Prescribing in Pregnancy and Substance Misuse

Question 1

Are ACE inhibitors safe to prescribe in pregnancy?

Answer 1

No

• Contraindicated across pregnancy
• Cause oligohydramnios, hypotension, renal failure and intra-uterine death

Question 2

Are beta blockers safe to prescribe in pregnancy?

Answer 2

Yes

• Indicated in hypertension, Labetalol is the first line
• Do not reduce the risk of pre-eclampsia
• In pre-eclampsia, methyldopa is used as a second line agent
• Can cause foetal bradycardia and IUGR

Question 3

Are antibiotics safe to prescribe in pregnancy?

Answer 3

Antibiotics to avoid:

• Quinolones
• Aminoglycosides
• High dose metronidazole
• Trimethoprim (anti-folate)
• Nitrofurantoin (neonatal haemolysis)
• Tetracyclines (stains bones and teeth)

Question 4

Are antibiotics safe to prescribe in breastfeeding?

Answer 4

• Penicillins and cephalosporins are drugs of choice

Avoid:
- Metronidazole and quinolones

Question 5

Are anticoagulants safe to prescribe in pregnancy?

Answer 5

• Heparin has no affect

Avoid:
- Oral anticoagulants cross the placenta and have a high abortion rate in the first trimester

Question 6

Are NSAIDs safe to prescribe in pregnancy?

Answer 6

They can prolong labour and gestation

They can cause premature closure of the ductus arteriosus

Question 7

Are anti-epileptic drugs safe to prescribe in pregnancy?

Answer 7

Carbamazepine:
- While this is the safest AED, one should aim not to prescribe it in pregnancy

Sodium Valproate

• Not advised
• If given, give the lowest therapeutic dose, and supplement with folate

Lamotrigine
- Not advised in breastfeeding as it can cause Stevens-Johnson syndrome in infants

Question 8

Are antidepressants safe to prescribe in pregnancy?

Answer 8

One can only prescribe tri-cyclic antidepressants and Fluoxetine

Question 9

Are benzodiazepines safe to prescribe in pregnancy?

Answer 9

No, they should be avoided

Question 10

Is lithium safe to prescribe in pregnancy?

Answer 10

No, is teratogenic

Question 11

Is warfarin safe to prescribe in pregnancy?

Answer 11

No, is teratogenic

Question 12

Are diuretics safe to prescribe in pregnancy?

Answer 12

Can cause neonatal thrombocytopaenia

Question 13

Is vitamin A (retinoids) safe to prescribe in pregnancy?

Answer 13

No, is teratogenic

Question 14

Are barbiturates safe to prescribe in pregnancy?

Answer 14

They can lead to congenital malformations

Question 15

Are anxiolytics safe to prescribe in pregnancy?

Answer 15

They can cause respiratory depression in the foetus and the mother

Question 16

Describe the physiological changes to pharmacodynamics in the pregnant woman

Answer 16

Absorption can reduce with nausea and vomiting

Distribution can reduce with an increased plasma volume and decreased plasma binding

Metabolism increases with the induction of cytochrome P450

Excretion is increased with a 50% increase in GFR

Question 17

What is the epidemiology surrounding substance abuse in pregnancy

Answer 17

There are approximately 6000 births a year from substance abusers. A full MDT approach is necessary as often the financial, psychological, social and domestic problems out weigh the medical concerns.

Question 18

What are some common problems faced by drug addicts?

Answer 18

• Social: housing, crime, other children
• Addictions: alcohol, smoking
• Malnutrition: iron, vitamin B and C
• Viral infections: HIV, Hep B
• Foetal and neonatal risks

Question 19

Describe the use of opiates in pregnancy

Answer 19

It is usually heroin use but many take it in combination with cocaine or crack cocaine.

It is important not to reduce the opiate dose too rapidly as sudden detoxification can be dangerous for the baby, especially in the third trimester. The principle is to administer the lowest effective dose of methadone liquid, over three doses.

Question 20

Describe the use of alcohol in pregnancy

Answer 20

The advice is to not have any alcohol at all.

Large alcohol doses are related to FGR and foetal alcohol syndrome.

A common problem is low adherence to medication, and defaulting appointments. Close work with social workers is necessary to optimise outcomes for mother and baby.

Foetal alcohol syndrome:

• Microcephaly
• SGA
• Small eyes, thin upper lip
• Cerebral palsy
• Intellectual disability and neurological deficits
• Irreversible damage so should try to be prevented

Question 21

Describe smoking in pregnancy

Answer 21

This reduced placental perfusion which contributes to SGA and FGR; the overall weight difference would be 15g multiplied by the average number of cigarettes a day. There is a higher risk of placental abruption.

Smoking less than 5 cigarettes a day has barely any effects and quitting before 15 weeks is the same as quitting before pregnancy.

Nicotine patches are safe to use in pregnancy.