Beta-mimetic Drugs in Obstetrics and Perinatology [antikvár]

General Remarks on Treatment with Beta-mimetics H. Jung At present jS-mimetics are most effective agents to inhibit premature labor contractions. They are active by intravenous and oral use and reach full effectiveness within a few minutes in relation to the blood concentration. There is a linear correlation between the contraction inhibiting effect and the concentration of the j3-mimetic substance in the blood. |3-mimetics are acting via the |3-2-receptors of the muscle fibre of the uterus. The uterus muscle cell regulates its function by transmitter substances, which are acting on the a-and/3-receptors (Fig. 1). A stimulation of the a-receptors by substances as Nor-Adrena-lin initiates contractions, a-blocking substances are able to inhibit this action. But they are not usable for therapy in men. In contrast, ^-stimulating substances can inhibit the muscle fibre via the ^-receptors. The a- and /J-receptors are generally theoretical models today. The transmitting substances related to the receptors are known. While Nor-Adrenalin is acting on the a-receptor and contracts the uterus muscle, Adrenalin primarily has an affinity to the /3-receptor during pregnancy and is able to inhibit uterine contraction. As we have observed in our own experiments, Estrogens stimulate the sensitivity of the a-receptors. In contrast, Progesterone stimulates the |3-2-receptor-effects and assists the inhibiting effect of the j3-mimetics (Jung and Klock). Via the enzyme Adenylcyclase ^-adrenergic stimulation initiates an increase of cAMP by inhibiting the energy producing process from ATP (Fig. 2). Calcium plays an important role in the process of muscle relaxation. In addition j3-mimetics also effect the activity of the muscle cell immediately at the cell membrane via electrobiological phenomena. For the actual investigation and the clinical value of uterine contractions and beginning of labor it is important to know, that Prostaglandins influence the stimulating process