Active Ingredients

Tenofovir – Effect, Application & Risks

Tenofovir

Tenofovir (also tenofovir disoproxil ) is used therapeutically for HIV-1 and hepatitis B infections. Tenofovir disoproxil is activated to tenofovir in human cells . On the one hand, it inhibits the reverse transcriptase in HI viruses (or the DNA polymerase in hepatitis B viruses ) and, on the other hand, it is built into the virus DNA as the wrong building block, so that the virus can no longer multiply. It is generally well tolerated, but can lead to kidney failure in pre-existing kidney damage .

What is tenofovir?

Tenofovir is an antiviral drug ( virostatic ) and belongs to the group of nucleoside inhibitors of reverse transcriptase (NRTI) in HI viruses. The active ingredient can also block the DNA polymerase in hepatitis B viruses.

It is a modified adenosine monophosphate analogue and consists of a pentose, a nucleobase and a phosphoric acid residue. Tenofovir disoproxil is the prodrug that is activated by endogenous enzymes to form tenofovir.

Pharmacological action

The drug is taken in tablet form and should be taken with meals. The correct dosage must be discussed with the doctor treating you and must be strictly adhered to, otherwise resistance may develop. There is low plasma protein binding and the plasma half-life is 12 to 18 hours. Excretion mainly takes place via the kidneys .

The active ingredient tenofovir disoproxil is taken up unchanged by the human cell and phosphorylated into nucleotide triphosphates and activated by special enzymes called kinases. Tenofovir has a dual mechanism of action. On the one hand, the activated derivatives inhibit the viral reverse transcriptase in the HI virus and the DNA polymerase in hepatitis B. On the other hand, they are also incorporated into the viral DNA as the wrong building block. Consequently, DNA synthesis is now terminated due to the missing 3`hydroxyl group on the activated tenofovir. This prevents the virus from multiplying further.

However, DNA polymerases also exist in the human body, particularly in the mitochondria . These can also be inhibited by the drug, with corresponding side effects.

Medical Application & Use

Tenofovir is used in the treatment of HIV-1 and hepatitis B infection. The drug was initially approved for HIV therapy in Europe in 2002 and has been indicated for the treatment of chronic hepatitis B since 2008. Tenofovir is used in particular in patients with hepatitis B and active virus replication and elevated liver enzymes.

In the treatment of HIV, tenofovir is always used in combination with other drugs. The therapy can be used in adults and adolescents aged 12 to 18 years.

In pregnant women with chronic hepatitis B infection, tenofovir can reduce transmission of the virus to the unborn child. Under study conditions, the drug was given in the last trimester of pregnancy and continued until 4 weeks after birth . A significant increase in malformations in the unborn could not be observed until then.

It should be noted that treatment with tenofovir does not cure HIV-1 or hepatitis B, so the patient can still transmit viruses to other people even while on therapy. Appropriate protective measures are therefore essential to avoid infection.

Risks & side effects

In general, tenofovir is very well tolerated. Common side effects are nausea , diarrhea , tiredness , dizziness and headaches . However, caution is advised in patients with existing renal impairment. The drug has a nephrotoxic effect and in rare cases can lead to kidney failure. Tenofovir should also not be taken with other medications that can also damage the kidneys. Tenofovir is contraindicated in patients requiring dialysis .

Inhibition of human mitochondrial DNA polymerase can result in some rare but important long-term side effects. Infants in particular who have been exposed to nucleoside therapy in utero may be at increased risk of side effects. Lactic acidosis can result from excess lactic acid in the blood . This manifests itself in deep and rapid breathing , drowsiness , as well as nausea, vomiting and stomach pain . This should get immediate medical attention as this side effect can be fatal.

Inflammation of the pancreas ( pancreatitis ) can also occur, which is particularly noticeable through pain in the upper abdomen. In rare cases, muscle and joint weakness, damage to the nerve tracts ( polyneuropathy ) and lipodystrophy (body fat redistribution disorder) can occur. It should not be taken if you have a known allergic reaction to tenofovir itself or to other components of the drug.

Pregnancy is a particular challenge and requires an individual, medication-based approach. Breastfeeding is not permitted during therapy, as it is not yet known whether the drug passes into breast milk .

Lisa Newlon
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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.