Drug that given to increase pain during labor
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Finding Sources
Finding Sources
Reading File
Drug Given to Increase Pain During Labor
This is a classic pharmacology/obstetrics exam trick question. The answer is:
Oxytocin (Pitocin / Syntocinon)
Oxytocin is the drug given during labor that increases pain - not by any analgesic action, but by augmenting and intensifying uterine contractions, which directly increases the pain experienced by the mother.
Why Oxytocin Increases Pain
Oxytocin acts on oxytocin receptors in the uterine myometrium, causing stronger and more frequent contractions. By intensifying contractions:
- Uterine pressure rises
- Ischemia of the myometrium increases
- The duration and frequency of painful contractions increases
This is the opposite of pain relief - it is used to speed up labor, not comfort the patient.
Clinical Uses (from Goodman & Gilman's)
| Use | Dose |
|---|---|
| Labor induction | IV infusion starting at 6 mIU/min, up to 40 mIU/min |
| Augmentation of dysfunctional labor (hypotonic contractions) | ~10 mIU/min IV infusion |
| Postpartum hemorrhage (uterotonic) | Standard IV/IM doses |
"Oxytocin also is used when spontaneous labor is not progressing at an acceptable rate. To augment hypotonic contractions in dysfunctional labor, an infusion rate of 10 mIU/min typically is sufficient."
- Goodman & Gilman's Pharmacological Basis of Therapeutics
Key Points for Exams
- Oxytocin increases pain by augmenting uterine contractions
- It does NOT have any analgesic properties
- Complications of overuse include: uterine hyperstimulation, uterine rupture, fetal distress (compromised oxygenation), and water intoxication (antidiuretic effect at high doses due to structural similarity to vasopressin)
- Contraindicated if more than 5 contractions per 10-minute interval occur (uterine hyperstimulation)
- Its short half-life (12-15 min IV) means effects dissipate quickly if infusion is stopped
In contrast, drugs used to relieve labor pain include epidural anesthetics (bupivacaine, ropivacaine), opioids (fentanyl, meperidine), and nitrous oxide - none of which augment contractions.
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