Valtrex, known generically as valacyclovir, is an antiviral medication used to treat cold sores, chicken pox, shingles and genital herpes. It is also used for recurrent genital herpes outbreaks. Valtrex does not cure the disease, but it prevents the virus from multiplying, according to eMedTV. Genital herpes may still be spread while taking Valtrex, so it's important to practice safe sex using a latex condom. Side effects may be associated with the use of Valtrex.
Respiratory and Allergic Effects
Valtrex is taken by mouth, one to several times a day. It is possible to experience a severe allergic reaction, called anaphylaxis, when taking Valtrex. Shortness of breath, called dyspnea, can occur during an allergic reaction, as well as severe itching, hives and swelling of the face, mouth and throat. This is an emergency situation requiring immediate medical attention. Drugs.com states that other respiratory side effects include upper respiratory tract infection and nasopharyngitis, an infection of the nasal passages and pharynx that occurs most often in children.
Headache, Nausea and Vomiting
Headache is one of the most common side effects reported with the use of Valtrex. According to The Merck Manual, up to 38 percent of those taking Valtrex experience headache. Other common side effects are nausea and vomiting; taking Valtrex with a meal decreases chances of upset stomach. Valtrex should be taken for the duration of the prescription. The dosage should not be increased without a physician's consent. Any side effects that are severe or do not lessen over time should be reported to the prescribing physician.
Depression and Aggressive Behavior
Valtrex may cause central nervous system side effects, such as depression or aggressive behavior. According to RxList, other central nervous system side effects include confusion; decreased consciousness; tremors and uncoordinated movements, called ataxia; agitation; seizures; and hallucinations.
Metabolic Side Effects
Valtrex may cause some metabolic side effects, such as high blood pressure and hypoglycemia, or low blood sugar, according to Drugs.com. More serious metabolic side effects have also been reported. Kidney and liver problems can arise while taking Valtrex. Taken in higher doses, this drug can precipitate out in the renal tubules, causing kidney failure, so it should be taken with a full glass of water. Liver toxicity has occurred in patients, causing yellowing of the skin and eyes. Thrombotic thrombocytopenic purpura/hemolytic uremic syndrome, or TTP-HUS, is a life-threatening clotting disorder. This condition causes clotting in tiny blood vessels of some organs, leading to organ failure and possibly death. Neutropenia, or low white blood cell count, may occur, leaving some more prone to developing infection. The development of any of these serious side effects requires immediate medical attention.
