Comparison of the Effect of Melatonin, Dexmedetomidine, and Gabapentin on Reduction of Postoperative Pain and Anxiety Following Laminectomy

A Randomized Clinical Trial

Reza Jouybar; Somayeh Kazemifar; Naeimehossadat Asmarian; Ali Karami; Saeed Khademi


BMC Anesthesiol. 2022;22(318) 

In This Article

Abstract and Introduction


Background: This study aimed to compare the effects of melatonin, dexmedetomidine, and gabapentin on postoperative pain and anxiety following laminectomy.

Methods: In this randomized clinical trial, 99 patients aged 40–60 years old with American Society of Anesthesiologists physical status I-II undergoing laminectomy were divided into three groups receiving 600mg gabapentin (group G), 10mg melatonin (group M), or starch tablets (group D). The Hospital Anxiety and Depression Scale (HADS) was used to measure postoperative anxiety while a Visual Analogue Scale (VAS) was employed to measure pain severity. Patients' satisfaction with pain treatment was also measured together with the frequency of nausea and vomiting.

Results: The postoperative HADS decreased in all groups over time. Time and group had no significant interaction effect on the HADS score. Patients in the melatonin group had lower HADS at 2 and 6h after surgery. According to the VAS, the groups significantly differed in pain scores 6 and 24h after surgery. Lower VAS scores were observed 6h after surgery in the dexmedetomidine group compared with the gabapentin group and 24h after surgery in the dexmedetomidine group compared with the gabapentin and melatonin groups. Narcotic requirements, patients' satisfaction, and vital sign changes did not significantly vary among the groups. Notably, patients in the melatonin group had less nausea and vomiting.

Trial Registration: This study was registered in the Iranian Registry of Clinical Trials (No. IRCT20141009019470N82, 29.06.2019) where the trial protocol could be accessed.

Conclusion: Melatonin is effective as a postoperative anti-anxiety drug. Dexmedetomidine is useful in reducing postoperative pain.


Spinal procedures are associated with intense pain in the postoperative period, mostly in the first few days after surgery. Effective pain management leads to improved functional outcomes, early discharge, early ambulation, and prevention of chronic pain.[1] The activation of various pain mechanisms such as nociceptive, neuropathic, and inflammatory pathways may result in postoperative pain.[2] Back pain originates from diverse tissues such as vertebrae, ligaments, nerve root sleeves, dura, facet joint capsules, fascia, intervertebral discs, and muscles. Various nociceptors and mechanoreceptors are capable of stimulating pain transmission. Back pain is mostly localized in subjects when the referred pain persists in the postoperative period.[3] The intensity of postoperative pain is directly related to the number of vertebrae involved in the surgery.[4] The site of the surgery does not seem to have any effect on pain severity, which remains similar across lumbar spine, thoracic, and cervical operations.[5,6]

Various medications such as morphine (delivered by an intravenous patient-controlled analgesia pump), fentanyl (continuous injection through an epidural catheter), N-methyl-D-aspartate (NMDA) receptor antagonists, corticosteroids, nonsteroidal anti-inflammatory drugs (NSAIDs), clonidine, capsaicin, and tapentadol are used to relieve post-laminectomy pain. The mechanism of each of the above drugs is different and they have several side effects such as nausea, vomiting, platelet dysfunction, hemorrhage, gastric ulceration, renal toxicity, and respiratory depression.[1,7–9]

Dexmedetomidine is a selective α2 adrenergic receptor agonist that is metabolized in the liver and is primarily excreted via the kidneys. Dexmedetomidine facilitates arousable sedation with no effect on the respiratory drive; it also reduces the need for inhaled anesthetics. However, due to hemodynamic changes, the drug should be used carefully for conscious sedation (CS), monitored anesthetic care (MAC), or general anesthesia..[9–14] Despite being an imidazole compound, dexmedetomidine possesses analgesic effects and minimizes postoperative opioid consumption as well as nausea, vomiting, and anxiety.[15,16]

Melatonin is mainly secreted from the pineal gland by the suprachiasmatic nucleus. This neurohormone possesses a circadian secretion pattern and regulates the biological clock; it also offers antiemetic, analgesic, and anxiolytic effects. Due to its effect on both acute and chronic pain, melatonin fulfills a beneficial role in reducing postoperative opioid consumption while minimizing nausea and vomiting. In addition, melatonin can be used to moderate the effect of light on the autonomic system.[15,17–20]

Several studies have reported that melatonin, as an analgesic, anti-inflammatory, anxiolytic, and anti-agitation premedication, is associated with sedation and anxiolysis without adverse effects on recall and driving performance. Furthermore, some studies have found confirmed the effects of melatonin on pain and anxiety, though a consensus is yet to be reached in this regard.[21,22]

Gabapentin is an anticonvulsant drug classified under the category of gabapentinoids, which are prescribed for diabetic and post-herpetic neuralgia (PHN) patients. Preemptive use of gabapentin reduces the severity of postoperative pain, thereby minimizing the use of analgesics such as narcotics. On the other hand, gabapentin reduces postoperative stress, anxiety, nausea, and vomiting. The amount of anesthetic required for general anesthesia is also reduced when gabapentin is administered.[18,23–25]

Based on the mentioned data, the present study aimed to compare the effects of melatonin, dexmedetomidine, and gabapentin on post-laminectomy pain, and anxiety.