Authors, Year, Country	Study Design	Population, Injury Treated	Intervention, Dosage	Main Findings
Bang et al., 2010[@283422] USA	Randomized controlled trial	46 patients Arthroscopic rotator cuff repair	Gabapentin (n=23) 300 mg 2 h before surgery	VAS scores at 2, 6, and 12 h postoperatively were significantly lower in the gabapentin group than the placebo group (p=0.023, p=0.019, and p=0.022, respectively). Consumption of fentanyl over 24 h and the incidence of side effects was similar between the groups.
Panah Khahi et al., 2011[@283423] Singapore	Randomized controlled trial	64 patients Internal fixation of tibia	Gabapentin (n=32) 300 mg 2 h before surgery	Pain scores were significantly lower in the gabapentin group at 2 h post-surgery compared to placebo (p=0.004). However, scores at 12 and 24 h post-surgery were not significantly different between the two groups.
Pandey et al., 2005[@283424] India	Randomized controlled trial	100 patients Single-level lumbar discectomy	Gabapentin (n=20) 300, 600, 900, or 1200 mg 2 h before surgery	Patients who received gabapentin 300 mg had significantly lower VAS score at all time points. They consumed less fentanyl (987.5±129.6 μg) compared to placebo (1217.5±182.0 μg; p< 0.05). Those who received gabapentin 600, 900, and 1200 mg had lower VAS scores at all time points than those who received gabapentin 300 mg (p< 0.05). Increasing gabapentin dosage from 600 to 1200 mg did not decrease the VAS score, or significantly decrease fentanyl consumption (702.5, 635, and 626.5 μg).
Pandey et al., 2004[@283425] India	Randomized controlled trial	56 patients Lumbar discoidectomy	Gabapentin (n=28) 300 mg 2 h before surgery	Patients in the gabapentin group had significantly lower VAS scores at all time intervals of 0-6, 6-12, 12-18, and 18-24 h than those in the placebo group (3.5±2.3, 3.2±2.1, 1.8±1.7, 1.2±1.3 vs 6.1±1.7, 4.4±1.2, 3.3±1.1, 2.1±1.2; p< 0.05). The total fentanyl consumed after surgery in the first 24 h in the gabapentin group (233.5±141.9) was significantly less than in the placebo group (359.6±104.1; p<0.05).
Turan et al., 2006[@283426] Turkey	Prospective	40 patients Lower extremity surgery	Gabapentin (n= 20) 1.2 g 1 day before and for 2 days after surgery	Pain scores at 1, 4, 8, 12, and 16 h (p<0.001), PCEA bolus requirements at 24, 48, and 72 h (p<0.05), and paracetamol consumption (p<0.05), were significantly lower in the gabapentin group compared to the placebo group. Patient satisfaction with post-operative pain management at 24 h was also better in the gabapentin group (p<0.001). However, incidence of dizziness was higher in the gabapentin group (35% vs. 5%; p<0.05).
Ménigaux et al., 2005[@283427] France	Randomized controlled trial	40 patients Arthroscopic anterior cruciate ligament repair	Gabapentin (n=20) 1200 mg 1-2 h before surgery	Patients treated with gabapentin required less morphine than the control group (29±22 mg vs. 69±40 mg, respectively; p<0.001). VAS pain scores at rest and after mobilization were significantly reduced in the gabapentin group. Pre-medication with gabapentin also improved pre-operative anxiolysis and early knee mobilization at 24 and 48 h post-operatively.
Wang et al., 2018[@283428] China	Randomized controlled trial	45 pediatric patients Prevention of phantom limb pain (PLP) following lower limb amputation	Gabapentin (n= 23) 300 mg on day 1, 600 mg on day 2, and 900 mg from day 3 to day 30 after surgery	Acute post-operative pain intensity in gabapentin group was significantly lower than the placebo group p<0.05). The rate of PLP at the last follow-up was lower in the gabapentin group (43.48%) compared to placebo (77.27%, p=0.033).
Hah et al., 2018[@283429]	Randomized controlled trial	422 patients Mixed Surgical Cohort	Gabapentin (n= 208) 1200 mg before surgery and 1800 mg for 72 hours after	Patients treated with gabapentin had a 24% increase in the rate of opioid cessation after surgery (p=0.05). However, there were no significant differences in the number of adverse events.
Gordh et al., 2008[@283430] Sweden	Randomized controlled trial	98 patients Neuropathic pain caused by traumatic or post-surgical peripheral nerve injury	Gabapentin (n=50) 300 mg increased stepwise until reaching total pain relief or a max. dose of 2400 mg	Compared with placebo, gabapentin provided significantly better pain relief (p=0.015), more patients had at least a 30% pain reduction (p=0.040), and the pain interfered with patients sleep significantly less (p=0.0016).
