L7 Drugs in Pregnancy and Lactation

Teratogenesis - Pregnancy phases and risk"
• Pre-embryonic (conception to 17 days) - All or nothing, i.e. if many cells damaged the pregnancy will spontaneously ❌
• Embryonic (Day 18-55) - Cells are differentiating and major organs forming, embryo is most ❌ to teratogens
• Foetal (day 56 to birth) - Some structures still developing (cerebral cortex, renal glomeruli) - prone to
❌. Deafness can still occur in this period

Non-teratogenic harm to the foetus:
• Anything that causes ❌ of the placental vasculature may harm the foetus
• Spontaneous abortions (e.g. ❌)
• Intra-uterine growth retardation
• Prematurity and still-births (❌)
• Neonatal CNS depression or withdrawal

Physiologic changes during pregnancy can affect the pharmacokinetics/pharmacodynamics of drugs:
• Changes in total body ❌ and body ❌ composition
• Prolonged gastrointestinal transit time which can affect the ❌ of drugs
• Expanded plasma volume, more extracellular fluid & total body water which may increase the ❌ of distribution for ❌ drugs

ADEC Pregnancy Categories (Australia) does not take into account ❌ reactions in the neonate to a medicine that crosses the placenta, or in cases of ❌, occupational exposure etc.

Factors that determine transfer into breast milk:
• Drug concentrations in the maternal plasma; some drugs are poorly absorbed into the maternal ❌
• Drug ❌ (Note that fat is a small proportion of milk)
• Drug protein binding
• Milk pH (Milk pH = 7.0–7.2. More acidic than plasma (pH = 7.4) some ion trapping)
• Molecular size – drugs that are <500 Da.

• Most drugs transfer into milk(rare exceptions: ❌.)
• Most drugs transfer by ❌ diffusion (unionised, unbound drug)
• Extent of transfer depends on properties of the drug, blood and breast milk

• Decreased milk production = dopamine ❌ e.g. bromocriptine, ❌-containing contraception
• Increased milk production = dopamine ❌ e.g. domperidone, SSRIs, opioids