drugs for treatment of threatened preterm labor | preterm labor is a common pregnancy-time-limited disease in obstetrics, with an incidence rate of 5% ~ 15%. the main principle of preterm labor treatment is to inhibit uterine contraction through the application of uterine contraction inhibitors, prolong the time of fetus in utero, and win the time of fetal lung maturation for the fetus to improve the outcome of newborns. At present, domestic and foreign drugs for the treatment of premature delivery include ritodrine hydrochloride (Anbao), magnesium sulfate, nifedipine, atosiban and other drugs. Ritodrine hydrochloride (Ritodrine Hydrochlo ride), the chemical name is p-hydroxy-α- [1-[ (p-hydroxyphenylethyl) amino] ethyl] benzyl alcohol hydrochloride, also known as hydroxybenzyl hydroxyephedrine hydrochloride, It is a β-sympathomimetic drug, which is an adrenergic β2 receptor agonist, which can inhibit uterine contraction. It is currently the only drug certified by the US Food and DrugAdmini stration , FDA for the treatment of threatened preterm labor, has been included in the "United States Pharmacopoeia. By binding to the β2 receptor on the surface of uterine muscle cells, it activates the adenylate cyclase of the cell membrane, converts adenosine triphosphate into cyclic adenosine phosphate, reduces the activity of myosin light chain kinase, and inhibits the release of calcium from the sarcoplasmic reticulum. Reduce the concentration of calcium ions in the cell, thereby inhibiting the contraction of uterine muscle fibers. Since ritodrine hydrochloride has an agonistic effect on the β1 receptor, the heart rate can be accelerated at the initial stage of medication. Generally, there is a dose-effect relationship. When the heart rate of pregnant women reaches 120 beats/min, the effect of inhibiting contractions is obvious, but as the use time is prolonged, The heart rate gradually stabilizes and has a downward trend. This is a desensitization phenomenon of ritodrine hydrochloride. In addition, the use of ritodrine hydrochloride in a small number of pregnant women can cause abnormal liver function, blood sugar and potassium, pulmonary edema, etc. Clinically, it mainly acts on the myometrium. By binding to the β2 receptor on the cell membrane of the uterine smooth muscle, it activates adenylate cyclase, increases the concentration of intracellular cAMP, reduces the concentration of intracellular free calcium, and relaxes the uterine smooth muscle. Reduce the activity of the uterus to prolong the pregnancy and prevent premature delivery after 20 weeks of pregnancy. Fig. 1 is ritodrine hydrochloride injection |