Prescribing in Pregnancy Flashcards

1
Q

At what gestation age do most women do their first scan?

A

12 weeks

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2
Q

Approach to treating pregnant women

A

Consider non drug alternatives

  • physio instead of NSAID
  • CBT instead of anti-depressant

Prescribe if benefit > risk

Most drugs are not licensed for use in pregnancy
- prescribe out with license

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3
Q

What are the most commonly used drugs during pregnancy?

A

Painkillers ~12%
Antibiotics ~11%
Antacids ~8%
(Also folic acid and iron)

Remember self-medication

  • NSAID
  • St John’s wort - antidepressant
  • Other herbal preparations
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4
Q

Which drugs cross placenta?

A

Most drugs cross placenta

  • Except large molecular weight
    ex. Heparin

Small, lipid-soluble drugs
- Cross more quickly

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5
Q

Absorption and Pregnancy

A

Affected by morning sickness

Oral drugs come straight back up

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6
Q

Distribution and pregnancy

A

Increased plasma volume and fat stores
- Volume of distribution increases

Decreased protein binding
- Increased free drug

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7
Q

Metabolism and pregnancy

A

Increased liver metabolis of some drugs ex. phenytoin

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8
Q

Elimination and pregnancy

A

Increased in renally excreted drugs

- Increased GFR

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9
Q

Drugs to be monitored during pregnancy

A

Lithium
Digoxin

check concentrations and alter dose during pregnancy and after delivery

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10
Q

Pharmacodynmics and pregnancy

A

No significant changes

  • Pregnant women may be more sensitive to some drugs
  • hypotension with antihypertensives in 2nd trimester
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11
Q

Prescribing during pre-conception

A

Any woman of childbearing age

  • Are they pregnant?
  • Are they planning a pregnancy?
  • Could they become pregnant?

Folic acid 400mcg daily for 3 months prior and first 3 months of pregnancy

Counselling re chronic conditions
- Epilepsy, diabetes, hypertension

Optimise therapy to choose safest drugs

Review whether drug therapy necessary

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12
Q

Why should drugs be avoided at all cost during 1st trimester (unless maternal benefit > foetal risk)?

A

Risk of early miscarriage

Organogenesis of foetus

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13
Q

Which period has the greatest teratogenic risk?

A

4th to 11th week

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14
Q

List the teratogenic drugs

A

ACE inhibitors/ARB - Renal hypoplasia

Androgens- Virilisation of female foetus

Anti-epileptics - Cardiac, facial, limb, neural tube defects

Cytotoxics - Multiple defects, abortion

Lithium- Cardiovascular defects

Methotrexate - Skeletal defects

Retinoids - Ear, cardiovascular, skeletal defects

Warfarin- Limb and facial defects

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15
Q

2nd + 3rd trimesters

A
Growth of foetus
Functional development
- Intellectual impairment
- Behavioural abnormalities
Toxic effects on foetal tissue
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16
Q

Valproate and pregnancy

A

Contraindicated

Need to sign a document to declare they have been educated on the effects if they require this treatmet

17
Q

Around term

A

Adverse effects on labour

  • Progress of labour
  • Adaptation of foetal circulation
    • Premature closure of ductus arteriosus
  • Suppression of foetal systems
    • Opiates – respiratory depression
  • Bleeding
    • Warfarin

Adverse effects on baby after delivery

  • Withdrawal syndrome
    • opiates, SSRI
  • Sedation
18
Q

Chronic conditions and pregnancy

A

Need to discuss risk/benefit balance with patient
- Ideally pre-conception
Compliance with medication may be poor

19
Q

Anti-epileptic treatment to avoid during pregnancy

A

Valproate

Phenytoin

20
Q

Why do women need to continue anti-epileptic treatment during pregnancy?

