OXYTOCIN INJECTION

(ox-i-toe'sin)

Pitocin
Classifications: hormone; oxytocic;
Therapeutic: oxytocic
Pregnancy Category: X

Availability

10 units/mL injection

Action

Synthetic, water-soluble polypeptide consisting of eight amino acids, identical pharmacologically to the oxytocin released by posterior pituitary. By direct action on myofibrils, produces phasic contractions characteristic of normal delivery. Uterine sensitivity to oxytocin increases during gestation period and peaks sharply before parturition.

Therapeutic Effect

Effective in initiating or improving uterine contractions at term.

Uses

To initiate or improve uterine contraction at term, management of inevitable, incomplete, or missed abortion; stimulation of uterine contractions during third stage of labor; stimulation to overcome uterine inertia; control of postpartum hemorrhage and promotion of postpartum uterine involution. Also used to induce labor in cases of maternal diabetes, preeclampsia, eclampsia, and erythroblastosis fetalis.

Contraindications

Hypersensitivity to oxytocin; significant cephalopelvic disproportion, unfavorable fetal position or presentations that are undeliverable without conversion before delivery, obstetric emergencies in which benefit-to-risk ratio for mother or fetus favors surgical intervention, fetal distress in which delivery is not imminent, prematurity, placenta previa, prolonged use in severe toxemia or uterine inertia, hypertonic uterine patterns, previous surgery of uterus or cervix including cesarean section, conditions predisposing to thromboplastin or amniotic fluid embolism (dead fetus, abruptio placentae), grand multiparity, invasive cervical carcinoma, primipara greater than 35 y of age, past history of uterine sepsis or of traumatic delivery, intranasal route during labor, simultaneous administration of drug by two routes.

Cautious Use

Concomitant use with cyclopropane anesthesia or vasoconstrictive drugs.

Route & Dosage

Labor Induction
Adult: IV 0.5–2 mU/min, may increase by 1–2 mU/min q15–60min (max: 20 mU/min) dose is decreased when labor is established. High dose regimen: 6 mU/min, may increase by 6 mU/min q15–60min until contraction pattern established

Postpartum Bleeding
Adult: IM 10 U total dose IV Infuse a total of 10–40 U at a rate of 20–40 mU/min after delivery

Incomplete Abortion
Adult: IV 10–20 mU/min

Administration

Intravenous

PREPARE: IV Infusion: When diluting oxytocin for IV infusion, rotate bottle gently to distribute medicine throughout solution. IV Infusion for Inducing Labor: Add 10 U (1 mL) to 1 L of D5W, NS, RL, or D5NS to yield 10 mU/mL. IV Infusion for Postpartum Bleeding/Incomplete Abortion: Add 10–40 U (1–4 mL) to 1 L of D5W, NS, RL, or D5NS to yield 10–40 mU/mL.

ADMINISTER: IV Infusion: Use an infusion pump for accurate control of infusion rate. IV Infusion for Inducing Labor: Initially infuse 0.5–2 mU/min; increase by 1–2 mU/min at 30–60 min intervals. IV Infusion for Postpartum Bleeding: Initially infuse 10–40 mU/min, then adjust to control uterine atony. IV Infusion for Incomplete Abortion: Infuse 10–20 mU/min. Do not exceed 30 U in 12 h.

INCOMPATIBILITIES Solution/additive: Fibrinolysin, norepinephrine, prochlorperazine, warfarin.

Adverse Effects (≥1%)

Body as a Whole: Fetal trauma from too rapid propulsion through pelvis, fetal death, anaphylactic reactions, postpartum hemorrhage, precordial pain, edema, cyanosis or redness of skin. CV: Fetal bradycardia and arrhythmias, maternal cardiac arrhythmias, hypertensive episodes, subarachnoid hemorrhage, increased blood flow, fatal afibrinogenemia, ECG changes, PVCs, cardiovascular spasm and collapse. GI: Neonatal jaundice, maternal nausea, vomiting. Endocrine: ADH effects leading to severe water intoxication and hyponatremia, hypotension. CNS: Fetal intracranial hemorrhage, anxiety. Respiratory: Fetal hypoxia, maternal dyspnea. Urogenital: Uterine hypertonicity, tetanic contractions, uterine rupture, pelvic hematoma.

Interactions

Drug: vasoconstrictors cause severe hypertension; cyclopropane anesthesia causes hypotension, maternal bradycardia, arrhythmias. Herbal: Ephedra, ma huang may cause hypertension.

Pharmacokinetics

Duration: 1 h. Distribution: Distributed throughout extracellular fluid; small amount may cross placenta. Metabolism: Rapidly destroyed in liver and kidneys. Elimination: Small amounts excreted unchanged in urine. Half-Life: 3–5 min.

Nursing Implications

Assessment & Drug Effects

Start flow charts to record maternal BP and other vital signs, I&O ratio, weight, strength, duration, and frequency of contractions, as well as fetal heart tone and rate, before instituting treatment.
Monitor fetal heart rate and maternal BP and pulse at least q15min during infusion period; evaluate tonus of myometrium during and between contractions and record on flow chart. Report change in rate and rhythm immediately.
Stop infusion to prevent fetal anoxia, turn patient on her side, and notify physician if contractions are prolonged (occurring at less than 2-min intervals) and if monitor records contractions about 50 mm Hg or if contractions last 90 sec or longer. Stimulation will wane rapidly within 2–3 min. Oxygen administration may be necessary.
If local or regional (caudal, spinal) anesthesia is being given to the patient receiving oxytocin, be alert to the possibility of hypertensive crisis (sudden intense occipital headache, palpitation, marked hypertension, stiff neck, nausea, vomiting, sweating, fever, photophobia, dilated pupils, bradycardia or tachycardia, constricting chest pain).
Monitor I&O during labor. If patient is receiving drug by prolonged IV infusion, watch for symptoms of water intoxication (drowsiness, listlessness, headache, confusion, anuria, weight gain). Report changes in alertness and orientation and changes in I&O ratio (i.e., marked decrease in output with excessive intake).
Check fundus frequently during the first few postpartum hours and several times daily thereafter.
Incidence of hypersensitivity or allergic reactions is higher when oxytocin is given by IM or IV injection rather than by IV infusion (diluted solution).

Patient & Family Education

Be aware of purpose and anticipated effect of oxytocin.
Report sudden, severe headache immediately to health care providers.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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