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Year 3 Clinical > Prescribing in Pregnancy > Flashcards

Prescribing in Pregnancy Flashcards

1
Q

Major principles of prescribing in pregnancy?

A

No drug is safe beyond all doubt in early pregnancy

Consider non-drug alternatives, e.g: physiotherapy instead of NSAIDs, CBT instead of anti-depressants

If benefit outweighs risk, prescribe the drug (at the lowest effective dose, for the shortest period)

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2
Q

Licensing of drugs in pregnancy?

A

Most drugs are not licensed for use in pregnancy, i.e: they are usually prescribed outwith their licensed uses

The fact that it is being used for an unlicensed indication, its benefits vs risks, etc, must all be explained to the woman before gaining consent; this must be carefully documented

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3
Q

Occurrence of medication use during pregnancy?

A

Most women take drugs during pregnancy, e.g: folic acid, iron, antibiotics, painkillers

NOTE - this includes self-medication, e.g: NSAIDs, St. John’s wort, other herbal preparations

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4
Q

Which drugs cross the placenta and which do not?

A

Most drugs cross the placenta, except large molecular weight drugs, like heparin

Small, lipid-soluble (lipophilic) drugs cross the placenta faster

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5
Q

Define pharmacokinetics?

A

What the body does to a drug after it is taken / administered:

  1. Absorption
  2. Distribution
  3. Metabolism
  4. Elimination
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6
Q

Factors affecting pharmacokinetics of a drug during pregnancy?

A

Increased plasma volume and fat stores, as the Vd increases (total amount of drug / Cp)

Decreased protein bindings results in increased free drug

Increased liver metabolism of some drugs, e.g: phenytoin

Elimination of renally excreted drugs increases, so the GFR increases

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7
Q

Define pharmacodynamics?

A

What the drug does to the body

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8
Q

Changes in pharmacodynamics during pregnancy?

A

No significant change, although pregnant women may be more sensitive to some drugs, e.g: hypotension may occur with anti-hypertensive in the 2nd trimester

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9
Q

Considerations before prescribing to any woman of childbearing age?

A

Are they pregnant?

Are they planning a pregnancy?

Could they become pregnant?

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10
Q

Pre-conceptual advice that should be given?

A

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

Counselling regarding chronic conditions, e.g: epilepsy, diabetes, hypertension; review whether drug therapy is necessary and, if it is, optimise their therapy, choosing the safest drugs

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11
Q

Risks assoc. with drug use during the 1st trimester?

A

Organogenesis occurs during early pregnancy

Risk of early miscarriage

NOTE - avoid drugs, if at all possible, unless the maternal benefit outweigh risk to the foetus

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12
Q

Period of greatest teratogenic risk during pregnancy?

A

4th-11th week

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13
Q

Common teratogenic drugs?

A

ACEIs / ARBs - renal hypoplasia

Androgens - virilisation of female foetus

AEDs - cardiac, facial, limb defects and NTDs

Cytotoxics - multiple defects and abortion

Lithium - CV defects

Methotrexate - skeletal defects

Retinoids - ear, CV and skeletal defects

Warfarin - limb and facial defects

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14
Q

Risks of medication use during the 2nd &3rd trimesters?

A

During this period, there is growth of the foetus

Function development can be affected, leading to:
• Intellectual impairment
• Behavioural abnormalities

There can be toxic effects on foetal tissue

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15
Q

Risks of medication use around term?

A

Adverse effects on labour:
• Progress of labour
• Adaptation of foetal circulation, e.g: may have premature closure of the ductus arteriosus
• Suppression of foetal system, e.g: opiates can cause respiratory depression
• Bleeding, e.g: warfarin

Adverse effects on baby after delivery:
• Withdrawal syndrome, e.g: opiates, SSRIs
• Sedation

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16
Q

Example of drug that, when used during pregnancy, showed delayed effects?

A

Diethylstilbestrol was used to prevent recurrent miscarriage, which it did not achieve

Caused:
• Vaginal adenocarcinoma in girls aged 15-20 years, whose mothers were exposed to diethylstilbestrol
• Urological malignancy in boys

17
Q

Potential consequences of not using asthma inhalers during pregnancy?

A

Many women avoid using their asthma inhalers in pregnancy; this can lead to an asthma attack and foetal hypoxia

18
Q

Pregnancy risks assoc. with epilepsy?

A

Incidence of congenital malformations is higher in untreated women with epilepsy that in women without epilepsy

Increased seizures in 10% of women due to:
• Non-compliance
• Changes in plasma conc. of drugs, e.g: persistent vomiting leads to decreased absorption OR their may be increased clearance

Frequent seizures during pregnancy are assoc. with:
• Lower verbal IQ in child
• Hypoxia
• Bradycardia
• Antenatal death
• Maternal death
19
Q

Principles of prescribing for epilepsy during pregnancy?

