Syntometrine is a combined injectable pharmaceutical preparation frequently utilized in obstetric practice across Nigeria for the active management of the third stage of labor. It contains two distinct active pharmacological ingredients formulated into a single 1 ml ampoule: oxytocin and ergometrine maleate.
Combining these two agents provides a synergistic clinical effect. The oxytocin component acts almost immediately to initiate sharp uterine contractions, while the ergometrine component takes effect slightly slower but maintains firm uterine tone over a prolonged period, effectively preventing postpartum hemorrhage.
The dual pharmacological action of Syntometrine targets the myometrium through distinct physiological pathways. Oxytocin binds to specific oxytocin receptors on uterine smooth muscle cells, stimulating the release of intracellular calcium ions and triggering prompt, rhythmic contractions. Concurrently, ergometrine acts primarily as a partial agonist at alpha-adrenergic and serotonergic receptors, leading to prolonged vascular and myometrial smooth muscle contraction.
This sustained tonic contraction physically compresses the open maternal blood vessels at the placental site, effectively curtailing blood loss. However, because ergometrine causes widespread vasoconstriction, it also acts on peripheral blood vessels outside the uterus, which can lead to a significant rise in systemic blood pressure.
Syntometrine is indicated primarily for the active management of the third stage of labor (AMTSL) to reduce the incidence of primary postpartum hemorrhage (PPH). Midwives administer it routinely upon the delivery of the anterior shoulder or immediately following the birth of the baby, provided twin gestation has been explicitly ruled out.
It is also utilized in the management of secondary postpartum hemorrhage or postpartum uterine atony when other single-agent oxytocics fail to achieve adequate uterine contraction. It should never be used for the induction or augmentation of labor during the first or second stages, as tetanic uterine contractions can cause fetal distress, uterine rupture, and severe anoxia.
Syntometrine is administered via a single intramuscular (IM) injection of 1 ml. Intravenous administration is generally avoided or used only with extreme caution in rare emergencies because a sudden bolus injection of ergometrine can precipitate acute, severe hypertension and cerebrovascular accidents.
The onset of uterine contraction typically occurs within two to seven minutes following an intramuscular injection. Midwives must ensure the injection is given deep into a large muscle mass, such as the outer thigh or gluteal region, and check that the needle has not entered a blood vessel before pushing the plunger.
Due to the potent vasoconstrictive properties of ergometrine, Syntometrine possesses strict contraindications that every clinician must verify before administration.
| Condition / Status | Clinical Reason for Avoidance |
|---|---|
| Pregnancy (1st/2nd Stage) | Can cause tetanic contractions leading to uterine rupture and fetal asphyxia |
| Hypertension / Preeclampsia | Can worsen high blood pressure or precipitate stroke and seizures |
| Heart Disease | Increases cardiac workload and peripheral resistance dangerously |
| Multiple Gestation | Risk of administering to an undiagnosed second twin still in utero |
| Known Hypersensitivity | Risk of severe allergic or anaphylactic reaction to ergot alkaloids |
Midwives must carefully review the client's antenatal card and medical history to screen for hypertensive disorders before reaching for the Syntometrine ampoule.
Patients receiving Syntometrine frequently experience common side effects due to smooth muscle stimulation throughout the body. Nausea and vomiting are particularly prevalent, often triggered by both the ergometrine and oxytocin components acting on the medullary emetic center. Abdominal cramping, commonly referred to as afterpains, results from powerful uterine contractions.
More serious adverse reactions include transient hypertension, headache, chest discomfort, and peripheral vasoconstriction causing cold extremities. Rare, severe complications comprise acute anaphylaxis, coronary vasospasm, and cerebrovascular hemorrhage resulting from profound blood pressure elevation.
Syntometrine is a temperature-sensitive medication that degrades rapidly when exposed to heat and light. It must be stored in a refrigerator at temperatures between 2°C and 8°C and protected from direct sunlight. Exposure to tropical ambient temperatures without cold-chain maintenance significantly reduces its clinical potency, rendering it ineffective during emergencies.
Midwifery responsibilities include: