Tylenol RID

[Lov2shop]

Hello, I’m trying to understand the RID for Tylenol. I know it is listed as 6.41%-8.82%, but does that mean that much goes to baby? If that were the case, a 500mg of Tylenol would mean baby would get 30-40 mg of Tylenol? An infant dose of Tylenol is 40mg…so 30-40mg seems quite high?

After reading the studies provided on Infant Risk, it states on one that a baby would receive an average of .92mg after mother took 1000mg. So .92 is quite a lot smaller than 30mg, and sounds much more reasonable considering. Can anyone help explain this?

I did call but the nurse was not able to answer.

Also, as long as it’s a low dose (typically 500mg-1000mg a day) or under)- is it ok for baby if mom is taking Tylenol on a regular daily basis for chronic pain? NSAIDS cannot be used due to an allergy.

[kaytlin]

Hello! RID's are commonly misunderstood...and it is a pet peeve of mine! Thank you for asking.

It is the percent of the relative infant dose. If you took mom's dose and shrunk it down to a baby-sized dose, that would be the complete relative infant dose (100% RID). Then, we estimate how much of that dose a fully breastfed baby would get via milk. This is a much smaller value than a straight percentage of the mother's dose.

So, if an average mom is 70 kg, 500mg/70kg = 7.1 mg/kg (this is actually lower than a typical 10 mg/kg acetaminophen infant dose). If the RID is 8%, an infant would get 0.57 mg/kg (7.1*8/100). If you have a 10 kg infant, the infant would get 5.7 mg via milk (fully breastfed) per day. If it is long term, I recommend discussing the exposure with the pediatrician to individualize risk; for a healthy infant, this dose is likely fine.

Hope this helps,
Dr. Krutsch

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