Ganciclovir

As Ganciclovir is called a virostat. It works against herpes viruses.

What is ganciclovir?

Ganciclovir is an analogue of the nucleobase guanine. As an antiviral, it is used to treat infections caused by herpes viruses. The drug was approved in Europe in the 1980s.

In Germany, the drug is used under the product names Virgan® and Cymeven®. There is a structural relationship between the antivirals ganciclovir, penciclovir and acyclovir.

Pharmacological effect

As a virostatic agent, ganciclovir has the property of inhibiting the growth of viruses. The drug develops its effect primarily against herpes viruses, which include the entire human herpes virus family. Its effects against the cytomegalovirus (CMV) are particularly pronounced. For this reason, medicine usually uses it against this germ.

After the ganciclovir enters the patient's body, there is a chemical change there. The result is the effective form of the virostat, which is ganciclovir triphosphate. This substance is mainly formed in the body cells that are infected by viruses. The drug is phosphorylated by different kinases, which is used for the subsequent incorporation into the DNA of the viruses.

Ganciclovir is very similar to the viral DNA building block guanine. This incorrect incorporation results in a chain break, since ganciclovir as a viral polymerase is not recognized as a building block. There is therefore no further replication of the virus DNA. The virus can no longer multiply.

However, one of the disadvantages of ganciclovir is that its effects are not targeted. The antiviral not only inhibits the growth of viruses, but also has a negative effect on the metabolic processes of healthy body cells. The consequence of this can be some serious side effects.

The oral bioavailability of ganciclovir is low and is only 5 percent. For this reason, it is often given intravenously. The antivirals are excreted from the body almost unchanged via the kidneys. If kidney function is normal, the elimination half-life is between 1.5 and 3 hours.

Medical application & use

The areas of application for ganciclovir primarily include diseases caused by human herpes virus 5 (HHV 5). It is also known as the cytomegalovirus. As a rule, the indications are an immune deficiency (such as AIDS) and organ transplants.

As an eye gel, ganciclovir is also suitable for treating ocular herpes (keratitis herpetic). In addition, there are experimental treatments of malignant degenerations for which oncolytic viruses are responsible. Ganciclovir is also used in biochemistry for negative selection.

Due to the low oral bioavailability of the virostat, the patient is usually given two single doses a day, which are 5 milligrams per kilo of body weight. The administration takes place as an infusion at time intervals of 12 hours. The infusion is given through a large vein.

However, ganciclovir can also be administered orally. In this case, the patient takes 1 gram per day between meals. Since 2006, external dosage forms in the form of eye gel have also been on offer in Germany.

Risks & side effects

Since ganciclovir has significantly higher toxic properties than other antivirals such as acyclovir, there is a greater risk of side effects, which can be very diverse. There is often a reduction in certain white blood cells, diarrhea, breathing difficulties, 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, stomach pain, nausea, vomiting, coughing , Difficulty swallowing and constipation.

Other undesirable side effects are thought disorders, anorexia, inflammation of the skin, itching, sweats at night, ear pain, nerve disorders, liver disorders, muscle pain, back pain, fever, fatigue, rigidity, chest pain, weakness and weight loss.

Detachment of the retina and blood poisoning (sepsis) are possible. Occasional cardiac arrhythmias, loss of hearing, visual disturbances, severe allergic reactions, heartburn, hair loss, male infertility, kidney failure and psychosis also occur.

If the patient suffers from an allergy or hypersensitivity to ganciclovir or other antivirals such as valaciclovir, valganciclovir and acyclovir, the drug must not be administered to him under any circumstances. This also applies if there is a pronounced deficiency in platelets or white blood cells or if the hemoglobin level is too low.

A careful dosage by the doctor is necessary in case of kidney dysfunction. In such cases, the medical professional has to weigh the risks and benefits against each other.

Under no circumstances should ganciclovir be used during pregnancy and breastfeeding, as this could cause serious harm or malformations to the child. When taking the product, consistent contraception is recommended. Ganciclovir is also not suitable for children under the age of 18.

Concomitant use of ganciclovir with certain other medicinal products can cause interactions. Often there is a risk of increased disruption of blood cell formation. The risk is particularly high with agents used to treat cancer. These include cytostatics such as vinblastine and vincristine, as well as chemotherapy drugs such as pentamidine and dapsone. There is also a risk of anti-fungal agents such as flucytosine and amphotericin B.

It is not recommended to give ganciclovir with the active ingredient zidovudine, which is also used to fight viruses. In the case of a combination, the patient is at risk of severe damage to blood cell formation. If ganciclovir is given at the same time as cephalosporins or penicillins, there is a risk of seizures.