Dose-Dependent Preventive Analgesic Effects of Intravenous Dexamethasone versus Paracetamol after Cesarean Section under Spinal Anesthesia: A Randomized Triple-Blind Controlled Trial

Abstract

Background: Effective management of post-cesarean pain remains an important clinical challenge. Both glucocorticoids and paracetamol are used as preventive analgesics, but the optimal dose of dexamethasone and its comparative efficacy versus paracetamol are not well established. This study evaluated the preventive analgesic effects of three intravenous dexamethasone doses (2, 4, and 6 mg) compared with intravenous paracetamol and placebo on somatic and visceral pain after elective cesarean section under spinal anesthesia.
Methods: In this randomized triple-blind controlled trial, 235 women (ASA II, aged 18–45 years) undergoing elective cesarean section were allocated to five groups: dexamethasone 2 mg (Dexa 2, n=42), dexamethasone 4 mg (Dexa 4, n=50), dexamethasone 6 mg (Dexa 6, n=43), paracetamol 1 g (PARA, n=49), and control (Control, n=51). All patients received spinal anesthesia with 2.5 mL hyperbaric bupivacaine 0.5%. Somatic pain (VAS 0–10) was assessed at 2, 4, and 6 hours postoperatively, and visceral pain (during uterine massage) at 2 and 6 hours. Rescue analgesia (meperidine 25 mg) was administered when VAS exceeded 3. Analgesic requirement, spinal block onset time, and peak sensory level were recorded. Multiple linear regression was performed to identify predictors of pain at 6 hours.
Results: Baseline characteristics were comparable between groups except for gravidity (p=0.002). At 2 hours, somatic pain was lowest in the Dexa 4 (2.32±0.62) and Dexa 6 (2.20±0.63) groups, both significantly lower than control (3.86±0.93), paracetamol (3.36±0.56), and Dexa 2 (2.80±0.80) (all p<0.001). At 4 hours, Dexa 4 showed higher somatic pain (5.14±0.80) than Dexa 2 (4.02±0.81), Dexa 6 (4.09±0.92), and paracetamol (3.95±1.05) (all p<0.001) and was comparable to control (4.86±0.89). No significant differences were observed at 6 hours (p=0.251). Visceral pain at 2 hours was lowest in the Dexa 2 group (5.0±0.93), significantly lower than Dexa 4 (5.74±0.75) and paracetamol (6.0±0.81), while the control group had the highest scores (8.23±0.61) (all p<0.001). By 6 hours, visceral pain scores were similar across groups (p=0.995). Rescue analgesia at 2 hours was required in 0% (Dexa 6), 2% (Dexa 4), 23.8% (Dexa 2), 32.7% (paracetamol), and 68.6% (control). At 4 hours, the proportions were 90.5%, 70.0%, 93.0%, 69.4%, and 90.2%, respectively. Dexa 4 demonstrated the fastest spinal block onset (24.06±1.05 s, p<0.001). Regression analysis showed that in the Dexa 2 group, higher gestational age predicted lower visceral pain at 6 hours (β=−0.10, p=0.044), while in the Dexa 4 group, higher maternal age (β=0.061, p=0.005) and BMI (β=0.064, p=0.008) predicted higher visceral pain.
Conclusion: Preoperative dexamethasone and paracetamol both improved early postoperative analgesia after cesarean section under spinal anesthesia. Dexamethasone 6 mg provided the greatest reduction in early somatic pain and analgesic requirement, whereas dexamethasone 2 mg showed a more favorable effect on early visceral pain. The observed variability in analgesic response across doses suggests a complex dose and time-dependent effect of dexamethasone, warranting further investigation.