A

Benefits outweigh risks in most cases, although AEDs do increase the risk of congenital malformations (20-30% increase with 4 drugs); MONOTHERAPY is preferred

NOTE - most babies born to women taking AEDs will not have congenital malformations

AVOID sodium valproate and phenytoin

Prescribe FOLIC ACID 5MG daily

20
Q

Principles of prescribing for diabetes during pregnancy?

A

Poor control increases the risk of congenital malformations and IUFD

Insulin and metformin are considered safe but sulfonylureas are not (convert to insulin)

Drug requirements change during pregnancy

21
Q

Principles of prescribing for hypertension during pregnancy?

A

BP falls during the 2nd trimester

If treatment is required:
• 1st line - labetalol (NOTE - β-blockers may inhibit foetal growth in late pregnancy)
• 2nd line - methyldopa
• 3rd line - Nifedipine MR

Avoid ACEIs / ARBs

22
Q

Common acute problems during pregnancy, for which prescribing may be required?

A

N&V - cyclizine

UTI - follow local guidelines:
• Nitrofurantoin
• Cefalexin
• 3rd trimester, trimethoprim

Pain - paracetamol

Heartburn - antacids

23
Q

Risk of VTE during pregnancy?

A

Risk of VTE is 10x higher, compared to non-pregnancy

VTE is the leading cause of maternal death in pregnancy

24
Q

Which pregnant women should be assessed for risk of VTE?

A

All pregnant women

25
Q

Advice for pregnant women, for prevention of VTE?

A

Regardless of risk, all women who are pregnant, in labour or in the puerperium should be encouraged to MOBILISE and be adequately HYDRATED

26
Q

Which pregnant women should receive thromboprophylaxis and what is this?

A 
2 or more risk factors, e.g:
• Obesity
• Age >35 years
• Smoking
• Para >3
• Previous DVT
• Caesarian delivery

Should receive LMWH, which should be continued at delivery and up to 7 days post-partum

27
Q

Treatment of VTE in pregnancy?

A

Treat suspected or established DVT or PE with therapeutic dose of LMWH

28
Q

Why is warfarin avoided during pregnancy?

A

Avoid warfarin in early pregnancy, as it is teratogenic

Avoid warfain in late pregnancy, as there is a risk of haemorrhage during delivery

29
Q

Which drugs enter breastmilk?

A

Most drugs, esp. small molecules and lipophilic drugs

However, few drugs enter in sufficient quantities to cause problems

30
Q

Factors affecting drugs entering the breastmilk?

A

Feeding patterns can affect amounts:
• Foremilk - protein-rich
• Hindmilk - higher fat content
So, longer feeds have higher amounts of fat-soluble drugs in the milk

Immature metabolism - drugs may accumulate

Some drugs are actively conc. in breast milk, e.g: phenobarbitone (old-fashioned AED)

31
Q

Problems assoc. with specific drugs during pregnancy?

A

Amiodarone - neonatal hypothyroidism

Cytotoxics - bone marrow suppression

Benzodiazepines - drowsiness

Bromocriptine - suppresses lactation

32
Q

Helpful resources when making prescribing decisions?

A

BNF

UK Drugs In Lactation Advisory Service (UKDILAS)

UK Teratology Information Service

33
Q

What should be done in the following case?

Essential hypertension, with a BP of 164/102 mmHg after lifestyle measures; she is on no regular medication.

She is planning pregnancy in the next year and is worried about whether she will have problems due to her BP .

A

Encourage further lifestyle improvement

Counsel on risks and benefits of treating hypertension in pregnancy

Options:
1. No treatment but close monitoring of BP in pregnancy, esp. after the 2nd trimester
2. Start treatment with a drug thought to be safe during pregnancy:
• Labetalol
• Methyldopa
• Nifedipine MR

34
Q

What should be done in the following case?

A woman who is 28 weeks pregnant presents with a swollen right leg and the USS confirms an extensive right DVT.

A

Therapeutic dose of LMWH, continued throughout pregnancy

NOTE - women can be taught to self-inject LMWH at home

35
Q

Which antibiotic given during pregnancy or in early childhood can cause the appearance of stained bones and teeth?

A

Tetracycline (it is also avoided in children up to 12 years of age)

36
Q

Which drugs taken in excess, in early pregnancy, could have caused this appearance?

ADD IMAGE

A

Alcohol (causes foetal alcohol syndrome)

37
Q

Which AED is particularly associated with cleft lip and palate?

A

Phenytoin

38
Q

Which drug taken during pregnancy can cause this problem in female offspring?

ADD IMAGE

A

Diethylstilbestrol (causes vaginal adenocarcinoma)

39
Q

Which AED is part. assoc. with the spina bifida and anencephaly?

A

Sodium valproate (causes NTDs)

Year 3 Clinical (100 decks)

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