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3A - Reproductive System > Pharmacology in Pregnancy and Breast Feeding > Flashcards

Pharmacology in Pregnancy and Breast Feeding Flashcards

1
Q

What are the different aspects of pharmacokinetics?

A
  • Absorption
  • Distribution
  • Metabolism
  • Excretion
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2
Q

What are some common reasons for prescribing during pregnancy?

A
  • Hypertension
  • Asthma
  • Epilepsy
  • Migraine
  • Mental health disorders
  • Long term anticoagulant use
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3
Q

What are some absorption changes during pregnancy?

A

Oral route:

  • Morning sickness
  • Decrease in gastric emptying and gut motility

Intramuscular route (IM):

  • Blood flow increase, so absorption enhanced

Inhalation:

  • Increased cardiac output and decreased tidal volume may increase absorption
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4
Q

What are some distribution changes during pregnancy?

A
  • Increase in plasma volume and fat
    • Increases volume of distribution
  • Greater dilution of plasma
    • Decrease relative amount of plasma proteins so increase fraction of free drug
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5
Q

What are some metabolism changes during pregnancy?

A

Oestrogen and progestogens can induce or inhibit liver P450 enzymes, increasing or reducing metabolism

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6
Q

What are some excretion changes during pregnancy?

A

GFR increased in pregnancy by 50%, causing increased excretion of many drugs:

  • Can reduce plasma concentration and necessitate an increase in dose
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7
Q

What is pharmacodynamics?

A

Drug effect on body

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8
Q

What is pharmacokinetics?

A

Bodies effect on drugs

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9
Q

What pharmacodynamic changes can occur during pregnancy?

A
  • Site of drug action
  • Receptor response to drugs
  • Efficacy may be difference
  • Adverse effects may be different
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10
Q

What do drugs need to cross before reaching the foetus?

A

The placenta, which most drugs can

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11
Q

What are some factors affecting placental drug transfer and drug effect on the foetus?

A
  • Drug physiochemical properties
  • Rate at which drug crosses placenta and amount reaching foetus
  • Duration of drug exposure
  • Distribution in different foetal tissues
  • Stage of placental and foetal development
  • Effect of drugs when used in combination
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12
Q

What does placental transfer depend on?

A
  • Molecular weight
    • Smaller sizes cross more easily
  • Polarity
    • Unionised molecules cross more readily
  • Lipid solubility
    • Lipid soluble drugs will cross
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13
Q

How is distribution different in a foetus?

A
  • Circulation is different
    • Such as umbilical vein to liver
  • Less protein binding than adults therefore more free drug available
  • Little fat, so distribution different
  • Relatively more blood flow to brain
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14
Q

How is metabolism different in a foetus?

A
  • Reduced enzyme activity, although increases with gestation
  • Different P450 isoenzymes to adults
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15
Q

How is excretion different in a foetus?

A
  • Excretion is into amniotic fluid, which foetus then swallows leading to recirculation
  • Drugs and metabolites can accumulate in amniotic fluid
  • Placenta not functioning at delivery so can be issues with excretory function
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16
Q

Is there a lot of guidance about prescribing during pregnancy?

A

Due to lack of research there is uncertainty around dosing, some information is available for some drug groups:

  • Anti-convulsants
  • Anti-hypertensives
  • Analgesics
  • Antibacterials
17
Q

What are the principles for prescribing for woman of child bearing age?

A
  • Always consider possibility of pregnancy
  • Warn of possible risks
  • When treating conditions, advise woman to attend before getting pregnant
  • Discuss contraception
18
Q

What are the principles of prescribing during pregnancy?

A
  • Try non-pharmacological measures first
  • Use safest drug, avoiding new drugs unless proven safe
  • Use lowest effective dose
  • Avoid in first 10 weeks of pregnancy
  • Consider stopping or reducing drug before delivery
19
Q

What are the two major risks of taking drugs during pregnancy?

A
  • Teratogenicity (mostly occurs during first trimester)
  • Fetotoxicity (most occurs during second and third trimester)
20
Q

When does teratogenecity and fetotoxicity mostly occur?

A

Teratogenecity - first trimester

Fetotoxicity - second and third trimester

21
Q

What are teratogenic drugs?

A

Teratogen is an agent that can disturb the development of the embryo or foetus

22
Q

When is the highest risk of teratogenecity?

A

During organogenesis (weeks 3-8)

23
Q

Through what mechanisms do teratogenic drugs act?

A
  • Folate antagonism
    • Key process in DNA formation
    • 2 groups of drugs affect folate metabolism
      • Block conversion of folate to THF by binding irreversibly to the enzyme
      • Block other enzymes in folate pathway
    • Tends to result in neural tube, oro-facial or limb defects
  • Neural crest cell disruption
    • Associated with retinoid drugs
    • Problems includes aortic arch anomalies, ventricular septal defects, craniofacial malformations, oesophageal atresia, pharyngeal gland abnormalities
  • Endocrine disruption
  • Oxidative stress
  • Vascular disruption
  • Specific receptor or enzyme mediated teratogenesis
24
Q

What is folate key for?

A

DNA formation

25
Q

How do the 2 groups of drugs that block folate metabolism work?

A
  • Block conversion of folate to THF by binding irreversibly to the enzyme
  • Block other enzymes in folate pathway
26
Q

What kind of defects does folate metabolism tend to cause?

A
  • Tends to result in neural tube, oro-facial or limb defects
27
Q

What drug is neural crest disruption associated with?

A
  • Associated with retinoid drugs
28
Q

What kinds of problems does neural crest disruption cause?

A
  • Problems includes aortic arch anomalies, ventricular septal defects, craniofacial malformations, oesophageal atresia, pharyngeal gland abnormalities
29
Q

What are some examples of known teratogens?

A
  • Anticonvulsants
    • Neural tube defects
  • Anticoagulants
    • Haemorrhage
  • Antihypertensive agents
    • Renal damage and restrict normal growth
  • NSAIDs
    • Premature closure of ductus arteriosus
  • Alcohol
    • Foetal alcohol syndrome
  • Retinoids
    • Ear, CNS, cardiovascular and skeletal disorders
30
Q

What are some possible issues due to fetotoxicity?

A
  • Growth retardation
  • Structural malformation
  • Foetal death
  • Functional impairment
  • Carcinonogenesis
31
Q

Why is taking drugs during lactation an issue?

A

Almost all drugs mother takes will be present in breast milk

32
Q

Describe the strategy of drug prescription during breast feeding?

A
  • Is drug necessary
  • If yes, is it safest option
  • Non-pharmacological strategies
  • Avoid drugs with long half life
  • Use drugs that are highly protein bound
33
Q

What are some examples of drugs that should be avoided in breastfeeding?

A
  • Cytotoxics
  • Immunosuppresants
  • Anti-convulsants
  • Drugs of abuse
  • Amiodarone
  • Lithium
  • Radio-iodine

3A - Reproductive System (34 decks)

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