Medication Use in Lactation

Question 1

What is the prevalence of drug use while breastfeeding?

Answer 1

• HCP often provide overly cautious info on breastfeeding during medication use –> “When in doubt, don’t breast feed”
• Even temporary interruptions in breastfeeding can be detrimental
  – decreased milk supply
  – exposure to infant formula

Mothers need accurate info

Question 2

What is the mechanism by which drugs transfer into breast milk?

Answer 2

PASSIVE DIFFUSION
- Transcellular (transverse capillary wall; small un-ionized lipid soluble molecules)

• Intercellular (paracellular) (avoids alveolar cell entirely - large molecules Ig, cow milk protein)
• Ionophore (polar molecules enter via binding to carrier proteins within cell membrane)

ION TRAPPING & pKa
- non-ionized form passes through lipid membrane
- basic drugs w/ higher pKa
– relatively greater amount ionized in milk, thus is “trapped”
- can result in milk / plasma ratio > 1
- opposite effect for acidic drugs

Question 3

What are the factors to consider before deciding to use medication?

Answer 3

Infant Factors:

Age of infant? Premature?
- <6 months at highest risk of drug ADRs

Immature BBB in 1st year of life
- lipophilic drugs w/ CNS SE’s are more likely to transfer into breastmilk & cause CNS SE’s

Health status of the infant?
- Premature? Major organ dysfunction?

Feeding habits? Exclusively breast fed? Formula or solid food?

Was the infant exposed in utero?

Is the drug absorbed by the infant?

Will the drug accumulate in the infant b/c of immature drug metabolic pathways?

Is the drug used therapeutically in peds?

Are potential infant SE easy to monitor?

Maternal Factors:
- Are there non-drug tx’s?
- Duration of tx?
- Can tx be delayed?
- Are there drug options that are safer in lactation?
- Is the drug absorbed? If it’s how does the mom metabolize the drug?
- Timing
- Will the drug affect milk supply?

Question 4

What is the safety of general classes of drugs?

Answer 4

Drugs reported to cause ADRs:
- analgesics, antibiotics, antihistamines, sedatives

Recreational Drugs:
- Alcohol –> milk / plasma ration ~ 1 (delay breastfeeding 2 hours after EACH drink)

• Cigarettes –> avoid M/P ratio = 2.9 (NRT suggested)

Drugs of concern during lactation:
- Amiodarone M/P ratio 5-13

• Certain B-blockers M/P ~5
• Lamotrigine - may reach TI plasma levels, decreased metabolism
• Lithium
• Chemotherapy - cytotoxic agents
• Radiopharmaceuticals - may need to temporarily withhold breastfeeding
• Drugs of abuse - ilicit & rx

Drug that affect lactation:
- DECREASE milk production (dopamine agonist; bromocriptine, cabergoline, pseudoephedrine, estrogen containing BCP)

• INCREASE milk production (dopamine antagonists stimulate prolactin production; metoclopramide, domperidone; fenugreek)