Teaching in Twenty
Medications and Breast Milk
Barbara L. Philipp, MD, FAAP, FABM
Professor of Pediatrics
Boston University School of Medicine
Boston Medical Center
Objectives: HANDOUT M2
• Name 7 contraindications to breastfeeding
• Describe 3 pharmacokinetic factors that
influence medications passing from mom to
baby via breast milk
• List 2 reliable resources for information
about medications and breast milk
Background - Mothers
• 90% of women are prescribed a
medication in first week postpartum
• Mothers worry about effect of medication
on nursing infant
• Leads to: non compliance, weaning,
avoidance of breastfeeding
• 50% of mothers more reluctant to take a
medication while nursing than during
pregnancy
Background – Clinicians
• Frequently
err
erroneously
on
the side of
caution
• Slide credit:
M Bartick
Background – Clinicians
• And…
• Baby may not comply with “temporary”
weaning
• Weaning, even temporarily, is traumatic
• Need to balance short term med concerns
with long term breastfeeding benefits
Seven contraindications to
breastfeeding (AAP 2005)
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Mother HIV + (in USA)
Use of illegal drugs by mother
Certain medications
Active, untreated TB in mother
Galactosemia in baby
Mother HTLV +
Herpes on breast
A mother is taking the following medication or drug.
She asks you, “Is it to breastfeed?”
What is your advice? HANDOUT M1
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Cocaine
Methadone
Glass of wine
Heparin
Phenytoin (Dilantin)
Lithium
Magnesium sulfate
TMP-SMZ (Bactrim)
Tetracycline
How to decide if a medication
or drug is ok?
• Pharmacokinetic factors
• Factors which govern drug transfer across
membranes into breast milk as well as the
metabolism of the drug in mother and
infant
Pharmacokinetic factors
1.
2.
3.
4.
5.
6.
Passive diffusion
Molecular weight
Protein binding
Lipid solubility
Half life
Oral bioavailability
Passive diffusion
• Drugs move in and out
of breast milk
• High to low
• With time direction
may shift
• Example: alcohol
Molecular weight
• High molecular weight limits movement
into breast milk
• MW >500 daltons does not enter breast
milk
Molecular weight: examples
• Insulin: MW > 6,000 daltons
• Heparin: MW 40,000 daltons
• Ethanol: MW 200
Protein binding
• Medications circulate in maternal
circulation bound or unbound to albumin
• Only unbound drug gets into maternal milk
• Definition of good protein binding = > 90%
Protein binding
High protein binding
• Propranolol 90% L2
• Diazepam 99% L3
Low protein binding
• Lithium 0% L3
Lipid solubility
• Drugs that are very lipid soluble penetrate
into breast milk in higher concentration
• Drugs that are active in the CNS are drugs
with high lipid solubility
Half life
Short half life drugs
• Alcohol 24 min
• Keflex 50 min
• Ibuprofen 120 min
• General anesthesia
Long half life drugs
• Prozac 216 hours
Oral bioavailability
• Amount of drug that is absorbed from the
gut into the blood stream
Oral bioavailability
Drug
Maternal GI Tract
Maternal Plasma
Breast Milk
Infant GI Tract
Infant Plasma
Oral bioavailability
• Low bioavailability may be due to
– Reduced absorption in GI tract
– Poor GI stability due to acidity
– High first-pass uptake by liver
Poor oral bioavailability
• Gentamycin
– <1% oral bioavailability
• Insulin (destroyed in gut)
– 0% oral bioavailability
• Heparin (destroyed in gut)
Summary
Drugs transfer into human milk if they:
• Attain high conc in maternal plasma
• Are small enough
• Are non-protein bound
• Are highly lipid soluble
Then once in breast milk:
• Are affected by oral bioavailability in
baby’s gut
In general, baby gets
<1% of maternal dose of
drug
Resources
• BAD
• Very Very Very Bad
• Physician’s Desk
Reference (PDR)
• Major concern is
legal risk
Resources
• OK
• AAP Statement
• Committee on Drugs.
The transfer of drugs
and other chemicals in
human milk. Pediatrics
2001;108(3):776-789
Resources
THE BEST
• Medications and
Mothers’ Milk
• Thomas Hale, Ph.D.
• www.ibreastfeeding.com
Medications and Mothers’ Milk
Lactation Risk Category
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L1 Safest
L2 Safer
L3 Moderately safe
L4 Possibly hazardous
L5 Contraindicated
Resources
THE BEST
• LactMed.com
What’s your advice?
• Cocaine
• No: Hale L5, drug of abuse
contraindicated by AAP
• Methadone
• Yes: Hale L3, (if HIV neg, no illegal drugs)
• Alcohol (glass of wine)
• Yes: Hale L3, but common sense,
moderation, peak levels
What’s your advice?
• Heparin
• Yes: Hale L1
– MW 30,000 daltons, oral bio 0%
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Phenytoin (Dilantin)
Yes: Hale L2, AAP ok
Lithium
Used to be No: Hale L5
Now Yes: Hale L3 with close observation
What’s your advice?
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•
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Magnesium sulfate
Yes: Hale L1
TMP-SMZ (Bactrim)
Yes: Hale L3, AAP ok
Tetracycline
Yes: Hale L2, AAP ok – binds to
calcium in the milk (<3 weeks use)
Take Home Points
• Don’t guess
• Use Medication and Mothers’ Milk
(www.iBreastfeeding.com)
• Use LactMed (or toxnet)
References
• Hale, Thomas. Medications and Mothers’
Milk, 14th ed. Amarillo, TX: Pharmasoft,
2010
– www.ibreastfeeding.com
• LactMed on ToxNet
– Massbfc.org has link to AAP document and
LactMed