Valacyclovir Hydrochloride Extended-Release Tablets treats infectious diseases caused by herpes simplex virus types I and II and varicella zoster, such as herpes of the lips and mouth and genital tract. The drug has an antiviral effect by inhibiting the synthesis of viral DNA. Adverse reactions such as dizziness, thirst, headache, insomnia, nausea, abdominal pain, diarrhea, vomiting, proteinuria, arthralgia, loss of appetite, itching of the skin, decrease in white blood cells, menstrual disorders, and mild elevation of urea nitrogen may be observed with the use of the drug. When the drug is combined with zidovudine, it can cause deep fatigue and lethargy, etc.; when combined with probenecid, it can reduce the excretion of the drug itself. It is contraindicated for those who are allergic to the drug or acyclovir. Use with caution in hepatic and renal insufficiency; use with caution in dehydration; use with caution in lactating women. When used in elderly patients, the drug dose should be adjusted. The drug can pass through the placenta, so the use of pregnant women must be carefully considered. If you need to use the drug, please strictly follow the doctor’s instructions under the guidance of the medication, do not self-medication.