Pharmacology of oxytocin

Introduction to oxytocin

Oxytocin, also known as 3-isoleucine-8-leucine, synthetic oxytocin, is a uterine contraction drug and anti-fertility drugs. In medicine is mainly used in induction of labor, oxytocin, postpartum hemorrhage and uterine insufficiency; nasal drip for breast-feeding; oxytocin irritation test.

Pharmacology of oxytocin

Oxytocin by indirect stimulation of uterine smooth muscle contraction, mimicking the normal uterine contraction of childbirth, leading to cervical dilatation, uterine response to oxytocin in the process of pregnancy gradually increased, full term peak. ② to stimulate the smooth muscle contraction of the breast, helps milk from the breast discharge, but does not increase the breast milk secretion.

Oxytocin can easily be digested by digestive juice, nasal nasal mucosa is quickly absorbed, the role of aging for about 20 minutes; intramuscular injection in 3 to 5 minutes onset, the role of sustained 30 to 60 minutes; intravenous infusion immediately Effect, 15 to 60 minutes of uterine contraction frequency and intensity gradually increased, and then stable, 20 minutes after the infusion, the effect gradually diminished. Half-life is generally 1 to 6 minutes. The goods by the liver, kidney metabolism, excretion by the kidney, a very small amount of the original.

The clinical application of oxytocin

Oxytocin in medicine mainly used in induction of labor, oxytocin, postpartum and abortion due to uterine contraction or poor recovery caused by uterine bleeding; understanding placental reserve function (oxytocin irritation test); nasal discharge can promote breast milk.

oxytocin usage dosage

1. Induction of labor or oxytocin intravenous infusion, a 2.5-5 units, with sodium chloride injection diluted to 0.01 ml per 1ml. Intravenous infusion at the beginning of each minute does not exceed 0.001-0.002 units, every 15-30 minutes increase 0.001-0.002 units, to achieve contractions and normal childbirth similar to the fastest minute of not more than 0.02 units, usually 0.002-0.005 per minute unit.
2. Control postpartum hemorrhage per minute intravenous 0.02-0.04 units, placenta can be injected after intramuscular injection of 5-10 units.
3. Prolactin 2-3 minutes before feeding, with a drop of nasal drops 3 drops, dropping one or both sides of the nostrils.

(1) 0.5ml: 2.5 units

(2) 1ml: 5 units

(3) 1ml; 10 units

oxytocin nasal drops 1ml: 40 units

(1). Induction or prenatal uterine contraction weakness: 2.5-5 units by adding 5% glucose solution 500ml for slow intravenous infusion (10-30 drops / min), the amount of a 20 units.

(2). 5-10 units per intramuscular injection, or intravenous infusion in 5% glucose solution.

Oxytocin can cause adverse reactions

Occasional nausea, vomiting, increased heart rate or arrhythmia.

May cause allergic reactions: rash, drug fever, facial flushing or pale, asthma, palpitations, chest tightness, abdominal pain. Allergic shock, water retention .Newborns may be hyponatremia, convulsions.

Use oxytocin contraindications

(1) the following circumstances should be disabled: the birth of the head of the basin is not called, umbilical cord exposed or prolapse, complete placenta previa, pre-vascular, fetal distress, contraction is too strong, need immediate surgery obstetric emergency or uterus Shortage of long-term medication.

(2) the following circumstances should be used with caution; with hypertonic saline stop pregnancy abortion, placental abruption, severe pregnancy-induced hypertension syndrome, heart disease, critical cephalopelvic disproportion, multiple births, uterus too large, had Intrauterine infection history, injury history of dystocia, uterine or cervix have surgical treatment (including secondary palace history), cervical cancer, partial placenta previa, premature delivery, fetal head is not convergence, fetal position or fetal first exposed parts Normal, pregnant women have more than 35 years of age should be careful.

Heart disease, there are broken abdominal history of the use of more than three tires by the disabled. Transverse, pelvic too narrow, birth barriers, obviously do not call the head is hanged.

Drugs that interact with oxytocin

(1) cyclopropane and other hydrocarbons inhalation of general anesthesia, the use of oxytocin can lead to maternal hypovolemia, sinus bradycardia or (and) atrioventricular rhythm disorders. Enhalonol concentration> 1.5%, halothane concentration> 1.0% inhalation of general anesthesia, the effect of uterine on oxytocin weakened. Enflurane concentration> 3.0% can eliminate the reaction, and can lead to uterine bleeding.

(2) other uterine contractions and oxytocin at the same time, can make uterine tension is too high, resulting in uterine rupture or cervical tear.

With oxytocin before the inspection and monitoring:

① the frequency of uterine contraction, duration and intensity;

② pregnant women pulse and blood pressure;

③ fetal heart rate;

④ uterine muscle tension during resting;

⑤ Fetal maturity;

⑥ pelvic size and fetal decline in the situation;

⑦ the amount of liquid out of the balance (especially for a long time users).