The
National Reye's Syndrome Foundation (NRSF), the U.S. Surgeon General, the Food
and Drug Administration (FDA) and the Centers for Disease Control and
Prevention recommend that aspirin and/or aspirin containing products not be
given to anyone under the age of 19 years during a fever-causing illness.(1-3)
If a female is nursing or breastfeeding a child, the NRSF and the World Health
Organization (WHO) Working Group on Human Lactation considers aspirin intake by
nursing mothers to be unsafe.(1,4) They base their recommendations on the
fact that a nursing baby can receive about 4-8% of the mother's dose and that
continuous exposure of small doses can cause of a buildup of aspirin in the
body of the infant.(1,4,5)
Other
professional groups, such as the American Academy of Pediatrics Committee on
Drugs (AAP) list aspirin and 5-aminosalicylic acid as, "drugs that have
been associated with significant effects on some nursing infants and should be
given to nursing mothers with caution".(6) This recommendation is
based on the 5-ASA causing diarrhea and aspirin being reported to cause
metabolic acidosis.Other
referenced texts also indicate that aspirin should not be used by a mother
whose nursing infant has an active viral illness due to a small chance that the
child may develop Reye's syndrome.(7) While there is conflicting data as to
the amount of aspirin exposure to a nursing infant with individual patient
cases, one study evaluating 8 nursing women who took 1 gram of aspirin found
the average salicylate milk concentrations to be 2.4 mg/mL at 3 hours and the
average salicyluric acid milk concentrations to be 10.2 mg/L at 9 hours.(8-10)
The authors suggested these levels translated into a relative infant dose of
9.4% of the maternal dose.10 Due to the available data, aspirin was given
a lactation risk category of L3, which is designated as "moderately
safe".(7)
The
characteristics of a medication that facilitate its ability to enter into the
breast milk include:
- Ability to attain high plasma concentrations in
the breastfeeding mother
- Having a low molecular weight defined as being
approximately less than 500
- Having a low degree of protein binding
- Ability to pass into the brain easily or have a higher degree of lipophilicity.(7)
Aspirin is known to meet a couple of these characteristics that are likely
contributing to some of its presence in breast milk with its molecular weight
being 179 g/mol and being highly lipid soluble.(11) The relative infant
dose will not only factor in these characteristics but will also be influenced
by the dose the mother ingested, timing of the administration in relation to
breastfeeding, and the frequency of administration while nursing.
Despite
the above recommendations from regulatory agencies, professional organizations
and other reference resources, we are unaware of any documented cases of Reye's
syndrome in a nursing infant receiving breast milk from a mother who also took
aspirin. Regardless, due to the severity of Reye's syndrome, the presence
of aspirin in the breast milk, and the availability of other analgesic options
besides aspirin, it would be prudent to avoid the use of all aspirin or aspirin
derivatives while breastfeeding an infant who is also experiencing a viral
infection.
