Terbutaline

UNDER REVIEW (September 2016)

Mechanism of Action:

Selective short-acting beta-2 adrenoceptor agonist i.e. has minimal effect on beta-1 adrenoceptors and is inactive at alpha-adrenoceptors. Actions of beta-2 adrenoceptor (a seven-transmembrane G-protein-coupled receptor) include: bronchodilation, vasodilation, smooth muscle relaxation. Its actions are achieved through activation of adenylate cyclase, which causes the formation of cylic AMP (second messenger) from ATP.

Lecture and CAL materials:

Ritodrine

UNDER REVIEW (September 2016)

Mechanism of Action:

Selective short-acting beta-2 adrenoceptor agonist i.e. has minimal effect on beta-1 adrenoceptors and is inactive at alpha-adrenoceptors. Actions of beta-2 adrenoceptor (a seven-transmembrane G-protein-coupled receptor) include: bronchodilation, vasodilation, smooth muscle relaxation. Its actions are achieved through activation of adenylate cyclase, which causes the formation of cylic AMP (second messenger) from ATP.

Lecture and CAL materials:

Mifepristone

UNDER REVIEW (September 2016)

Mechanism of Action:

Progesterone antagonist. Blocks the action of progesterone on the superficial endometrium of the uterus, hence causes its decay and shedding. As a result, the blastocyst (fertilized egg) does not get the necessary nutrition, and is unable to attach to the uterus. Partial progesterone receptor agonist – increases sensitivity of uterus to prostaglandins and dilates the cervix.

Lecture and CAL materials:

  • RU 486 ®

Gemeprost

UNDER REVIEW (September 2016)

Mechanism of Action:

Prostaglandin E1 analogue. Causes cervical dilatation by activating collagenase in cervix (cervical ripening). Also causes uterine contractions. Gemeprost acts on PGE2 receptors in myometrium. Contraction causes expulsion of uterine contents.

Lecture and CAL materials:

  • Lecture:

Medroxyprogesterone

UNDER REVIEW (September 2016)

Mechanism of Action:

A long-acting progestogen (derivative of progesterone) – mimics action of progesterone by combining with progesterone nuclear receptor and affecting gene transcription and protein synthesis.

Lecture and CAL materials:

Ethinyloestradiol

UNDER REVIEW (September 2016)

Mechanism of Action:

Mimics action of oestradiol by combining with oestrogen nuclear receptor and affecting protein synthesis.

Lecture and CAL materials:

Misoprostol

Indications:

  • Gastric protection during therapy with NSAIDs
  • Therapeutic abortion (with the anti-progestogen agent mifepristone and usually methotrexate)
  • Can be used in induction of labour

Mechanism of Action:

Prostaglandin E (EP) receptor agonist. EP receptors are seven-transmembrane G-protein-coupled receptors.

Lecture and CAL materials: (under review)

Ergometrine

UNDER REVIEW (September 2016)

Mechanism of Action:

Ergometrine maleate is an ergot alkaloid which probably acts on 5HT and alpha-adrenergic receptors found in the walls of blood vessels and in the uterus. Ergometrine causes constriction of the blood vessels and contraction of the uterus. Intense contraction of the muscles of the uterus causes the blood supply of the placenta (placental bed) to shrink back into the uterus. It also causes shortening and kinking of the blood vessels in the uterus. Contraction of the muscle in the blood vessel walls causes the blood vessels to narrow and reduces blood flow. Both these actions reduce blood loss following delivery. In normal labour, these contractions occur naturally after delivery, to prevent bleeding from the placental blood source. Ergotmetrine is given if this response is deficient allowing post-partum haemorrhage.

Lecture and CAL materials:

  • Lecture:

Oxytocin

UNDER REVIEW (September 2016)

Mechanism of Action:

Oxytocin, a peptide hormone released from the posterior pituitary gland, is important in contraction of muscles. Among the effects of oxytocin are: stimulation of lactation (contraction of muscle cells surrounding the alveoli of the mammary gland), and uterine contractions. At the end of pregnancy, oestrogen causes the number of oxytocin receptors to increase, causing the uterus to be more responsive to oxytocin. Synthetic oxytocin is used clinically.

Lecture and CAL materials:

  • Lecture:

Dinoprostone

UNDER REVIEW (September 2016)

Mechanism of Action:

A PGE2 analogue. Activates collagenase in the cervix to hasten ‘ripening’ and dilates the cervix prior to vaginal delivery. It is also associated with contractions of the uterus that are probably a direct effect.

Lecture and CAL materials:

  • Lecture: