Topic Overview
Most cold sores heal on their own without prescription medicines. But some antiviral medicines (such as acyclovir or famciclovir) when taken orally (tablets) may
be helpful in reducing the frequency and severity of attacks of
cold sores.
Doctors may prescribe oral antiviral medicines that
can be taken daily to prevent future outbreaks of cold sores. These medicines
may also be given during periods of increased risk of getting cold sores
(such as during cosmetic surgery or sun exposure).
Oral antivirals work best in treating recurring cold sores
if they are taken within 24 to 48 hours of an outbreak of cold
sores.
Pregnant or nursing women should seek their doctors' advice prior to
taking antiviral medicines. Those with kidney problems may be advised to take
lower doses.
Some examples of oral antiviral medicines prescribed to treat cold
sores include the following:
Acyclovir
Acyclovir (Zovirax) tablets may slightly shorten the duration of pain and the healing time of a first attack of cold sores.footnote 1
Common side effects of acyclovir tablets include nausea, diarrhea, and headache.
A lower dose of oral acyclovir is needed for people who have
reduced kidney function.
Famciclovir
Famciclovir (Famvir) is sometimes used to treat the herpes virus that causes
cold sores and genital herpes (as well as the virus that causes shingles). This medicine is available only by
prescription and is taken orally in tablet form.
If you are pregnant or nursing, you should talk with your doctor
before taking famciclovir.
This medicine is not recommended for people who have had an
allergic reaction to it in the past.
Possible mild side effects include itching, fever, headache,
fatigue, nausea, or diarrhea.
Valacyclovir
Valacyclovir (Valtrex) capsules are available by prescription only. It is absorbed by the body much better than
some other antiviral medicines (such as acyclovir).
Possible side effects include skin rash,
allergic reaction, headache, dizziness,
insomnia, and
fatigue.
Children, pregnant women, and people who have HIV or who have had
bone marrow or kidney transplants should talk with their doctors before taking
this medicine.