[Question #3431] Valtrex affect on PCR results

37 months ago
Over the past several months, I've had a series of mouth ulcers that my doctor thought, but wasn't sure, was HSV related. I finally was able to see the doctor on the second day of an outbreak when the sore was yet to be broken down into an ulcer. She did a PCR swab, which came back negative for HSV. However, the day prior to this, I had begun to take Valtrex. By the time I saw the doctor, I had taken two, 2g doses of Valtrex, 12 hours apart. I'm wondering if that would have caused a false negative on the PCR test. What do you think?
Terri Warren, RN, Nurse Practitioner
Terri Warren, RN, Nurse Practitioner
37 months ago
I am so sorry this question slipped past me! 
It is possible that the Valtrex influenced the swab test yes.  But it is more likely that ulcers inside the mouth are not herpes.  Normally they are canker sores and those are not caused by herpes - we don't know exactly why people have them but often it is a reaction to some foods. 
Can you tell me more about the mouth ulcers?  Where in the mouth? How long they last?  are they related to anything specific?

Terri
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