Medicines And Lactation (1.4) Flashcards
What are some the risks of giving medicines to infants and lactating mother?
Risks to infants
- Majority of drugs will transfer into breast milk
- Only low levels are usually received by breastfed infants –> henece only few drugs pose significant threat
Risks to lactating mothers
- Some drugs may reduce milk supply and affect breastfeeding performance (i.e. exclusivity, duration and success)
- Need to ensure mothers who need to receive pharmacotherapy are able to do so
Describe the control of lactation by prolactin (4 step process)?
Does D2 antagonist stimulate lactation?
- Stimulation by suckling or infant cries
- Dopaminergic neurones –> D2 receptors
- Prolactin release from anterior pituitary
- Prolactin secretion increases lactation?
Yes, D2 antagonist does stimulate lactation while D2 agonist inhibits lactation
Describe the control of lactation by oxytocin? (4 step proces)
- Stimulation by suckling/infant cries –> send efferent impulses to hypothalmus
- Stimulation of posterior pituitary to release oxytocin
- Oxytocin stimulations contraction of myoepithelial cells
- Milk ejection = “Let Down”
What is the structure of the milk secretion unit?
What are some of the factors affecting drug distribution into milk?
- Oil: water partition coefficient
- Concentration in blood (passive diffusion gradeint)
- Fat content of milk (co-solubility for some drugs)
- Inoisation status of drug; acid or base; pkA and pH of milk
- Extent of protein binding of drug in plasma and milk
- Molecular weight of drug (small molecules like heparin does not enter)
- Active efflux transport
What is the milk:plasma distribution ratio? What does it measure? Does a lower M:P mean the drug is safer to use in lactation?
- Equilibrium distribution between milk and plasma
- M:P ratio measures the extent of drug trasnfer into milk
- High M:P doesnt mean (most of the time) high infant expsoure
M:P has no direct relavance to drug safety in lactation
Describe the passage of drugs to infant
- Drug entry –> maternal plasma (some clearance) -> -< into breast milk –> orally ingested by infant –> now in infant plasma (potential adverse effects) –> clearance
What are some factors affecting infant exposure?
- Amount of drugs ingested by infant (concentration in milk, daily milk intake)
- Oral bioavailablity in infant (infant stomach acidity dentatures some drugs)
- Age of infants (preterm infants have immature metabolism)
How to calculate infant dose using maternal plasma concentration (Cmat), the M:P ratio and volume of milk (Vmilk) ingested
Dose infant = M:P x Cmat x Vmilk
(average value of 0.151/kg/day for milk intake)
What dose is safe for infants in terms of short-term exposure and long-term exposure
Short term exposure
- Relative infant dose should be <10 % of maternal weight corrected dose
- Where drug has pediatric use –> this can be compared to the absolute infant dose
- Observation of infant very important
Long term exposure
- Effects on cognitive development + not well researched except for a couple of selected drugs
What are some ways to reduce drug exposure
- Use lowest app dose
- Discontinue feeding
- Withhold feeding temporarily
- Consider alternative routes of administration
What are some questions to ask patients who are intending to take medicines
- Breastfeeding status? - ALWAYS ask if pregnant or breastfeeding (do not assume)
- Age of baby
- Full term or premature
- Wellness of baby
- Indication - new or previous
- Duration of treatment
- Other medications
- What is the risk of not taking drug
- Any other drugs tied in the past
- Accessed any other information source?
What are some references and resources mothers could use for medicines
- AMH
- APF
- eMIMs
- TOXNET- LactNEd
- Royal womens hospital - medicines, drugs and breastfeeding
- Manufacturers information
- Tom Hale- Medications and Mother’s Milk
