These are drugs that inhibit uterine contractions.
Relaxation of the smooth muscle fibres by stimulating the beta receptors present on the cell membrane.
Dosage: 50 mg of ritodrine in 500 ml of 5% glucose solution. Start by 10 drops per minute and increase by 5 drops every 10 minutes until uterine contractions cease.
Other β-sympathomimetic drugs
Action: Antagonise the action of calcium within the myometrial cells so reduce its contractility.
e.g. Nifedipine 10 mg oral tablet.
Action: The intracellular calcium is displaced by magnesium ion leading to inhibition of the uterine activity.
Dosage: The initial dose is 40 cc of 10% solution given slowly IV. The subsequent doses depend upon the response and the development of MgSO4 toxicity so reflexes and respiratory rate should be observed.
Prostaglandin Inhibiting Agents
Action: Inhibition of uterine contractions by inhibiting prostaglandin synthesis.
Dosage: e.g. indomethacin 100 mg suppository initially, followed by 25 mg orally every 6 hours for up to 24 hours after contractions ceased.
It is given IV and the dose is adjusted to maintain blood alcohol level of 0.9-1.6 mg/litre.
Edited by Aldo Campana,