This randomized, double-blind, placebo-controlled trial aims to compare the analgesic efficacy and obstetric effects of tramadol (100 mg IV) versus paracetamol (1 g IV) versus placebo (saline solution) in nulliparous women during active labor. The primary outcome is duration of active labor (minutes). Secondary outcomes include duration of expulsive phase, type of delivery, need for oxytocin augmentation, maternal adverse events (nausea, vomiting, somnolence, hypotension), and neonatal outcomes (Apgar scores at 1 and 5 minutes, NICU admission). The study hypothesizes that tramadol significantly reduces active labor duration compared to paracetamol and placebo, without compromising maternal or neonatal safety. A total of 300 nulliparous women (100 per group) will be enrolled at Hospital Escuela, Tegucigalpa, Honduras.
Nulliparous pregnant women
Age between 15 and 45 years
Singleton pregnancy, term (37-41 weeks gestation)
Cephalic presentation
Multiple gestation or high-risk pregnancy (preeclampsia, gestational diabetes, etc.)
Known allergy or contraindication to tramadol or paracetamol
Recent use (less than 6 hours) of any analgesic medication
Previous cesarean section or other uterine surgery
Parallel
Tramadol Hydrochloride
DrugTramadol 100 mg administered as a single intravenous dose at the onset of active labor. Tramadol is an atypical opioid analgesic with serotonin and noradrenaline reuptake inhibition properties. The dose is within standard clinical ranges for obstetric analgesia. Administration is performed by trained medical personnel following institutional protocols. Participants are monitored for adverse effects including nausea, vomiting, somnolence, dizziness, and hypotension.
Paracetamol (acetaminophen)
DrugParacetamol 1 g administered as a single intravenous slow infusion at the onset of active labor. Paracetamol is a central analgesic acting through COX-3 inhibition in the central nervous system. It is widely used during pregnancy and labor due to its favorable safety profile. Administration is performed by trained medical personnel following institutional protocols. Participants are monitored for adverse effects including nausea, vomiting, and allergic reactions (rare).
Placebo (Saline Solution)
DrugPlacebo consisting of 10 mL 0.9% saline solution administered as a single intravenous dose at the onset of active labor. The appearance and administration procedure are identical to the active interventions to maintain blinding. No pharmacological active ingredients are present. Administration is performed by trained medical personnel following institutional protocols.
Duration of Active Labor
Time in minutes from administration of study intervention (at onset of active labor defined as cervical dilation ≥4 cm with regular contractions) to complete cervical dilation (10 cm) or delivery, whichever occurs first. Measured and recorded by attending obstetric staff using standardized timing protocols.
Duration of Expulsive Phase (Second Stage)
Time in minutes from complete cervical dilation (10 cm) to fetal expulsion. Measured and recorded by attending obstetric staff.
Type of Delivery
Classification of delivery outcome: spontaneous vaginal delivery, instrumental delivery (forceps or vacuum), or cesarean section. Assessed by attending obstetrician.
Need for Oxytocin Augmentation
Requirement for additional oxytocin administration to augment uterine contractions during labor. Recorded as yes/no, including dose and timing if applicable.
Maternal Adverse Events
Occurrence of any adverse events potentially related to the intervention, including: nausea, vomiting, somnolence, dizziness, headache, pruritus, hypotension (systolic BP \<90 mmHg), or allergic reactions. Severity graded as mild, moderate, or severe.
Subgroup Analysis by Maternal Age
Comparison of primary and secondary outcomes stratified by maternal age categories (\<20 years, 20-35 years, \>35 years).
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