Oxytocin

Oxytocin is a hormone that plays a crucial role in reproductive physiology, social behavior and emotional bonding. It is produced in the hypothalamus and secreted by the pituitary gland in response to various stimuli, including sexual activity or child birth or breastfeeding.

Indications and use

Oxytocin is used primarily in obstetrics and gynecology to induce or augment labor, control postpartum bleeding, and facilitate breastfeeding. It is also used to accelerate placental abruption after delivery. The hormone is also used in certain diagnostic procedures, such as the labor stress test, which assesses placental function.

Oxytocin has been studied as a possible treatment for several psychiatric disorders, including autism spectrum disorders, anxiety, and depression. However, no studies have demonstrated efficacy for these indications.

History

Oxytocin was discovered by Sir Henry H. Dale in 1909. It was found to contract the uterus during childbirth and facilitate the release of breast milk. Vincent du Vigneaud identified the structure of oxytocin in 1953, which led to the first synthesis of a peptide hormone and earned him the Nobel Prize in Chemistry.

Physiology and pharmacodynamics

Oxytocin plays an important role in labor and delivery. The hormone is produced in the hypothalamus and released from the paraventricular nucleus to the posterior pituitary gland, where it is stored. It is then released in bursts during labor to stimulate uterine contractions.

Oxytocin binds to oxytocin receptors (OXTR) in the uterine myometrium, triggering the G protein-coupled receptor signaling cascade that leads to increased intracellular calcium concentrations. Elevated calcium levels activate myosin light chain kinase, which in turn induces the formation of the contractile protein actomyosin. This stimulates uterine smooth muscle contractions. The substance also stimulates smooth muscle in the mammary glands, resulting in lactation. The density of oxytocin receptors on the myometrium (the muscular layer of the uterine wall) increases significantly during pregnancy and peaks in early labor, making the effect of oxytocin particularly strong at this time.

Oxytocin is one of the few hormones in the body that is regulated by positive feedback rather than negative feedback. For example, when pressure is applied to the cervix by the fetal head, this signals the release of more oxytocin from the posterior pituitary gland. The increased oxytocin then travels to the uterus where it stimulates and further enhances uterine contractions. The induced uterine contractions, in turn, stimulate the release of increasing amounts of oxytocin. This positive feedback loop continues until the baby is born.

Because exogenously administered oxytocin and endogenously released oxytocin have the same effects on the female reproductive system, synthetic oxytocin may be used in certain cases during the antepartum and postpartum periods to induce or enhance uterine contractions.

Pharmacokinetics

Oxytocin is administered as an intravenous infusion or intramuscular injection. The onset of action is rapid, usually within a few minutes. The duration of the effect depends on the dose and individual response. Oxytocin is broken down in the liver and excreted in the urine. The enzyme oxytocinase is largely responsible for the metabolism and regulation of oxytocin levels during pregnancy.

Drug interactions

There are no known interactions with other drugs.

Contraindications

In some situations, the use of oxytocin is contraindicated. These include:

• Allergies to the active ingredient
• Pregnancy hypertension (preeclampsia)
• Tendency to continuous contraction of the uterus (tetanus uteri)
• In case of hypertonic contractions
• In case of imminent uterine rupture
• In the presence of too much amniotic fluid
• Incorrect position of the placenta
• Premature placental abruption
• In case of a pre-displaced placenta
• In case of immature cervix
• Imminent acute oxygen deficiency of the child
• In case of placental deficiency
• In case of positional anomalies
• In the case of a mechanical birth obstruction such as head/pelvis mismatch
• In case of umbilical cord entanglement

Side effects

Oxytocin can potentially cause serious side effects in the mother. For example:

• Drastic changes in heart rate (tachycardia, bradycardia).
• Excessive bleeding long after delivery
• severe headaches
• blurred vision
• Throbbing in the neck or ears
• confusion
• severe weakness
• Susceptibility to fluctuations

Oxytocin can cause serious or life-threatening side effects in the newborn, including:

• Slow heartbeat or other abnormal heart rates;
• Jaundice
• Seizures
• Eye problems
• Problems with breathing, muscle tone, and other signs of health problems

Common side effects of oxytocin may include:

• Nausea
• Vomiting
• Stronger or more frequent contractions (this is a desired effect of oxytocin).

Pregnancy

Based on extensive clinical experience and the chemical structure and pharmacological properties of this drug, no risk of fetal malformations is expected when used as directed.