The derivation of the databases and published articles was described in Figure 1. There were 145 studies by searching database. Of them, 121 articles were excluded by screening the title and abstract. The remaining
24 studies concerning the oxycodone for visceral pain after laparoscopic surgery were identified. Among them, 14 studies were excluded due to non-randomized controlled
trials (n=1), ineligible patients (n=2), ineligible comparator (n=9), and absent of eligible outcome reporting (n=2). Therefore, 10 studies [7-16] met our inclusion criteria.
Characteristics of included studies
A total of 815 participants (including 410 oxycodone subjects and 405 controls) matched the inclusion criteria and were selected for the data analysis; study design
and location, characteristics of patients (diagnose, duration of surgery, duration
of anesthesia, ASA (American Society of Anesthesiologists) physical status I/II),
details about interventions and measured outcomes were presented in Table 1.
Results of risk of bias individual studies
Risk of bias of included studies according to the Cochrane Risk of Bias tool was provided
in Figure 2. Of the included 10 studies, seven studies were rated as low risk of bias
on randomization, as they used computer-generated random number sequence. Three studies[8,
9, 14] did not describe the method of randomization. Most studies stated that the
allocation concealment was conducted, however four studies[8, 9, 12, 14] did not report
the information. Only half of the included studies stated that the participants and
personnel were blinded. The other five studies[8, 9, 12-14] did not report the information.
For blinding of outcome assessor, one study stated that partial of the outcome
assessor knew the group assignment during treatment, so it was rated as high risk
of bias on this domain. One study did not report data for some measured outcomes
including nausea, vomiting, or itching, therefore was rated as high risk of selective
Nine studies[7-15] measured pain intensity by VAS or NRS scale. However, only four
of them[8, 10, 12, 13] contributed data for meta-analysis. Result showed that oxycodone can significantly
reduce the pain intensity than other opioids (fentanyl, alfentanil or morphine) in
30 minutes (2 RCTs, N = 218, MD -11.9, 95% CI -16.16 to -7.63), 4 hours (3 RCTs, N
= 290, MD -4.73, 95% CI -8.9 to -0.57), and 24 hours post operation (2 RCTs, N = 208,
MD -3.00, 95% CI -4.02 to -1.98), but not for 48 hours post operation (2 RCTs, N =
208, MD -0.62, 95% CI -3.00 to 1.76) (Figure 3). The data of the other five studies
are not available to do meta-analysis as their data were skewed. Kim 2015 also found a similar results as above. Choi 2018 and Park 2015
concluded that oxycodone and fentanyl have equal effectiveness in relieving postoperative
pain. Choi 2015 found that the pain intensity in oxycodone is significantly lower
than fentanyl group in half hours post operation, but this effect did not last longer
than 0.5 hours. Koch 2008 stated that the intensity of deep abdominal pain was significantly lower in the oxycodone group
at arrival, after 30, 60 and 90 min and at discharge from the PACU.
Four studies[7, 8, 11, 13] reported this outcome. Choi 2015 and Koch 2008 used
the following methods to assess sedation: “S, asleep, easily aroused; 1, awake and alert; 2, occasionally drowsy, easily aroused;
3, frequently drowsy, falls asleep during conversation; 4, somnolent, minimal or no
response to stimulation”. Meta-analysis showed that no difference between oxycodone
and fentanyl for sedation score at 2 (2RCTs, N = 127, RR 2.06, 95% CI 0.56 to 7.60,
Figure 4). Both studies reported that no patient had a sedation score at 3 or 4. Hwang
2014 also concluded that the sedation level was similar between oxycodone and fentanyl
group. However, Lenz 2009 found a different result that sedation level was significantly less in oxycodone group compared with Morphine group (P = 0.006).
All studies reported adverse events. Oxycodone may induce higher risk of dizziness (6 RCTs, N = 455, RR 2.31, 95% CI 1.64 to 3.27) and drowsiness (1 RCT, N = 127, RR 7.88, 95% CI 1.89 to 32.85). There is no difference between groups for the risk of headache, pruritus, respiratory
depression, nausea, and vomiting (Figure 5).
Patient satisfaction was classified into four levels: very satisfied, satisfied, neutral,
dissatisfied. Meta-analysis was performed to assess the number of patients with satisfaction
or very satisfaction in both groups. Result from four studies[8-10, 12] showed that
there are no significant difference between oxycodone versus other opioids for this
outcome (4 RCTs, N = 350, RR 0.88, 95% CI 0.66 to 1.17, Figure 6).