Ganciclovir is the name given to a virostatic agent. It is effective against herpes viruses.
What is ganciclovir?
Ganciclovir is an analog of the nucleic base guanine. As a virostatic agent, it is used to treat infections caused by herpes viruses. The active ingredient was approved in Europe in the 1980s. In Germany, the drug is used under the preparation names Virgan and Cymeven. There is a structural relationship between the antivirals ganciclovir, penciclovir, and aciclovir.
Pharmacologic Action
As a virostatic agent, ganciclovir has the property of inhibiting the growth of viruses. The drug exerts its effects primarily against herpes viruses, which include the complete human herpes virus family. Its effects are particularly pronounced against the cytomegalovirus (CMV). For this reason, medicine usually uses it against this germ. After the ganciclovir enters the patient’s body, a chemical transformation occurs there. The active form of the antiviral is formed, which is ganciclovir triphosphate. This substance is formed mainly in the body cells infected by viruses. The drug is phosphorylated by different kinases, which serves the subsequent incorporation into the DNA of viruses. Ganciclovir shows great similarity to the viral DNA building block guanine. This misincorporation results in a chain break, as ganciclovir is not recognized as a viral polymerase building block. Further replication of the viral DNA therefore does not occur. The virus can therefore no longer replicate. One of the disadvantages of ganciclovir, however, is that its effect is not targeted. Thus, the antiviral not only inhibits the growth of the viruses, but also has a negative effect on the metabolic processes of healthy body cells. As a result, there are sometimes some serious side effects. The oral bioavailability of ganciclovir is low, at only 5 percent. For this reason, it is often administered intravenously. The antiviral is excreted from the body almost unchanged by the kidneys. If renal function is normal, the elimination half-life is between 1.5 and 3 hours.
Medical use and application
The indications for use of ganciclovir primarily include diseases caused by human herpesvirus 5 (HHV 5). It is also known as cytomegalovirus. Generally, the indications are immunodeficiency (such as AIDS) and organ transplants. As an eye gel, ganciclovir is also suitable for the treatment of ocular herpes (keratitis herpetica). Furthermore, experimental treatments of malignant degenerations, for which oncolytic viruses are responsible, take place. For negative selection, ganciclovir is also used in biochemistry. Due to the low oral bioavailability of the antiviral, the patient is usually administered two single doses daily, amounting to 5 milligrams per kilogram of body weight. This is administered as an infusion at time intervals of 12 hours. The infusion is administered via a large vein. However, ganciclovir can also be administered orally. In this case, the patient takes 1 gram per day between meals. External dosage forms in the form of eye gel have also been available in Germany since 2006.
Risks and side effects
Because ganciclovir has considerably higher toxic properties than other antivirals such as aciclovir, there is a greater risk of side effects, which can be very diverse. For example, there is often a reduction in certain white blood cells, diarrhea, difficulty breathing, a lack of white blood cells, loss of appetite, fungal infections in the mouth, headaches, sleep problems, urinary tract infections, cellulitis, anxiety disorders, depression, confusion, abdominal pain, nausea, vomiting, coughing, difficulty swallowing, and constipation. Other undesirable side effects include impaired thinking, anorexia, inflammation of the skin, itching, night sweats, ear pain, nerve disorders, liver function disorders, muscle pain, back pain, fever, fatigue, rigidity, chest pain, weakness, and weight loss. Even detachment of the retina and blood poisoning (sepsis) are possible.Occasionally, cardiac arrhythmias, loss of hearing, visual disturbances, severe allergic reactions, heartburn, hair loss, male infertility, and renal failure and psychosis also occur. If the patient suffers from an allergy or hypersensitivity to ganciclovir or other antivirals such as valaciclovir, valganciclovir and aciclovir, the drug must not be administered under any circumstances. This also applies if there is a pronounced deficiency of platelets or white blood cells or if the hemoglobin level is too low. Cautious dosing by the physician is required in the case of renal dysfunction. In such cases, the physician must weigh the risks against the benefits. Ganciclovir must not be used under any circumstances during pregnancy and breastfeeding, as the child could otherwise be seriously damaged or suffer malformations. Consistent contraception is recommended when taking the drug. Ganciclovir is also not suitable for children under 18 years of age. Taking ganciclovir at the same time as certain other medicines may result in interactions. For example, there is often a risk of increased disturbance of blood cell formation. The risk is particularly high with active ingredients used to treat cancer. These include cytostatics such as vinblastine and vincristine and chemotherapeutic agents such as pentamidine and dapsone. There is also a risk with antifungal agents such as flucytosine and amphotericin B. It is not recommended to administer ganciclovir with the active ingredient zidovudine, which is also used to fight viruses. In the case of a combination, the patient risks most severe damage to blood cell formation. If ganciclovir is given concomitantly with cephalosporins or penicillins, there is a risk of seizures.