Dolgun,[@283431] 2014 Turkey	Randomized controlled trial	54 patients Acute neuropathic pain after lumbar discoidectomy	Gabapentin (n=27) and Pregabalin (n=27) 300 mg gabapentin on day 1, 600 mg on day 2, and 900 mg on day 3 with maintenance of 900-1800 mg TID 150 mg pregabalin increased to 300 mg after 1 week, up to 300 mg BID or 200 mg TID	Both treatment groups pain improved according to the LANSS scale. Gabapentin scores decreased from 14 to 10 points 6 months after surgery and to 4 points at 1 year (p<0.001). Pregabalin scores decreased from 16 to 12 at 6 months post-op and further decreased to 5 at 1-year post-op (both p<0·001). Oswestry disability index (ODI) and VAS scores also significantly improved in both groups (p<0·001).
Khurana et al., 2014[@283432] India	Randomized controlled trial	90 patients Lumbar discectomy	Gabapentin and Pregabalin (n= 30 each) 300 mg gabapentin or 75 mg pregabalin 1 hour before surgery and 8 hourly for 7 days thereafter	Compared to placebo, patients receiving gabapentin and pregabalin had significantly reduced static and dynamic pain intensity and required significantly less doses of rescue drugs post-operatively. The pregabalin group had significantly improved Prolo scores and Oswestry Disability Index scores at all time intervals compared to placebo. Pregabalin had more pronounced clinical effect compared to gabapentin (not statistically significant until 21 days).
Kheirabadiet al., 2020[@283434] Iran	Randomized controlled trial	120 patients Lower extremity surgery	Pregabalin (n=30) and Gabapentin (n=30) 300 mg gabapentin or 75 mg pregabalin 1 h before surgery	There was a significant reduction in pain severity only at the first-time point between pregabalin and placebo treated patients (p=0.014). The pregabalin group required lower doses of opioids during admission. There was no significant difference in pain reduction, opioid administration, and side effects between the pregabalin, gabapentin, and celecoxib groups.
Altiparmak et al., 2018[@283436] USA	Randomized controlled trial	94 patients Spinal surgery	Duloxetine (n=31) and Pregabalin (n=30) 60 mg duloxetine or 75 mg 1 h before surgery and 12 and 24 h after	In all groups, there was a significant reduction in mean post-op Montreal Cognitive Assessment (MoCA) scores with the highest reduction in the pregabalin group (1.83±1.31 point), then the duloxetine group (1.16±0.82). The least decrease was in the control group (0.49±0.61). The mean VAS scores of the pregabalin and duloxetine groups were similar throughout the study and were significantly lower than the control group.
Attia and Monsour, 2017[@283437] Egypt	Randomized controlled trial	120 patients Lumbar laminectomy	Duloxetine (n=30) 60 mg duloxetine or 60 mg duloxetine with etoricoxib 120 mg 1 h before surgery and 24 h after	Duloxetine and etoricoxib alone did not affect pain scores with movement, yet their combination allowed for a significant reduction over the post-operative period at rest and with movement. At rest, Etoricoxib showed a significant decrease in pain at all times when compared to placebo, and at 0, 2 and 4 h when compared with the Duloxetine group. Duloxetine alone only showed a significant decrease in pain at 24 h and 48 h when compared with placebo. Morphine requirement after 24 h were significantly lower in the combination group but both Duloxetine and etoricoxib alone showed a significant decrease.
Kim et al., 2021[@283438]	Retrospective	239 patients Total knee arthroplasty	Duloxetine (n=137) 30 mg for 6 weeks after surgery	There was no significant difference in pain VAS score, WOMAC Pain and Function score between the duloxetine and opioid treated groups at each time point between before and after surgery (all p>0.05).
Li et al., 2021[@283435] USA	Randomized controlled trial	96 patients Total Hip Arthroplasty	Duloxetine (n=48) 60 mg daily from 2 days before surgery to 14 days after	Patients administered duloxetine had significantly lower pain severity scores upon movement and performed better in terms of resting pain (3 weeks after surgery), morphine requirements, and satisfaction level at discharge compared to placebo (all p<0.05).
Ho et al., 2010[@283439]	Randomized controlled trial	47 patients Total knee arthroplasty	Duloxetine (n=23) 60 mg 2 h before and one day after surgery	In the duloxetine group, morphine requirements were significantly lower throughout the first 48 h following surgery compared to placebo (p=0.017). However, there were no statistically significant differences in pain score or adverse effects between the groups.
YaDeau et al., 2016[@283440] USA	Randomized controlled trial	106 patients Total knee arthroplasty	Duloxetine (n=53) 60 mg 30 min before surgery until 14 days after	Total opioid use was significantly reduced in the duloxetine group from the day of surgery through three months post-op (p=0.002). Nausea severity was also significantly reduced in the duloxetine group on the first day post-op. Fourteen days post-op, duloxetine did not reduce pain scores at rest, with ambulation, and with flexion compared to placebo.
Bedin et al., 2016[@283441] Brazil	Randomized controlled trial	57 Patients Lumbar spinal fusion	Duloxetine (n=28) 60 mg 1 h before surgery and once the following morning	At 24 and 48 hours post-operatively, fentanyl consumption was significantly lower in the duloxetine group compared to placebo (p<0.001 and p<0.000, respectively). Pain scores did not significantly differ between groups during this time.