A

Anti-epileptics increase risk of congenital malformations

  • 20-30% risk if on 4 drugs
  • Monotherapy preferred

96% of babies born to women taking anti-epileptics will not have major congenital malformations

Benefits of treatment outweigh risks in most cases

21
Q

Managing diabetic pregnant mothers

A

Insulin thought to be safe

Requirements change during pregnancy

Poor control increases risk of congenital malformations and intra-uterine death

Sulfonylureas not safe
- Convert to insulin

22
Q

Managing BP during pregnancy

A

BP falls during 2nd trimester

If need to treat, use one of:

  • Labetalol
  • Methyldopa (avoid in mothres prone to depression)
  • (Nifedipine MR)

Avoid ACE inhibitors / ARB

Beta blockers may inhibit foetal growth in late pregnancy

23
Q

Common acute problems and their management

A

Nausea and vomiting
- Cyclizine safest

UTI – follow local guidelines
Nitrofurantoin, cefalexin, (3rd trimester – trimethoprim)

Pain
- Paracetamol

Heartburn
- Antacids

24
Q

Pregnant women are at increased risk for which CV condition?

A

10 fold risk of VTE
Leading cause of maternal death in pregnancy
All pregnant women should be assessed for risk

25
Q

Prevention of VTE in pregnancy

A

Those with significant risk factors should receive thromboprophylaxis with LMWH

  • 2 or more risk factors eg obesity, age>35yrs, smoking, para >3, previous DVT, Caesarean delivery
  • at delivery and up to 7 days post-partum
26
Q

Treatment of venous thromboembolism in pregnancy

A

Treat suspected or established DVT or PE with therapeutic dose LMWH

  • Avoid warfarin in early pregnancy
    • Teratogenic

Avoid warfarin in late pregnancy
- Risk of haemorrhage during delivery

27
Q

Breastfeeding and medication

A

Most drugs enter breast milk, especially

  • Small molecules
  • Fat soluble (lipophilic) drugs

Few enter in sufficient quantities to cause a problem

Some drugs are actively concentrated in breast milk
Eg phenobarbitone – suckling difficulties

28
Q

What are the feeding patterns and how it affects the amount of drugs in breastmilk?

A

Foremilk – protein rich
Hindmilk – higher fat content

Longer feeds, higher amounts of fat soluble drugs in milk

29
Q

Drugs contraindicated in breastfeeding

A

Amiodarone – neonatal hypothyroidism

Cytotoxics – bone marrow suppression

Benzodiazepines- drowsiness

Bromocriptine – suppresses lactation

30
Q

Guidelines for prescribing during pregnancy

A
  1. BNF

2. UK Drugs in Lactation Advisory Service (UKDILAS)

31
Q
Case: 
Essential hypertension
BP 164/102mmHg after lifestyle measures
- No regular medication
- Planning pregnancy in next year

Worried about whether she will have problems due to her BP if she gets pregnant

How do you manage this pateint?

A

Counsel about risks and benefits of treating hypertension in pregnancy

Encourage further lifestyle improvement

Options:

  • No treatment but monitor BP closely in pregnancy especially after 2nd trimester
  • Start treatment with drug thought to be safe in pregnancy
    • Labetalol or methyldopa
    • (Nifedipine MR)
32
Q

Which antibiotic given during pregnancy or in early childhood can cause staining of teeth?

A

Tetracycline

33
Q

Which ‘drug’ taken in excess in early pregnancy could cause deformed facial features?

A

Alcohol - Fetal alcohol syndrome

34
Q

Which antiepileptic drug is particularly associated with cleft palate?

A

Phenytoin

35
Q

Which drug taken during pregnancy can cause vaginal carcinoma in female offspring?

A

Diethylstilbesterol

36
Q

Which antiepileptic drug is particularly associated with spina bifida and anencephaly

A

Valproate

37
Q

What is the danger of epilepsy during pregnancy?

A

Incidence of congenital malformations higher in untreated women with epilepsy than women without epilepsy

38
Q

Why are there increased seizures in 10% of women during pregnancy?

A

Non-compliance
Changes in plasma concentrations of drugs
- Persistent vomiting
- Increased clearance

39
Q

What is the consequence of frequent seizures during pregnancy?

A
lower verbal IQ in child
hypoxia
bradycardia
antenatal death
maternal death