Relevant pharmacology

Little of the pharmacological treatment of the female reproductive system involves modulation of the innervation or activation and inhibition of receptors to neurotransmitters. Drugs having direct effects on uterine smooth muscle are important for the induction of abortions, for the induction and augmentation of labour and for the suppression of premature labour. Vasoconstrictor drugs are of use for the suppression of postpartum haemorrhage.

Oxytocin is used to enhance uterine contractions during labour. The sensitivity of the uterine smooth muscle to oxytocin increases during pregnancy, and is at its maximum at parturition, when oxytocin from the posterior pituitary causes regular co-ordinated contractions that sweep along the uterus without significantly increasing the intrauterine pressure (which would be dangerous, as it can reduce or block placental blood flow). Intravenous oxytocin can enhance the amplitude and frequency of the contractions, and only at very high doses is there danger of sustained contractions. Ergometrine is also a powerful stimulant of uterine contraction, and before the isolation of oxytocin was used for induction of labour. However, it produces prolonged contractions of the smooth muscle and an elevation glycogen content. Lubrication of the vagina is from the secretions of the cervix, but the high glycogen content allows bacteria within the vagina to form lactic acid, which keeps the vaginal fluid acid. The vagina is a very vascular organ, and is supplied by sympathetic and parasympathetic nerves, which may be important in controlling the blood flow - the parasympathetic fibres are vasodilatory. Sensory nerves leave the vagina by way of the pudendal plexus.

of uterine tone. It is thus dangerous to use during parturition, but valuable chapter 10 to prevent postpartum bleeding. Induction of labour and abortion can also Renal, Urinary be achieved by the use of prostaglandins E and F, which are often given and Reproductive as vaginal pessaries. Prostaglandins are produced in the myometrium and Tract Systems endometrium and also have effects on the non-pregnant uterus. Dysmenor-rhoea is associated with increased natural production, and can be treated with non-steroidal anti-inflammatory drugs. Activation of (^-adrenoceptor agonists will relax uterine smooth muscle, and such drugs as salbutamol and ritodrine have been used as tocolytic agents to try to suppress premature labour.

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