Valaciclovir is one of the most commonly used agents to combat herpes simplex virus infection and shingles. The drug is incorporated into numerous preparations, is a prodrug, and is considered a virostatic agent.
What is valaciclovir?
Valaciclovir is a prodrug of aciclovir used in the therapy of herpes infections and shingles. The term prodrug is used to describe substances that – like valaciclovir – do not themselves produce any immediate effects or success, but only begin to act within the body. Valaciclovir, for example, is converted in the human body into the active ingredient aciclovir, which then kills herpes viruses. The prodrug property provides Valaciclovir with numerous advantages. For example, a bad taste is avoided, solubility is increased, and the bioavailability of the active ingredient is enhanced. In addition, valaciclovir is absorbed more quickly compared to similar substances that do not function as prodrugs. In chemistry, the active ingredient is described by the molecular formula C 13 – H 20 – N 6 – O 4 . Valaciclovir thus has a moral mass of 324.34 g/mol.
Pharmacologic effects on body and organs
From a pharmacological point of view, valaciclovir is not only a virostatic agent but also a prodrug. The active ingredient is rapidly absorbed in the human intestine, so bioavailability is significantly improved compared with similar drugs. Literature reports an availability of approximately 55%, which is more than five times higher than the average value of 10%. After absorption by the body, valaciclovir is converted to the active form, aciclovir. This occurs through metabolism (metabolization). Aciclovir is closely related to the nucleic base guanine, which is a component of DNA and RNA. This enables the substance to penetrate the metabolism of cells and switch them off. This is done by making it impossible for the virus to spread its DNA. The special feature of aciclovir is that it only acts where it is actually needed. This is because the active ingredient only attacks cells that are already infected by the virus. Based on its mechanism of action, valaciclovir is considered a virostatic agent that has antiviral properties against various herpes viruses (including simplex and zoster).
Medical use and use for treatment and prevention.
Compared with other antivirals used to combat herpes, valaciclovir has a wide range of applications. This is because the substance is effective against almost all herpes viruses. The most common types against which valaciclovir is used include cold sores (in the technical world: herpes simplex), shingles and chickenpox (varicella zoster virus), glandular fever caused by the Epstein-Barr virus, and cytomegalovirus. Genital herpes can also be treated with valaciclovir. The dosage required in each case depends on the underlying disease and the individual patient, so that the doctor’s instructions for use must always be observed. As a rule, however, a dose of 1000 mg three times a day is appropriate for a healthy adult. The appropriate dose for children and adolescents under 12 years of age is lower. Valaciclovir is most commonly administered in tablet form. These are taken orally by the patient with sufficient water. The best-known preparations containing valaciclovir include Valtrex in Germany, Austria and Switzerland, and Valaciclomed and Valdacir, which are sold only in Austria. In addition, numerous generics exist.
Risks and side effects
Undesirable side effects may occur after taking valaciclovir. However, this is not necessarily the case. The most common side effects include headache, nausea, dizziness, and a general feeling of being unwell. Occasionally, symptoms of the gastrointestinal tract may also occur after taking valaciclovir. These become noticeable as abdominal pain, diarrhea, vomiting or mild cramps. In addition, a state of confusion or skin reactions such as itching, rash or redness may occur. In addition, the occurrence of photosensitivity is possible. Very rarely, kidney failure or dysfunction of the same occurs. Valaciclovir should not be taken if hypersensitivity or allergy is known.In addition, attention must be paid to interactions. Valaciclovir is actively secreted in the kidney via so-called organic anion transporters (OAT), which is why interdependencies with other organic anions such as probenecid are conceivable. Special caution is also required in combination with substances that are toxic to the kidney. The physician should always be kept informed of all preparations taken to minimize the risk of interactions.
