surgery.

Paracetamol for multimodal analgesia

Pain and related disability remain a major social and therapeutic problem. Comorbidities and therapies increase drug interactions and side effects making pain management more compounded especially in the elderly who are the fastest-growing pain population. Multimodal analgesia consists of using two or more drugs and/or techniques that target different sites of pain, increasing the level of analgesia and decreasing adverse events from treatment. Paracetamol enhances multimodal analgesia in experimental and clinical pain states. Strong preclinical evidence supports that paracetamol has additive and synergistic interactions with anti-inflammatory, opioid and anti-neuropathic drugs in rodent models of nociceptive and neuropathic pain. Clinical studies in young and adult elderly patients confirm the utility of paracetamol in multimodal, non-opioid or opioid-sparing, therapies for the treatment of acute and chronic pain.