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 significantly induce anesthetic effect, reduce the required pethidine after surgery and prevent its harmful effects such as respiratory dysfunctions, maternal nausea and neonatal sleepiness. This result was obtained through measurement of pain in patients using VAS and number of post-cesarean pethidine administrations.
Most studies have emphasized the anesthetic 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 (17). 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 (18). 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 (19). 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 (20). In all studies cited above, the frequency of administration and total dose of narcotic analgesic were reduced when paracetamol was administered.
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 (21) and that of Rawal et al. which compared the analgesic effect of oral tramadol and intravenous paracetamol in outpatient surgeries (22).
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 (23). 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 (24). 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 (25). 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 remawrkable 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 (26).
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 (27, 28).
Studies have used various scales for pain evaluation (27–29). With respect to pain measurement scale, we used VAS, and it is different from most other studies (1). However, some studies like that of Olonisakin et al. (2012) in Nigeria, which evaluated the saving efficacy of intravenous paracetamol in using morphine for postoperative pain in women, had used the same scale (28). Yet, this difference did not affect the results.
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. Further, pain during administration was significantly lower in all four administrations in paracetamol group. Moreover, this difference in pain level was not observed in both groups 1 and 2 hours after administration, and patients in both groups experienced a similar pain. Hence, it can be concluded that intravenous paracetamol has had a longer efficacy, causing persistent pain relief and significant difference in pain level in both groups until next administration. Generally, pain level was different in both groups; pain reduction was greater in paracetamol group, this difference is statistically significant. 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 1 g intravenous paracetamol for pain management following large orthopedic surgery (30), study of Olonisakin et al. (2012) on the saving effect of intravenous paracetamol on using morphine for postoperative pain control in women (28) and study of Iqbal (2009) on the analgesic level and quality of postoperative intravenous administration of paracetamol and reduction of narcotic requirement (31).
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 (32), study of Kiliçaslan et al. (2010) on the effect of intravenous paracetamol on postoperative analgesia and tramadol on cesarean Sect. (17) 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 (33).
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 (34).
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 cesarean was significantly lower in paracetamol group than control group. Since blood pressure drop is not a common side effect of paracetamol administration, it can be concluded that paracetamol prevents increase of blood pressure increase by relieving pain in patients. 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 (35).
Unrelieved postoperative pain can lead to complications such as nausea, vomiting, hypertension, increased heart rate, myocardial ischemia, pulmonary atelectasis, hypoxia, dyspnea, coughing, decreased respiratory volume, urinary retention, increased coagulation and thrombosis, immunosuppression, anxiety, insomnia, central sensitization and chronic pain. Thus, specialists have always tried to find out appropriate and low-risk techniques to eliminate or reduce pain in patients.
For a long time, opioids drugs were the main choice for postoperative pain relief, but they are used less due to adverse effects such as respiratory depression, nausea, vomiting, slow gastrointestinal function and reduced consciousness, which delays rehabilitation and movement. Nowadays, various methods have been suggested for decreasing opioids use, one of which is use of non-narcotic drugs along with or as a substitute to narcotic drugs. Recently, paracetamol, which is an analgesic and antipyretic medication, is administered intravenously before, during and after surgery. Use of this drug before surgical has shown favorable effects in different studies (36), which is in line with the results of the current study. Numerous studies have been done on the efficacy of this pain relief method, which have mainly indicated adequate analgesia, lower sleepiness, less side effects, accelerated rehabilitation and reduced use of opiates after surgery.
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.