Purpose Safe and effective analgesia sub partu is one of the central issues in optimizing vaginal delivery birth experiences. Meptazinol is a common opiate approved for treating labor pain in the first stage of labor. According to the manufacturer, manual meptazinol can be applied intramuscularly or intravenously. The aim of this study was to compare the two application methods in terms of efficacy in pain relief, occurrence of side effects and treatment satisfaction. Methods 132 patients with singleton term pregnancies and intended vaginal delivery, receiving meptazinol during first stage of labor were included in this prospective cohort study from 05/2020 to 01/2021. We evaluated effectiveness in pain relief and treatment satisfaction using numeric rating scales (NRS) and documented the occurrence of adverse effects. Chi-square test or Fisher exact test were used to compare categorical data and Mann–Whitney U test to compare continuous data between the two treatment groups. Statistical analysis was done by SPSS 27.0. A p value < 0.05 was considered to indicate statistical significance (two tailed). Results Meptazinol decreased labor pain significantly from a NRS of 8 (IQR 8–10) to 6 (IQR 4.75–8) in both treatment groups with no difference in effectiveness between the groups. Frequency of effective pain reduction of a decrease of 2 or more on the NRS did not differ between groups (39.4% vs 54.5%, p = 0.116), as the occurrence of adverse effects. 12% of the newborns were admitted to NICU, the median NApH was 7.195. Conclusion Meptazinol significantly reduces labor pain regardless of the method of application: intramuscular or intravenous. According to our data, no preferable route could be identified. The comparably poorer perinatal outcome in our study cohort hinders us to confirm that meptazinol is safe and can be recommended without restrictions.

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