Spironolactone in Mother's Milk & Infant Safety

[Dr. T]

Dear Dr. Hale & colleagues,
I am trying to find current information on the safety of maternal Spironolactone in a nursing 5 month old healthy infant. Dr. Hale's book, Medication & Mother's Milk, refers to an article from 1970 by Drs. Phelps and Karim. Their data is based on one or two women. I am wondering if there is more current information based on a larger data base available to determine safety? The mother's Endocrinologist is inclined NOT to permit mom to take the med while she nurses because of the doctor does not permit it during pregnancy. Mom has taken Spironolactone successfully in the past to control acne.
I have contacted both Dr. Phelps and Dr. Aziz Karim. They have no additional information since their 1970 article.
I believe Dr. Hale's book rates Spironolactone as L2, probably safe, but I feel there should be a larger "N" than 1 or 2 women from the 70's.
Is more known?
Thank you for your time and consideration.
Dr. T/Atlanta, GA.

[kathsems]

Hi Dr. T,

Wondering if you ever found more information on the safety of using Spironolactone while nursing. I am 31 with PCOS and also use Spironolcatone to control various PCOS symptoms. I am going to start weaning soon, and expect my PCOS symptoms to increase again once I start the weaning process. Any information from anyone would be greatly appreciated. Thank you!

[admin-james]

Hi, kathsems and Dr. T, thanks for your post.

I apologize for not getting back to you in a timely manner about this issue. The short answer is that there has not been any new information published since the 1970s concerning spironolactone in breastmilk. The original study provided enough data to calculate that the babies were receiving between 2-4% of the mother's medication in the breastmilk. This figure is called the Relative Infant Dose (RID). Pharmacology experts generally regard drugs with an RID of <10% to be "safe" for use with breastfeeding because the amounts involved are so small. In this case, spironolactone is prescribed directly to new babies at doses around 1-3 mg/kg/day without significant side effects. While Dr. T is correct that small sample sizes are usually a weak basis for a clinical recommendation, it seems very unlikely that larger trials would re-evaluate the RID to be >10%.

Pfizer's prescribing information advises against taking spironolactone while breastfeeding, but this is typical for all drugs and all manufacturers. They cite a single study in rats showing an increase in tumors as evidence. No followup study has demonstrated this effect in humans. After reviewing this topic, we have decided to maintain our L2 rating for this drug. The scale goes from L1 (Safest) to L5 (Hazardous).

Please call us at the InfantRisk Center if this has not completely answered your question. (806)352-2519

-James Abbey, MD
and
-Thomas W. Hale, Ph.D.