Oxytocin stimulates uterine contractions at birth, smooth muscle contraction in the mammary glands during sucking, maternal behavior and affects water homeostasis. It is not known whether or not oxytocin secretion affects water homeostasis in normal individuals, but pharmacological doses of oxytocin, such as those used for abortion and sometimes for induction of labor, alter the exchange of hydrogen by the kidneys. One unit of oxytocin (uterotonic activity) has about 0.01 IU of antidiuretic activity. Severe water poisoning can occur in women who receive infusions of oxytocin (>20 mIU / min) and at the same time receive hypotonic fluids of more than 3.5 l. Antidiuresis is remarkable at infusion rates of 15 mIU/min and diuresis is almost maximum at 30 mIU/min. The antidiuretic effect occurs 10 to 15 minutes after the start of the infusion and lasts 10 to 15 minutes after the end of the infusion in Reeves et al. (1998). Dinoproston stimulates the smooth muscles of the uterus and GI. Although it is believed that the drug exerts its uterine action by direct myometric stimulation, the exact mode of these and other actions has not been fully elucidated. Dinoprostone increases the amplitude and frequency of uterine contractions during pregnancy, but the uterus`s response to the drug increases with the duration of pregnancy. In early pregnancy, the uterus reacts more strongly to dinoprostone than to oxytocin. Dinoproston-induced uterine contractions are usually sufficient to cause evacuation of the fetus and placenta. The drug also produces cervical dilation and softening.
Dinoprostone causes stimulation of the circular smooth muscles of the gastrointestinal tract, causes bronchodilation and increases the permeability of the vessels. High doses of dinoprostone can cause vasodilation and hypotension. Try PMC Labs and let us know what you think. Find out more. In the term, maternal uterine contractions cause the fetus to be forced out of the womb, a process called childbirth. Uterine contractions usually begin at the top of the uterine fundus and spread to the cervix. Uterine contractions in the last trimester increase the strength of the uterine muscle. Called Braxton-Hicks contractions, these are slow, rhythmic contractions of the uterine myometrium. Accidental ingestion of ergot alkaloids in contaminated cereals, as well as overdose of ergot remedies, cause ergot poisoning. The most dramatic effects of poisoning are hallucinations and convulsions, prolonged vasospasm and damage to the endothelium, which can lead to gangrene, and stimulation of the smooth muscles of the uterus, which can lead to abortion during pregnancy. In this review, we give an overview of the mechanisms responsible for contractility and relaxation of the uterus. We then use it as a basis to discuss the two main uterotonins, oxytocin and prostaglandins, followed by currently available (although often unauthorized) tocolytics; Progesterone, magnesium, calcium channel blockers, oxytocin receptor blockers, β-adrenergic receptor agonists, prostaglandin synthesis inhibitors and nitric oxide donors.
In this brief overview, we focused on the main mechanisms of action and data obtained on human tissues. By focusing on mechanisms, meta-analyses and Cochrane literature reviews, our aim is to provide information on clinical benefits and show where further research is needed and where the objectives may be. To confirm this hypothesis, they gave atropine and pineapple together. Since atropine is the antagonist of mucarinic receptors and the two give pineapple together, the contraction of the uterus should not be generated if the effect is due to muscarinic receptors, but in fact, it has always produced the same effect and contracted the uterus, which means that the effect is not due to muscaric receptors, but to histamine H2 receptors, which are also abundant in the uterine muscles. However, they did not perform a test to determine whether the effect was due to histamine receptors (Aucelio, 1988; Choppin et al., 1999; Kitazania et al., 2007). Drugs, strengthening rhythmic contractions of the uterus This group includes oxytocin, deaminooxytocin, pituitary gland, hyphotocine, dinoprost, dinoprostone, pachycarpine and proserine. They are indicated during the weakness of work activity, for the normalization of uterine involution in the postpartum period, during hypotonic uterine bleeding. Oxytocin is a hormone secreted by neurons in the hypothalamus and stored in the posterior pituitary gland in mammals. Commercially available oxytocin preparations are produced synthetically. Oxytocin stimulates the contraction of the smooth muscles of the uterus by increasing the sodium permeability of uterine mufifibrils.
High concentrations of estrogen lower the uterus`s response threshold to oxytocin. The uterine response to oxytocin increases with the duration of pregnancy. In the term uterus, oxytocin increases the amplitude and frequency of uterine contractions, which in turn tend to decrease cervical activity, which leads to dilation and extinction of the cervix and temporarily hinders blood circulation in the uterus. Oxytocin triggers milk sputum in breastfeeding women. It also produces vasodilation of smooth vascular muscles and increases renal, coronary and cerebral blood flow. When the effects of progesterone and its analogue were tested in vitro on myometric strips, only progesterone and not 17OHPC was effective in reducing myometric contractility, which is difficult to explain according to our current understanding. Antigestins, including mifepristone (RU 486), are designed to combat the action of progesterone and have clinical use for induction of labour or medical abortion in early or mid-trimester. Studies in mice have shown that mifepristone can induce labor in late pregnancy, while oral administration of mifepristone to women increases uterine activity. These drugs are mainly used to stop preterm labor and weaken work activity during attached labor to prevent trauma.
For these purposes, β2-adrenomimetics (fenoterol), magnesium sulfate, narcotics are used. The partusist (Fenoterol) is a β2-adrenomimetic. It causes a toxic effect (uterine relaxation). In addition, it leads to bronchodilation. The agent is an effective drug for the prevention of preterm labor and does not cause a negative effect on the fetus. It is administered intravenously in drops and orally in tablets. It can cause tachycardia, muscle weakness, tremors and hypotension. It is contraindicated in heart defects, arrhythmia, thyrotoxicosis and glaucoma.
In medical practice are used: galena (thick ergot extract), neo-galena drugs (ergotal) and pure alkaloids (ergometrine maleate, methylergometin, ergotamine hydrotartrate). Ergotamine is used to treat migraines. The beneficial effect of ergotamine is related to the weakening of the pulsation of the cerebral vessel and the reduction of irritation of the receptors of the brain envelope. Ergot alkaloids are contraindicated in angina pectoris, atherosclerosis and spasms of peripheral vessels. They are excreted in breast milk, so they are not allowed to be used during feeding. Ergometrine and methylergometrine are oxytomics. Small doses cause rhythmic contractions of the uterus, but with larger doses, they become more or less continuous. They have little effect on other smooth muscles. Syntocinon (synthetic oxytocin) is used because natural oxytocin contains small amounts of vasopressin. It is administered by intravenous infusion, a total dose not exceeding 5 units for induction of labor for medical reasons (hypotonic uterine inertia) and in case of incomplete, inevitable or missed abortion. Syntometrine (a mixture of ergometrine 500 micrograms and oxytocin 5 units) is used to prevent postpartum bleeding after childbirth in high-risk cases.
These funds can improve the natural process of uterine contraction, which successfully stops postpartum blood loss and eventually leads to normal uterine involution to the preimpregnation state. Ergot alkaloids have a stimulating effect on the uterus. The uterus is more sensitive to ergot at birth than at the beginning of pregnancy and much more sensitive than the non-pregnant organ. These drugs induce a strong and prolonged tonic contraction of the uterus. Ergometrine is more selective than other ergot alkaloids in influencing the uterus and is the drug of choice for obstetric applications of these drugs. Ergometrine can be administered enterally and parenterally. .