During clinical trials of Valtrex, sexual side effects were not reported. However, it is difficult to say with complete assurance that a particular complaint is not due to a medication, even though the complaint is not a reported side effect. If you are taking Valtrex and sexual side effects occur, your healthcare provider may adjust your dosage of Valtrex or prescribe another medication for your condition.
An Overview of Valtrex Sexual Side Effects
Valtrex® (valacyclovir hydrochloride) is an antiviral medication that is used to treat certain infections caused by the herpes virus (shingles, cold sores, chickenpox, and genital herpes). As with all medicines, Valtrex has possible side effects. However, sexual side effects have not been reported, either before or after clinical studies were conducted. If a person does develop sexual side effects, such as impotence or a decrease in libido, it is difficult to know whether these problems are caused by another condition or by Valtrex itself.
Understanding Clinical Trials
Before medicines are approved, they must go through several clinical studies, where thousands of people are given a particular medicine and are then compared to a group of people not given the medicine. In these studies, side effects are always documented. As a result, it is possible to see what side effects occur, how often they appear, and how they compare to the group not taking the medicine. Side effects are then usually separated into those that occur in more than 1 percent of people and those that occur in less than 1 percent of people. Sexual side effects, such as a decrease in sex drive (libido) or impotence, were not reported as either a common or rare side effect with Valtrex during these studies.
Yet, clinical trials are designed to factor out as many variables as possible in order to understand whether the medicine works and its possible side effects. This means that once approved, it is possible that new side effects may occur, since a wider range of people are now taking the medicine and for longer periods of time. However, once a medicine is approved, a drug does not usually continue to be studied, so certain side effects that only occur rarely may never be documented, especially if they are not a serious side effect. Thus, it is difficult to say with complete assurance that a particular complaint is not due to a medication, even though the complaint is not a reported side effect.
Written by/reviewed by: Kristi Monson, PharmD;Arthur Schoenstadt, MD
Last reviewed by: KristiMonson, PharmD;
List of references (click here):
Valtrex [package insert]. Research Triangle Park, NC: GlaxoSmithKline;2010 March.
Food and Drug Administration, Center for Drug Evaluation and Research. Electronic orange book: approved drug products with therapeutic equivalence evaluations. FDA Web site. Available at: http://www.fda.gov/cder/ob/. Accessed December 4, 2009.
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