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Possible food and drug interactions when taking this medication
If you are taking Valtrex with certain other drugs, the effect of either drug could be increased, decreased, or altered. Check with your doctor before combining Valtrex with cimetidine (Tagamet) and/o
r probenecid (Benemid).
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Overdosage
When taken by people with kidney disorders, excessive doses of Valtrex have been known to cause psychological problems and kidney failure. If you suspect an overdose, check with your doctor immediatel
y.
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Cautions
High doses of Valtrex have proved dangerous in people whose immune system is compromised because of HIV infection, bone marrow transplant, or kidney transplant.
If your kidneys are not funct
ioning properly, or you are taking drugs that may damage the kidneys such as Neomycin or Streptomycin, Valtrex can make your condition worse or affect your central nervous system (brain and spinal cor
d).
Effects on the central nervous system are more common in older adults, leading to such symptoms as agitation, confusion, and hallucinations. Their kidneys are also more likely to be affe
cted; and those with kidney problems need a smaller dose. Older adults tend to suffer the pain of shingles for a longer time after healing has begun.
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Precautions Before Using This Medicine
ChildrenˇXStudies on this medicine have been done only in adult patients. There is no specific information comparing use of Valtrex in children with use in other age groups.
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How should you take this medication?
If you are taking Valtrex for shingles, you should start using it as soon as possible after your doctor has made a diagnosis. It's best to see a doctor and start the drug within 48 hours of first noti
cing the rash. If you wait more than 72 hours after you first get a herpes zoster rash, the medication may not be effective.
If you are using Valtrex for genital herpes, begin taking it at t
he first sign of an attack. The medication may not be effective if you wait longer than 72 hours after the first attack or 24 hours after a later attack.
If you are taking Valtrex for cold s
ores, you should start using it at the earliest signs of infection, such as tingling, itching, or burning.
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What side effects may occur?
Check with your doctor as soon as possible if the following side effect occurs:
- Painful menstruation, including abdominal cramps, diarrhea, or nausea
- Black, tarry stools; ches
t pain; chills; cough; decreased frequency/output of urine; fever; flu-like symptoms; headache; lower back/side pain; reduced mental alertness; shortness of breath; unusual tiredness; yello
w eyes or skin
- Back, leg or stomach pains; changes in behavior, especially in interactions with other people; difficulty breathing or swallowing; fast, pounding, or irregular heartbeat
; high blood pressure; itching; lightheadedness when getting up from a lying or sitting position; redness of skin ;
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