Tuesday, May 10, 2011

Pharmacology and Breastfeeding

Medications, drugs, herbs--all can affect breastfeeding and some are contraindicative to breastfeeding.  The good news is, very few demand cessation of breastfeeding and information about drugs is readily available on a number of reputable websites.

I want to offer some general guidelines since those sitting for the exam will not be able to "Google" medications during the course of answering the multiple choice questions.

As a general rule, many medications are compatible with breastfeeding, but selecting the "safest" medications is advisable.  The aveolar epithelium of the breast is a lipid barrier that is most permeable in the first few days of lactation (when colostrum is produced). The transfer of water-soluble drugs and ions is inhibited by the hydorphobic barrier.  Water-soluble materials pass through pores in the basement membrane and para cellular spaces.  Drugs that have low lipid solubility and are non ionized will diminish its excretion into milk.
Medications should also be avoided the first 5-7 weeks postpartum, if possible.  During the early postpartum period the free fraction of some drugs increases and more readily crosses into the milk.(Lawrence & Lawrence, Breastfeeding a Guide for the Medical Profession, 6th Edition)
Some basic considerations for drug interaction with breastmilk includes:

  • Route of administration
The route of administration (your baby is always exposed through the GI tract, but drugs can enter your system several different ways: orally, intravenously, intramuscularly, topically, or through inhalation - topical medications (skin creams) and medications inhaled or applied to the eyes or nose reach the milk in lesser amounts and more slowly than other routes and are almost always safe for nursing mothers; oral medications take longer to get into the milk than IV and IM routes (the drug must first go through the mother's GI tract before it enters the bloodstream, and the milk supply)-with IV drugs, the medications bypasses the barriers in the GI tract to enter the milk quickly and at higher levels, and with IM injections, drugs transfer quickly into the milk because the muscles have so many blood vessels, so the drug enters the bloodstream quickly. http://www.breastfeedingbasics.com/html/drugs_and_bf.shtml
  • Absorption rate
  • Half-life (choose medications with short half-lives and take immediately after nursing)
  • Molecular weight (choose medications with high molecular weights)
  • Maternal plasma level (higher maternal plasma levels result in higher milk levels)
  • Ionization (choose medications that are ion trapped)
  • Dosage (higher dosage has a greater chance transferring into the milk)
  • pKa (choose drugs with a lower pKa)
  • Solubility (high liquid solubility penetrate the milk in higher concentrations)
  • Protein binding (desire high protein binding)

A good reference including reputable links is http://www.aap.org/breastfeeding/files/pdf/Lactmed.pdf
Medications listed as safe (categorized by lactation risk L1-L5) http://www.kellymom.com/health/meds/aap-approved-meds.html
For a list of medications contraindicative to breastfeeding visit http://www.breastfeeding-magazine.com/Unsafe-Drugs-and-Medications.html

Galactagogues, lactagogues and herbs must also must be closely monitored and dosage must be carefully calculated.  Just because they are not classified as drugs and FDA approved does not mean they are safe.  Many moms will try to self-medicate and they must be warned of the danger of the over-use of such herbs.

Birth control with progesterone only is a better option for mothers desiring to use a pill.  Barrier methods are compatible with breastfeeding and the LAM method is also effective if used correctly.

I highly recommend having a copy of Dr. Thomas Hale's Mother's Milk and Medications in your personal library.  Reading the preface of the newest edition will shed a lot of light on medications and how they interact and pass into the baby's blood stream.  Never give advice or perscribe any medication, this blog is for information only and should be used to form some basic understanding of drugs and how they are categorized.

When a mom contacts me about a medication, I initially look it up, see if there is a safer alternative and then suggest she ask her doctor if the other medication would be a plausible alternative to treat her condition and if it would be compatible with breastfeeding.  I also photocopy or print the information about the drug or direct her to the appropriate website.  I never recommend any medication or advise a mom not to take a medication that has been prescribed, that is outside of my scope as an IBCLC

This blog is for informational purposes only.  For medical advice, consult a medical professional.

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