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Reproductive Pharmacology > Drugs affecting Uterine Motility > Flashcards

Drugs affecting Uterine Motility Flashcards

1
Q

What are the main objectives of drugs affecting uterine motility?

A
  1. To induce & augment labour
  2. To control post partum haemorrhage (PPH)
  3. To induce pathological abortion
  4. To arrest premature labour
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2
Q

What are the 3 clinical uses of uterine stimulants?

A
  1. To induce abortion in the first half of pregnancy
  2. To induce or augment labour in late gestation
  3. To prevent or arrest PPH- Common cause of maternal death
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3
Q

How do uterine motility drugs help with postpartum haemorrhage?

A

through stimulation of tonic contractions that constrict uterine blood vessels
- necessary to prevent excessive blood loss

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4
Q

Name the drugs that stimulate uterine contractility?

A
  1. Oxytocin - Syntocinon ®
  2. Ergot alkaloids - Ergometrine
  3. Prostaglandins - Misoprostol, Gameprost, PGE, PGF2 α
  4. Miscellaneous - Quinine, Emetine, Alcohol
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5
Q

Name the drugs that relax uterine muscles?

A
  1. β2 Selective stimulants - Ritodrine, Salbutamol
  2. Oxytocic antagonist - Atosiban
  3. COX inhibitors - Celecoxib, Aspirin,
    Indomethacin, Ibuprofen
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6
Q

Describe oxytocin and its effect?

A
  • Has short half life

- contractions lasting a few minutes therefore has to be infused

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7
Q

In what case is oxytocin the least effective?

A

in early pregnancy

- due to low density of oxytocin receptors

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8
Q

When can oxytocin be used?

A
  1. Induction of labour for medical reasons
  2. Augmentation of labour in hypotonic uterine inertia
  3. Can also be used following incomplete abortion after 20 weeks (prostaglandins a preferred choice)
  4. In high doses used to induce abortion
  5. May be used after full-term delivery to prevent and treat PPH
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9
Q

Describe the mode of administering

oxytocin in different cases?

A
  1. Given by IV infusion for labour induction
    - Careful monitoring of fetal heart rate and
    uterine motility essential for dose titration
    - Discontinue immediately in uterine
    hyperactivity or fetal distress
  2. may be given IM in PPH
  3. as a nasal spray to promote milk ejection
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10
Q

What is the function of prostaglandins?

A

induce uterine contractions with varying degrees of pain according to the strength of contractions induced

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11
Q

What medication cocktail is used in early pregnancy to induce abortion?

A

Mifepristone + prostaglandins

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12
Q

Which prostaglandin is preferred for the medical use of induction of late therapeutic abortion and how is it administered?

A

Gemeprost

  • administered vaginally as pessaries
  • It ripens the cervix before surgical abortion, particularly in primigravidas
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13
Q

Describe the use of Misoprostol?

A
  1. to induce labour or medical abortion
    - given by mouth or by vaginal administration
    - Intravaginal use ripens the cervix before
    surgical abortion
  2. alternative in postpartum haemorrhage if
    unresponsive to ergometrine, oxytocin and
    carboprost
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14
Q

What are the uses of Ergot alkaloids?

A

They cause intense tonic myometrial contractions

  1. Prevention and treatment of haemorrhage
  2. Active management of the third stage of labour
    - reduces the risk of postpartum haemorrhage
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15
Q

Which ergot alkaloid can cause intense tonic myometrial contractions?

A

ergometrine

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16
Q

Describe the prevention and treatment of haemorrhage by ergot alkaloids?

A

ergometrine + oxytocin

  • Bleeding due to incomplete abortion can be controlled
  • given intramuscularly
  • the dose is adjusted according to the patient’s condition and blood loss
  • combined are more effective in early pregnancy than either drug alone.
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17
Q

What dosages of ergot alkaloids manage the third stage of labour?

A

Ergometrine 500mcg with oxytocin 5units is given by IM on delivery of the anterior shoulder or, at the latest immediately after the baby is delivered

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18
Q

Describe the dosage of ergot alkaloids used to treat postpartum haemorrhage caused by uterine atony?

A

Ergometrine 250–500micrograms by IV

- use with caution because there is a risk of hypertension

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19
Q

What is the most widely used progesterone receptor anatgonists?

A

mifepristone

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20
Q

What is mifepristone?

A

an anti-progestogenic steroid, sensitises the myometrium to prostaglandin-induced contractions and ripens the cervix

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21
Q

Describe the use of mifepristone?

A

Useful for termination of early pregnancy, when uterine quiescence is dependent principally on progesterone

22
Q

What are the 2 phases of the onset of labour?

A
  1. activation phase

2. stimulation phase

23
Q

Describe the activation phase of the onset of labour?

