To:  Rosemarie
RE:  Losartan

Losartan is a new product available in the US as Cozaar(Tradename) and as
Hyzaar when it is mixed with hydrochlorthiazide(a diuretic).

It is a new class of product that specifically inhibits the Angiotensin II
receptor site, thus reducing blood pressure.  Rather than inhibiting the
enzymes that make angiotensin such as the ACE inhibitor family,  this drug
directly interacts and blocks the receptor site,  thus reducing blood pressure
directly.

We have no data on its transfer to breastmilk at this time that I can find.
Systemic bioavailability is only 33%, and the elimination half-life of the
active metabolite is 4-9 hours.  Protein binding is approximately 99.8%.
Further, it does not transfer through the blood brain barrier.
It has a rather low volume of distribution and distributes primarily to the
liver and kidney.  I would surmise that due to the above distribution kinetics,
the concentration in milk is going to be exceedingly low but we have no data to
support this contention.  Its use during pregnancy is quite dangerous, (Preg.
Class C) and should never be used in pregnant women.

This product is primarily indicated to replace the ACE inhibitor family in
"only those individuals in which the ACE products are ineffective".  If this is
not the case,  then perhaps the mother could use a typical ACE inhibitor for
which we have proper data,  such as  Captopril,  which is hardly transferred
into milk at all, and has been used safely in breastfeeding women.

I concur with my esteemed colleague, Dr. Newman,  that many physicians jump on
the newest product on the market,  which may or may not be appropriate in this
case.  If an ACE inhibitor is appropriate for this patient,  I would
respectfully suggest captopril as a suitable alternative.

Regards

Tom Hale, Ph.D.
Associate Professor of Pediatrics