What is Viread?
Viread is a medicine containing the active substance tenofovir disoproxil. It is available in blue almond-shaped tablets (245 mg).
What is Viread used for?
Viread is used to treat adult patients infected with the following viruses:
- human immunodeficiency virus type 1 (HIV-1), a virus that causes acquired immune deficiency syndrome (AIDS). Viread should be taken in combination with other antiviral medicines. In the case of patients who have already taken other medicines to treat HIV infection, doctors should prescribe Viread only after a careful examination of the patient's previous antiviral treatments and after evaluating the possibility that the virus responds to antiviral therapies;
- hepatitis B virus, a virus that can cause hepatitis B (a liver disease). Viread is used in patients with chronic hepatitis B who have compensated liver disease (when the liver is damaged but works normally), symptoms that the virus is multiplying and symptoms of liver damage in the blood and liver tissue samples.
The medicine can only be obtained with a prescription.
How is Viread used?
Treatment with Viread should be started by a doctor who has experience in the treatment of HIV infection or chronic hepatitis B. The recommended dose of Viread is one tablet once a day, taken with food. In exceptional cases, patients who have particular difficulty in swallowing can dissolve the tablet in at least 100 ml of water, orange juice or grape juice and drink the resulting suspension (liquid). Viread should be used in patients with kidney problems only if it is considered that the potential benefits of the treatment outweigh the risks. Dose frequency may need to be reduced in patients with moderate to severe kidney problems.
If Viread therapy is discontinued, patients infected with hepatitis B virus, with or without HIV, should be monitored closely for exacerbations of hepatitis (inflammation of the liver).
How does Viread work?
The active ingredient in Viread, tenofovir disoproxil, is a "prodrug" that is converted into tenofovir in the body. Tenofovir is a nucleotide reverse transcriptase inhibitor (NRTI).
In HIV infection it blocks the activity of reverse transcriptase, the enzyme produced by the HIV virus that allows it to infect cells and reproduce. Viread, taken in combination with other antiviral medicines, reduces the amount of HIV in the blood and keeps it at a low level. Viread does not cure HIV infection or AIDS, but it may delay the damage to the immune system and the development of infections and diseases associated with AIDS.
Tenofovir also interferes with the action of an enzyme produced by the hepatitis B virus called "DNA polymerase", which participates in the formation of viral DNA. Viread blocks the production of DNA by the virus, preventing it from multiplying and spreading.
What studies have been carried out on Viread?
For HIV treatment, Viread has been studied in 3 main studies involving 1 343 HIV-infected adults. The first two studies compared the effects of adding Viread to existing treatment compared to adding placebo (a dummy treatment) in 741 patients who had been on treatment for HIV infection for at least four years, with no signs of improvement. Viread has also been evaluated in a study conducted on 602 treatment-naïve patients (never previously treated for HIV treatment), comparing Viread with stavudine (another antiviral drug), in combination with lamivudine and efavirenz (other drugs antiviral).
The main efficacy indicator of all three studies was the levels of HIV in the blood.
For the treatment of hepatitis B, the effectiveness of Viread has been compared to that of adefovir dipivoxil (another antiviral drug) in two studies. The first study involved 382 patients with HBeAg negative hepatitis (infected with a virus that underwent a mutation [edit] to a more difficult form of hepatitis B to treat), while the second involved 272 patients with HBeAg positive hepatitis (infected with a common type of hepatitis B virus). Both studies looked at the number of patients who had responded completely to the treatment after 48 weeks, ie with a virus level in the blood of less than 400 copies / ml and with a reduction in liver damage observed by a biopsy (when a tissue sample hepatic is taken and observed under a microscope).
What benefit has Viread shown during the studies?
In HIV-infected patients, Viread in combination with other antiviral drugs showed a reduction in viral load. In the two studies carried out on patients with previous treatment experience, the subjects in whom Viread was added to the ongoing therapy showed a reduction in viral load of about 75% after four weeks and after 24 weeks, compared to a slight increase or a slight decrease in viral load of approximately 5% observed in patients treated with placebo. In naïve patients, Viread was as effective as stavudine, with similar percentages of patients in the two groups in which a viral load of less than 400 copies / ml was detected after 48 weeks.
In patients with hepatitis B, Viread was more effective than adefovir dipivoxil. After 48 weeks, 71% of patients with HBeAg negative hepatitis and 67% of patients with HBeAg positive hepatitis treated with Viread had a complete response compared to 49% and 12% of patients treated with adefovir dipivoxil.
What is the risk associated with Viread?
The most common side effects (seen in more than 1 patient in 10) with Viread are nausea, vomiting, diarrhea, dizziness and hypophosphataemia (low levels of phosphate in the blood). For the full list of all side effects reported with Viread, see the Package Leaflet.
Viread should not be used in people who may be hypersensitive (allergic) to tenofovir, tenofovir disoproxil fumarate or any of the other substances.
Like all other NRTIs, Viread can also cause lactic acidosis (accumulation of lactic acid in the body) and, in the children of mothers treated with Viread in pregnancy, mitochondrial dysfunction (injuries to the energy-producing cellular constituents that can cause blood problems) . As with other anti-HIV drugs, patients receiving Viread to treat HIV infection may be at risk of lipodystrophy (changes in body fat distribution), osteonecrosis (death of bone tissue) or immune reactivation syndrome (symptoms of infection caused by reactivation of the immune system).
Why has Viread been approved?
The Committee for Medicinal Products for Human Use (CHMP) decided that Viread's benefits are greater than its risks in combination with other antiretroviral medicines for the treatment of HIV-1 infected patients over the age of 18 and for the treatment of HIV. chronic hepatitis B in adult patients with compensated liver disease, with evidence of active viral replication, persistently elevated serum alanine aminotransferase (ALT) levels and histological evidence of active inflammation and / or fibrosis. The committee recommended that Viread be given marketing authorization.
Viread was originally authorized under "exceptional circumstances" because only limited information was available for scientific reasons at the time the initial authorization was granted for the treatment of HIV-1 patients. Since the company provided the additional information requested, the condition referring to "exceptional circumstances" was removed on 8 July 2005.
What measures are being taken to ensure the safe use of Viread?
The company that makes Viread will develop a letter and educational programs for doctors to inform them about the effects of the medicine on the kidneys, as well as to remind them when and how to use the product in patients with kidney problems.
Other information about Viread:
On 5 February 2002, the European Commission granted Viread a marketing authorization valid throughout the European Union to Gilead Sciences International Limited. The marketing authorization was renewed on 5 February 2007.
The full EPAR for Viread can be found here.
Last update of this summary: 05-2008.
