Chronic use of Valtrex

[Ainara]

I know Valtrex is safe to use while nursing, but what about using long term?

I've had 5 shingles outbreaks the last two I was pregnant and my OB put me on Valtrex since 30 weeks until 6 weeks post partum, as soon as I stopped taking it I got shingles again, now the doctor tells me I need to take the medicine until I either find a doctor willing to treat me while nursing (VERY hard in WI) or I wean the baby. I'm currently taking it for the acute infection (3,000 mg/day) but the dosage after that will be 1,000mg/day. Is it safe to take this medicine for long periods of time (months) while nursing an infant (he is almost 7 weeks old)

[admin]

Ainara:

Valtrex is just a pro-drug that is rapidly metabolized to acyclovir. Below are data on the transfer of acyclovir to milk, which is low. Only about 1.5% of the dose of acyclovir reaches milk, and less than 30% of this is absorbed orally in the infant.

I'd suggest the risk of long-term exposure is probably low. But have you discussed the Shingles Vaccine with anyone? While you cannot take it while pregnant, it might not be a bad option for you while breastfeeding, and it might block some of this frequent reinfections. I'd suggest a discussion with an Infectious Disease expert to see if it is a suitable option for you.

I can't really advise you that long-term exposure of the infant is safe, but the low levels in milk probably would make the risk very low.

Tom Hale Ph.d.





Acyclovir levels in breastmilk are reported to be 0.6 to 4.1 times the maternal plasma levels.[1] Maximum ingested dose was calculated to be 1500 ?g/day assuming 750 mL milk intake. This level produced no overt side effects in one infant. In a study by Meyer[2], a patient receiving 200 mg five times daily produced breast milk concentrations averaging 1.06 mg/L. Using this data, an infant would ingest less than 1 mg acyclovir daily. In another study, doses of 800 mg five times daily produced milk levels that ranged from 4.16 to 5.81 mg/L (total estimated infant ingestion per day = 0.73 mg/kg/day).[3] Topical therapy on lesions other than nipple is probably safe. But mothers with lesions on or close to the nipple should not breastfeed on that side. 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 0.87 mg/kg/day.