Tenvir (Tenofovir Disoproxil)

TDF and CHB

The World Health Organization (WHO) estimates that around 254 million people were living with chronic hepatitis B (CHB) in 2022. Chronic HBV infection can lead to long-term complications such as cirrhosis, liver failure and a higher risk of hepatocellular carcinoma (HCC). Over the last decade, HBV management has improved, and effective antiviral treatment options include tenofovir disoproxil fumarate (TDF).

TDF is an oral prodrug of tenofovir, a nucleotide reverse transcriptase inhibitor that works against both hepatitis B virus (HBV) and HIV-1. For HIV-1, TDF is used only in combination with other antiretroviral medicines. For chronic hepatitis B, TDF is used as an antiviral treatment option; in the UK, patients should be tested for HIV-1 before starting TDF for HBV.

Clinical trial data show that TDF can help suppress HBV DNA in many patients during long-term treatment. In adult trials, ongoing follow-up included treatment for up to 384 weeks in extension phases. In the treatment of chronic hepatitis B, the optimal duration of treatment is unknown.

Important safety note: severe acute worsening of hepatitis B has been reported after stopping anti-hepatitis B treatment, including TDF. In the United Kingdom, liver function should be monitored with clinical and laboratory follow-up for at least several months after stopping treatment; if appropriate, restarting treatment may be considered.

Indications

VIREAD (tenofovir disoproxil fumarate, TDF) is indicated for the treatment of chronic hepatitis B virus (HBV) in adults and children aged 2 years and older who weigh at least 10 kg.

Drug interactions

TDF is mainly eliminated by the kidneys. Taking it with medicines that are eliminated by active tubular secretion may increase concentrations of tenofovir and/or the other medicine; medicines that reduce kidney function may increase tenofovir concentrations. In the treatment of chronic hepatitis B, TDF should not be used in combination with adefovir dipivoxil.

• Coadministration decreases atazanavir concentrations. When used with TDF, atazanavir should be given with ritonavir. Certain HIV-1 protease inhibitors (including lopinavir/ritonavir) and some HCV regimens can increase tenofovir concentrations-monitor for signs of tenofovir toxicity, including kidney-related side effects.
• TDF increases didanosine concentrations. Dose reduction and close monitoring for didanosine toxicity are warranted.
• Examples of medicines eliminated by active tubular secretion include aciclovir, cidofovir, ganciclovir, valaciclovir, valganciclovir, aminoglycosides (for example, gentamicin), and high-dose or multiple NSAIDs. If used together, monitor kidney function as clinically appropriate.

Possible side effects

As well as its intended effects, this medicine may cause side effects. Assessment of side effects in CHB with compensated liver disease is based on controlled clinical trials in 641 people who received treatment during a 48-week double-blind period.

In these trials, the most common side effect (all grades) was nausea (9%). Other treatment-emergent side effects reported in more than 5% of participants included abdominal pain, diarrhoea, headache, dizziness, fatigue, nasopharyngitis, back pain and skin rash.

It is important to note that stopping treatment can lead to a flare-up (worsening) of hepatitis B. During follow-up after stopping treatment, monitor liver function with clinical and laboratory tests for at least several months. If appropriate, restarting treatment may be advisable.

Storage

Store TDF tablets at 25°C (77°F); excursions are permitted to 15-30°C (59-86°F). Keep the bottle tightly closed and dispense only in the original container. Do not use if the seal over the bottle opening is broken or missing. Keep out of the sight and reach of children.