Outcomes of acetaminophen infusion on visual analogue scale with varying pain intensity during labour, A randomized controlled trial.

Objective: Acetaminophen (Paracetamol) is the most widely used analgesic. We aimed to determine its efficacy in labour with varying pain intensity, to make labour less painful for women.

Methods: This randomized controlled trial was conducted on primigravida's in their active phase of first stage of labour at Pharmacology department of Army Medical College, National University of Medical Sciences in collaboration with Gynecology department of Pak Emirates Military hospital, Rawalpindi. It was a registered trial with trial number of IRCT20220308054220N1. Duration of study was from May 2022 to October 2022. Patients were divided into two groups, Group-I received two doses of I/V 100 ml normal saline whereas Group-II received I/V two doses of 1000 mg acetaminophen in 100 ml normal saline. Calculated sample size was 130, 65 in each group. Visual analogue scale was used as a tool for data measurement. Data was analysed using split plot anova test.

Results: Mean VAS in acetaminophen infusion group was found to be less than placebo for 1^st dose, but this effect was apparent only one hour after 2^nd dose intervention. The difference in means between groups was statistically significant only for 1^st dose with p-value of 0.003 (for second dose p-value 0.21). In acetaminophen infusion group, for both doses mean VAS decreased as an immediate effect of drug, but then it increased with time. The difference in VAS between intervals had p-value of <0.001 for 1^st dose and 0.005 for 2^nd dose.

Conclusion: Acetaminophen is an effective non opioid labour analgesic in active phase of first stage of labour.