Adefovir is a medicine used to treat hepatitis B. When taken long-term, it prevents hepatitis B viruses from multiplying.
What is adefovir?
Adefovir is a medicine used to treat hepatitis B. When taken long-term, it stops hepatitis B viruses from multiplying. Adefovir, also known as adefovirum, belongs to the class of drugs called antivirals. These are drugs that inhibit the reproduction of viruses. Adefovirum was approved in the European Union in 2003. It is prescribed to adults for the treatment of chronic hepatitis B. The drug is usually not used until the patient has been diagnosed with the disease. In most cases, the drug is only used when a liver disease is also present. This can be a disorder of the serum levels or liver inflammation. The drug is marketed in Germany under the name Hepsera. The half-life of the active substance is seven hours, after which it is broken down by the kidneys. In the blood, adefovir is only slightly bound by proteins.
Pharmacologic action
In medical circles, adefovir is classified as a prodrug. This is an initially inactive agent that exerts its effects only after ingestion. After ingestion, adefovir is converted to adenosine monophosphate in a transition state. The phosphate forms a related structure, but it is better absorbed by infected cells. There it is eventually converted to adefovir diphosphate and assumes its active form. Inside the cell, the adefovir diphosphate collides with the naturally occurring substrate deoxyadenosine triphosphate. Since the two compounds are very similar, there is an obstruction of nucleic acid synthesis. As a consequence, the affected cell is prevented from dividing. Overall, the multiplication rate of the viruses is reduced. Colloquially, this procedure is also referred to as suicide inhibition. Since this method can also be used to stop human DNA polymerase, only low concentrations of the active substance may be taken. Furthermore, a continuous increase in resistance can be observed during treatment. This occurs due to a mutation of a polymerase gene. In the long term, the clinically observed resistance can minimize the success of treatment. Therefore, a reduction of the viral load is only possible in the short term. However, this is usually sufficient to prevent further liver damage.
Medical application and use
Adefovir is a prescription drug. It is used exclusively to treat chronic hepatitis B disease. The drug Hepsera, which is represented in Germany, contains the active ingredient in the form of tablets. These are taken orally according to the doctor’s instructions. A bioavailability of around 60 percent can be expected. This means that the active ingredient makes up 60 percent of the total amount. However, the drug is associated with low protein binding. Thus, less than four percent of the ingested amount is available to the circulation. Adefovir is excreted again after a few hours. This occurs via the kidney through filtration and secretion. A half-life of seven hours can be expected. Accordingly, half of the absorbed amount of active ingredient leaves the body after every seven hours. However, it should be noted that the drug is prescribed only in combination with a pending or ongoing liver disease. In addition, active viral replication must be demonstrated. This means that the progression of hepatitis B disease should be checked during initial or follow-up treatment. Depending on the disease history, possible exceptions apply.
Risks and side effects
Adefovir is associated with a number of side effects during treatment. Among the most important side effects is nephrotoxin. It is colloquially referred to as kidney toxin. The naming is due to the toxic effect of the drug, especially against kidney cells. Therefore, kidney function must be checked at regular intervals. If impairment is detected, the physician may make an adjustment to the recommended dose. In addition, gastrointestinal complaints may occur. These are disorders of the digestive system. In case of long-term use, headaches and neck pain may occur. These subside after the end of treatment. Furthermore, adefovir is unsuitable for underage and pregnant patients.Under certain circumstances, a risk-benefit analysis can be carried out. Often, the consequences of the therapy outweigh the associated treatment success. It is still unknown whether the drug appears in breast milk. As a precaution, breastfeeding should be discouraged throughout the treatment period.
