This study was carried out on 240 pregnant women undergoing cesarean section. The results showed that since postoperative pain was a very common complication, especially in cesarean section, preoperative administration of intravenous paracetamol could have a significant analgesic effect, reduce the required meperidine after surgery. This result was obtained through measurement of postoperative pain in patients using VAS and the amount of post-cesarean meperidine administrations.
In the present study, paracetamol was administered as preemptive. The purpose of this method was to block pain receptors before painful stimulation. In Ong et al. and Arici et al. studies, paracetamol was administered in the same manner (9, 11).
Most studies have emphasized the analgesic effects of paracetamol. Kiliçaslan et al. compared the patients’ post-cesarean pain score in two groups (n=25), one receiving intravenous paracetamol plus tramadol and one receiving tramadol alone. They concluded that pain score was lower in paracetamol group (19). Inal conducted a study on 50 patients under cesarean surgery and compared the analgesic effect of paracetamol and meperidine. They found that paracetamol led to reduction of pain score in the patients (20). Faize and colleagues were compared intravenous paracetamol and ketamine injection to control pain after abdominal hysterectomy. Pain score (VAS) was significantly lower in the paracetamol group, the highest difference being seen at 6 hours after surgery (21). This result is in agreement with the results of the present study. In another study, Ali and Khan compared the analgesic impact of tramadol plus paracetamol and tramadol alone on 60 patients undergoing laparoscopic surgery and they obtained the same results as presented above (22). Cattabriga et al. investigated the analgesic effect of paracetamol on postoperative pain in patients undergoing cardiac surgery and reported that intravenous paracetamol could induce appropriate analgesic effect in the patients (23). In all studies cited above, the frequency of administration and total dose of narcotic analgesic were reduced when paracetamol was administered. In our study, although the difference between the two groups was not statistically significant for meperidine intake, but clinically, meperidine administration was lower in the paracetamol group.
Vuilleumier et al. conducted a study in Switzerland in 1998 and compared the postoperative analgesic effect of paracetamol and morphine. They found that paracetamol could be used as a substitute to morphine to induce postoperative analgesia in moderate pain. They reported that morphine had a better short-term analgesic effect, but finally paracetamol had a longer analgesic effect (24). Nikoda et al. carried out a study in Russia in 2002 and examined the postoperative analgesic effects of Paracetamol on 30 patients. They concluded that paracetamol reduce the severity of postoperative pain (25). In another study, Emir et al. compared the analgesic effect of tramadol plus paracetamol and tramadol alone on the spinal surgery and reported a higher efficacy of paracetamol (26). Mofidi et al. also conducted a study on 80 patients with renal pain and found that intravenous paracetamol to be a safe and effective drug with no remarkable side effects in relieving pain in renal patients. Further, they reported paracetamol had a higher efficacy and fewer complications than tramadol in relieving the patients’ renal pain (27).
In the present study, paracetamol was administered preoperatively and, although peak efficacy was 1 hour and duration of effect was 4 to 6 hours, pain score was significantly reduced at 6 and 24 hours postoperatively. In Arici et al. study, the effect of preoperative and end-of-operation injections of paracetamol was compared with the control group in abdominal hysterectomy. There was a significant difference between the pain scores of the two intervention groups and the control group. Although the difference of pain score was not significant in the two intervention groups, it was clinically lower in the preemptive group than in the other group, and this effect remained for up to 24 hours. Morphine consumption was lower in the intervention groups than in the control group. The difference between the two intervention groups was statistically significant, Preoperative use was lower than the end-operative group (11). In this study, as our study, the analgesic effect of paracetamol was longer than the drug effect duration. Maybe these results caused by pain receptors blocking before painful stimulations. In addition, cutting off pain signals can prevent central nerves from becoming sensitive.
However, some studies have shown no significant difference between the analgesic effect of paracetamol and narcotic analgesics, such as the study of Van Aken et al. that compared the analgesic effects of paracetamol and morphine in dental surgery (28) and that of Rawal et al. which compared the analgesic effect of oral tramadol and intravenous paracetamol in outpatient surgeries (29). The differences between the results of these two studies with our and other results appear to be due to differences in the extent of surgery. However, in both of these articles, paracetamol had no weaker effect than the other two drugs.
In our study, the side effects such as nausea and chills were reported in both groups. Previous studies have mostly reported significantly fewer side effects in paracetamol group, due to reduced total dose of narcotic drug (30, 31).
Pain had a descending trend in both groups during the study period, which is in agreement with patient’s gradual improvement and reduction of neural damages. Generally, pain level was different in both groups; pain reduction was greater in paracetamol group, this difference is statistically significant at 6 and 24 Hours after operation . This result is similar to some studies, such as Sinatra et al. study (2005) that investigated the effect and safety of single and repeated administration of 1g intravenous paracetamol for pain management following large orthopedic surgery (32), study of Olonisakin et al. (2012) on the saving effect of intravenous paracetamol on using morphine for postoperative pain control in women (31) and study of Iqbal (2009) on the analgesic level and quality of postoperative intravenous administration of paracetamol and reduction of narcotic requirement (33).
However, some studies like that of Uysal et al. (2011) on comparative analysis of efficacy of intravenous paracetamol versus tramadol for postoperative analgesia in pediatric adenotonsillectomy (34), study of Kiliçaslan et al. (2010) on the effect of intravenous paracetamol on postoperative analgesia and tramadol on cesarean section (19) and that of Lee et al. (2010) on the effect of paracetamol, ketorolac and paracetamol plus morphine on pain control after thyroidectomy showed no significant difference between the two groups in terms of pain reduction, the only advantage being quicker rehabilitation (35).
The present study found nausea and chills in both paracetamol and control groups although no significant difference was observed. Sanjar Mousavi and Khalili reported dizziness, nausea, headache, vomiting, sleepiness and immobility in both groups receiving paracetamol and opioid for postoperative pain relief, but no significant difference was observed between groups (36).
The findings of the present study indicated no significant difference between the two groups in systolic blood pressure in different measurement stages, during and after cesarean, but diastolic blood pressure 15 minutes after start of cesarean section was significantly lower in paracetamol group than control group. Further, diastolic blood pressure 45 minutes after starting of cesarean, was significantly lower in paracetamol group than control group. In a systematic review by Turtle et al. (2012), it was shown that in many studies paracetamol increased blood pressure, but in two studies, no effect was observed, and in one study, hypotension with paracetamol was observed. Therefore, they concluded that the effect of paracetamol on blood pressure was unclear (37). Based on the results of Beyzaee et al., systolic blood pressure changes in both groups underwent significant changes over time, reducing three hours after surgery and then rising again, but no significant difference was found between paracetamol and control groups with respect to systolic blood pressure. Similarly, their results showed significant changes in diastolic blood pressure over time in both groups, but the difference between two groups was not statistically significant (38). According to the results of the present study and the above mentioned studies, further studies on the effect of paracetamol on blood pressure seems to be needed.
Since the effects of a drug have been studied in this study and the drugs have specific pharmacogenetic effects, so the results of this study can be extended to other races and communities.