HNM322 Drugs

Question 1

Betamethasone

Answer 1

Indication: birth 24-34 weeks.

MOA: corticosteroid that aids lung development.

Dose: 2x11.4mg doses 24 hours apart.

Contraindicated in chorioamnionitis

Question 2

Magnesium Sulfate

Answer 2

Indication: birth 24-30 weeks or pre-eclamptic seizures.

MOA: Neuroprotective

Dose:
* Loading 4mg over 20 minutes
* Maintenance 1g/hr until 24hrs post birth

*Take 4 hourly Mg level
*10% calcium gluconate injection available for hypermagnesemia
* IDC - hourly output (25mL/hr)
*Cont CTG

Question 3

Nifedipine

Answer 3

Indication: pre-term labour.

MOA: short term tocolytic, calcium channel antagonist that inhibits smooth muscle contraction.

Dose:
* Loading 10mg/20 mins (3x repeat dose 30 minutes apart when contractions persist)
* Maintenance 20mg every 6 hrs for 48 hrs

Headache, flushing, peripheral oedema, constipation.

Question 4

Terbutaline/Salbutamol

Answer 4

Indication: pre-term labour, hypertonus.

MOA: Beta-2 agonist, smooth muscle relaxation, tocolytic.

Dose: 250mcg single dose.

Tremor, palpitations, headache.

Question 5

GTN

Answer 5

Indication: pre-term labour, hypertonus.

MOA: exogenous nitric oxide, inhibits uterine contractions.

Dose: 400mcg (repeat at 5 minutes, max 2 doses).

Question 6

Labetalol

Answer 6

Indication: HTN

MOA: beta-blocker, reduce cardiac contractility and BP.

Dose:
* Acute 20-80mg IV over 2min.
* Maintenance: 100-400mg every 8 hours.

Bradycardia, hypotension, fetal bradycardia, bronchospasm.

Question 7

Hydralazine

Answer 7

Indication: HTN

MOA: vasodilator, lower BP.

Dose:
* Initial 5-10mg.
* Maintenance 25-50mg TDS.

Flushing, headache, nausea, lupus-like syndrome, tachycardia, fluid retention.

Question 8

Methyldopa

Answer 8

Indication: HTN

MOA: alpha-2 adrenoreceptor agonist, lower BP.

Dose: 250-750mg TDS

Crosses the placenta, may cause fetal hypotension. Rebound hypertension.

Question 9

Anti-D

Answer 9

Indication: negative maternal blood group.

MOA: mops up blood in maternal circulation.

Dose: 625 IU neutralises 6mL of fetal blood.

• Routine 28, 34, post birth
• Sensitising event <12wks 250 IU
• Sensitising event >12 wks 625 IU

Question 10

GBS Prophylaxis/PPROM

Answer 10

Benzylpenicillin
* 3g IV loading dose.
* 1.8g IV every 4hrs for 48 hrs or delivery.

Cephazolin if penicillin allergy
* 2g IV loading dose.
* 1g IV every 8 hrs for 48 hrs or delivery.

Clindamycin if penicillin anaphylaxis.
* 900 mg IV in 50-100 ml over at least 20 minutes every eight hours, for 48 hours or delivery.

Erythromycin 250mg QID for 10 days or delivery.

Question 11

Chorioamnionitis

Answer 11

Loading dose: Ampicillin 2g IV.

If allergic to penicillin Clindamycin IV 600mg/hrs.

Maintenance: Ampicillin IV 1g/6hrs + Gentamicin IV 5mg/kg daily + Metronidazole IV 500mg/12hrs.

Question 12

Hyperemesis Gravidarum

Answer 12

Pyridoxine (B6)
* 50mg QID or
* 200mg nocte

Prochlorperazine (Stemitil) = atypical antipsychotic
* 5-10mg QID or
* 25mg daily

Doxylamine (Restavite) = H1 (histamine 1) antagonist
* 12.5mg nocte
* very sedating

Promethazine (Phenergan) = antagonist of histamine H1, post-synaptic dopamine, alpha adrenergic, muscarinic, and NMDA receptors
* 10-25mg TDS
* very sedating

Metoclopramide (Maxalon) = dopamine antagonist
* 10mg TDS
* max 5 days

Ondansetron = 5HT3 antagonist
* 4-8mg TDS