To :    Deb Shinskie, RN


Valacyclovir is the L-valyl ester of acyclovir.  It is a acyclovir pro-drug
converted extensively and almost completely to Acyclovir and L-valine(an
amino acid)

Valacyclovir is converted to acyclovir and L-valine by valacyclovir
hydrolase via first-pass intestinal and hepatic metabolism.   Acyclovir is
detectable in plasma within 15 minutes of oral valacyclovir administration.
The half-life of the parent is short(undetectible by 3 hours).

Although there is no data available concerning breast milk
levels(particularly of valacyclovir),  from the metabolism and distribution
of this product,  it is apparent that once in the plasma,  it would be so
rapidly hydrolysed to acyclovir,  that kinetically,  it can be considered to
be equivalent to acyclovir as far as breastfeeding is concerned.   I have
enclosed below the monograph from my book on acyclovir.=20



Tom Hale, Ph.D.


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ACYCLOVIR  *
Generic  =3D ACYCLOVIR
Category =3D Antiviral, for herpes simplex
Acyclovir levels in breastmilk are reported to be 0.6 to 4.1 times the
maternal plasma levels.  Maximum ingested dose was calculated to be 1500
=B5g/day assuming 750 mL milk intake.  This level produced no overt side
effects in one infant.  In another study,  doses of 800 mg five times daily,
produced milk levels that ranged from 4.16 to 5.81 mg/L(total infant
ingestion per day=3D 0.73 mg/kg/day).   Topical therapy (not nipple) is
probably safe.  If applied to nipples, they should be washed thoroughly
prior to feeding.  Toxicities associated with acyclovir are few, and usually
minor.  Acyclovir therapy in neonatal units is common and produces few
toxicities.  Calculated intake by infant would be less than 1 mg/day.
Breastfeeding  in women positive for herpetic infections is problematic due
to possible transmission of virus to infant.   AAP Compatible with
breastfeeding.

AHL=3D 2.4 hrs.                  M/P=3D 0.6-4.1                    PB=3D=
 9-33%
PHL=3D 3.2 hrs.(neonates)        PK =3D 1.5 - 2 hrs.


*Medications and Mothers' Milk  1995 Ed.
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T.W. Hale, Ph.D.
Associate Professor of Pediatrics
Texas Tech University School of Medicine

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