A
  • The uterus acquires an increased number of receptors for stimulants, particularly oxytocin
  • an increased number of ion channels are formed,
  • an increased number of gap junctions are formed for cell to cell signal transmission
24
Q

Describe the stimulation phase?

A

The myometrium is more responsive and is stimulated by both oxytocin and prostaglandins (produced locally within the uterine muscles)

25
Q

Describe the side effects of oxytocin?

A

Hyper- stimulation caused by Oxytocin
- can be reversed by reducing or discontinuing infusion since oxytocin has short half life or administering beta2 agonists

26
Q

Side effects of oxytocin and prostaglandins?

A

Anaemia, uterine rupture, tachychardia, abdominal pain, vomiting, dyspnoea
- Medical supervision needed

27
Q

Describe the side effects of prostaglandins?

A

Hyperstimulation by PG gel

- insertion into cervix or vagina can cause more problems, saline can be used to wash out the PG

28
Q

Describe the side effects of ergot alkaloids?

A

stroke, hypertension myocardial infarction, palpitations, dyspnoea, abdominal pains

29
Q

What do uterine relaxants do?

A

Postpone premature labour and they are used with the aim of reducing harm to the child.
- there is no satisfactory evidence that the use of these drugs reduce mortality

30
Q

Describe the safe use of uterine relaxants?

A

Prolonged therapy should be avoided since risk to the mother increases after 48 hours and there is a lack of evidence of benefit from further treatment;
- maintenance treatment is therefore not recommended

31
Q

What is atosiban?

A

oxytocin receptor antagonist

32
Q

What is Atosiban used for?

A

the inhibition of uncomplicated premature labour between 24 and 33 weeks of gestation

33
Q

Name the uterine relaxants?

A
  1. beta2 –adrenergic receptor agonist
  2. NSAIDs
  3. magnesium sulphate
  4. calcium channel blockers
34
Q

How do beta 2 agonists work?

A

Uterus is made of smooth muscles therefore beta2 –adrenergic receptor stimulation causes relaxation

35
Q

How do NSAIDs work?

A

inhibit PG synthesis by inhibiting both COX-1 and COX-2 enzymes

36
Q

Why might magnesium sulphate not be favourable in use as a uterine relaxant?

A

mechanism of action is assumed to compete with Ca++ in myometrial cells.

37
Q

How is magnesium sulphate administered?

A

It is given by IV

38
Q

Give an example of a calcium channel blocker used as a uterine relaxant?

A

nicardipine

- by oral route

39
Q

Why is atosiban favoured over beta 2 agonists?

A

has fewer side effects

40
Q

Name beta 2 agonists?

A

ritodrine, salbutamol or terbutaline

41
Q

Describe the use of beta 2 agonists?

A
  • is used for inhibiting uncomplicated premature labour between 24 and 33 weeks of gestation as Atobisan
  • may permit a delay in delivery of at least 48 hours
42
Q

Describe the use of COX inhibitors?

A

Indomethacin also inhibits labour and it can be useful in situations where a beta2 agonist is not appropriate

43
Q

What are the 4 clinical uses of uterine relxants?

A
  1. To prevent or arrest preterm labour.
  2. To reverse inadvertent overstimulation.
  3. To facilitate intrauterine manipulations, such as conversion of a foetus from a breech to a cephalic presentation, surgical procedures, or postpartum replacement of an inverted uterus.
  4. To relieve painful contractions during menstruation - Dysmenorrhea
44
Q

Describe the side effects of beta 2 agonists?

A
  1. Beta2-adrenergic receptor agonists have generalised effects
  2. Beta2 agonists should also be used with caution in diabetes—monitor blood glucose (risk of hyperglycaemia and ketoacidosis, especially with intravenous beta2 agonists)
45
Q

Describe the side effects of COX inhibitors?

A

neonatal complications such as transient impairment of renal function and premature closure of ductus arteriosus

46
Q

Describe the complications of magnesium sulphate?

A

can lead to loss of deep tendon reflexes, respiratory depression and myocardial depression

47
Q

Describe the side effects of calcium channel blockers?

A

generalised fall in blood pressure

48
Q

Describe the dosages of salbutamol?

A

By intravenous infusion, initially 10mcg/ min, rate increased gradually according to response at 10-minute intervals until contractions diminish then increase rate slowly until contractions cease (max. rate 45micrograms/minute)
Maintain rate for 1hour after contractions have stopped, then gradually reduce by 50% every 6hours; then by mouth 4mg every 6–8hours

49
Q

Describe the dosages of atosiban?

A

By IV, initially 6.75mg over 1 minute, then by intravenous infusion 18mg/hour for 3 hours, then 6mg/hour for up to 45 hours; max. duration of treatment 48 hours

50
Q

Describe the dosages of nifedipine?

A

Given initially in a dose of 20mg followed by 10– 20mg ,3–4 times daily adjusted according to uterine activity

Reproductive Pharmacology (4 decks)

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