Drugs in Obs and Gynae

Question 1

What does tocolysis mean?

Answer 1

The administration of drugs to reduce uterine activity

Question 2

What are the factors that determine whether tocolysis is necessary in a women is is going into preterm labour?

Answer 2

Cervical dilatation

The need to administer steroids and allow time for them to be effective

Need for in utero transfer (breech)

Question 3

What are the different drugs that can be used as tocolytics, drugs that try and stop contractions in women who have gone into preterm labour? For each class give an example that is used.

Answer 3

Oxytocin receptor antagonists - atosiban

Calcium channel blockers - nifedipine (not licenced in the UK)

Beta agonists - salbutamol, ritodrine, terbutaline (IV)

NSAIDs (prostaglandin inhibitors) - indomethacin

Nitric oxide donors - GTN (transdermal patch)

Question 4

What are the potential side effects of oxytocin receptor antagonists, used as tocolytics?

Answer 4

8% of women experience headaches

Question 5

What are the potential side effects of calcium channel blockers such as nifedipine when used as tocolytics?

Answer 5

Headache
Flushing
Tremor

Question 6

What are the potential side effects of beta agonists such as salbutamol when used as tocolytics?

Answer 6

Side effects are very common (80% of women):

Tachycardia (both mother and fetus)
Headache
Tremor
Hyperglycaemia
Hypokalaemia
Pulmonary oedema
MI

Question 7

What are the potential side effects of NSAIDs such as indomethacin when used as tocolytics?

Answer 7

Mother:
Heartburn
Nausea

Fetus:
Premature closure of ductus arteriosus
Reduced renal function causing oligohydramnios

Question 8

What are the contraindications for the use of tocolytics?

Answer 8

Maternal illness that would be helped by delivery (eg pre-eclampsia)

Evidence of fetal distress

Chorioamnionitis - intra-amniotic infection

Significant vaginal bleeding, particularly if abruption is suspected

Already ruptured membranes

Question 9

Should all women who go into preterm labour be given antibiotics?

Answer 9

Those women whose membrane has ruptured before term should have prophylactic erythromycin.

If membrane is intact, the mother should be screened for infection with vaginal and cervical swabs and blood cultures if pyrexial) and only given antibiotics if there are signs of infection.