Viread (tenofovir)

November 2006     View PDF     En español
Reprinted from www.aidsmeds.com, US

What is Viread?
Viread is an anti-HIV medication. It is in a category of HIV medicines called nucleotide reverse transcriptase inhibitors. Viread prevents HIV from altering the genetic material of healthy T-cells. This prevents the cells from producing new virus and decreases the amount of virus in the body.

Nucleotide analogues, such as Viread, are very similar to nucleoside analogues (e.g., Retrovir® (AZT), Zerit® (d4T), and Epivir® (3TC)). The only difference is that nucleotide analogues, unlike nucleoside analogues, are chemically preactivated and thus require less processing in the body for them to become active.

Viread, manufactured by Gilead Sciences, was approved by the U.S. Food and Drug Administration for the treatment of HIV in 2001.

Viread is available in pharmacies as a single drug, which is always combined with other anti-HIV drugs, or in the combination capsules Truvada® (Viread and Emtriva®) and Atripla™ (Viread, Emtriva, and Sustiva® [efavirenz]).

Viread is also active against the hepatitis B virus (HBV), the virus responsible for hepatitis B. Although it has not been approved by the FDA for the treatment of hepatitis B, some doctors prescribe it to treat both hepatitis B and HIV. See What is known about side effects? below for more important information regarding Viread and hepatitis B.

Top of page

What is already known about Viread?
The dose is one 300mg pill, taken once a day. Truvada®, which contains Viread and Emtriva®, needs to be taken once a day.

Viread can be taken either with or without food.

Viread is not approved for children younger than 18 years of age.

Studies have demonstrated that Viread is effective for the treatment of HIV when combined with other anti-HIV drugs, usually at least one other nucleoside reverse transcriptase inhibitor (NRTI) and either a protease inhibitor or non-nucleoside reverse transcriptase inhibitor (NNRTI). Viread should not be taken alone (as monotherapy) or with just one other anti-HIV drug.

For HIV-positive adults beginning anti-HIV drug therapy for the first time, Viread is listed as a "preferred" NRTI option – used in combination with Sustiva® (efavirenz) and either Epivir® (3TC) or Emtriva® (emtricitabine) – by the United States Department of Health and Human Services in its treatment guidelines. Alternative ways to use Viread, in a first-time drug regimen, are also listed.

Viread is active against many strains of HIV resistant to Retrovir® (AZT), Zerit® (d4T), Videx®/Videx EC® (ddI), Hivid® (ddC), and Ziagen® (abacavir). There is also some data from studies indicating that HIV that has become resistant to Epivir® (3TC) may be even more sensitive to Viread. The drug is also active against virus containing the Q151M mutation – a single mutation that results in high-level resistance to multiple nucleoside analogues.

Viread may be less active against strains of HIV that contain the K65R mutation in its reverse transcriptase gene. To figure out if your virus has this mutation, your doctor can order a genotypic drug-resistance test.

Top of page

What about drug interactions?
HIV-positive people must be very careful about using Viread in combination with Videx®/Videx EC® (ddI). There are two important warnings to know about:

The twice-daily Viracept dosing schedule involves taking two 625mg tablets every 12 hours. An alternative option is to take five 250mg tablets every 12 hours. The twice-daily dosing schedule, using the 625mg tablets, is preferred by many healthcare providers, as it involves taking the fewest number of pills the fewest number of times a day.

Drug regimens consisting of Sustiva® (efavirenz) or Viramune® (nevirapine) plus Viread and Videx/Videx EC have been associated with premature drug failure. If you are receiving Viread and Videx EC with either Sustiva or Viramune, you may want to discuss alternative options with your doctor.

Viread increases the amount of Videx/Videx EC in the body. This can increase the risk of Videx-related side effects. In turn, if Viread and Videx/Videx EC are used together, Videx EC should be taken at a dose of 250mg once a day (reduced from the usual daily dose of 400mg a day).

Because there are now a number of concerns regarding the use of Viread in combination with Videx/Videx EC, many experts recommend avoiding this combination altogether. HIV-positive people should be careful if they use Viread in combination with Reyataz® (atazanavir), a protease inhibitor used to treat HIV. Viread can decrease Reyataz levels in the bloodstream and Reyataz can increase Viread levels in the bloodstream. Thus, if you are using Reyataz in combination with Viread, your doctor should also prescribe low doses of Norvir® (ritonavir), another protease inhibitor that can significant boost the amount of Reyataz in the bloodstream. The correct dose is 300mg Reyataz plus 100mg Norvir, combined with the standard daily dose of Viread. To make sure that the increased Viread levels do not cause kidney damage (a possible side effect of Viread), blood tests to monitor kidney function should be performed regularly.

Levels of lopinavir, one of the two protease inhibitors in Kaletra® (lopinavir/ritonavir), can decrease when the drug is combined with Viread. Kaletra can also increase Viread levels in the bloodstream. If Kaletra and Viread are used together, it is important to watch out for potential side effects of Viread (e.g., kidney problems).

Top of page

What about side effects?
Lactic acidosis, which can be fatal, and severe liver problems have been reported in people taking nucleoside reverse transcriptase inhibitors (NRTIs). Contact your doctor immediately if you experience nausea, vomiting, or unusual or unexpected stomach discomfort; weakness and tiredness; shortness of breath; weakness in the arms and legs; yellowing of the skin or eyes; or pain in the upper stomach area.

Viread may cause bone problems. In one clinical trial conducted by the manufacturer involving HIV-positive patients who were new to anti-HIV therapy, Viread [combined with Sustiva® and Epivir®] was more likely to cause decreased bone mineral density (osteopenia) – which can lead to osteoporosis – than Zerit® (d4T) [combined with Sustiva and Epivir]. This can increase the risk of bone breakage, including the hip, spine, and wrist. Researchers are currently looking into the seriousness of this possible side effect. If you have a history of bone fracture or are at risk for osteopenia, your doctor may want to consider ordering bone scans on a regular basis while you are taking Viread. While it's not clear if calcium and vitamin D supplementation can help reverse this side effect, it might be a good idea if you have either osteopenia or osteoporosis and are taking Viread.

Viread can be problematic for HIV-positive people who have a history of kidney problems (renal impairment). If you have a history of kidney problems, your doctor will need to order a simple laboratory test to measure your "creatinine clearance" – the rate your kidneys remove this protein produced by muscles from the bloodstream. Depending on the results of this test, your Viread dose may need to be decreased. It is always important to be careful if using Viread in combination with Vistide® (cidofovir), Cytovene® (ganciclovir), and Valcyte™ (valganciclovir), three treatments for CMV that can also cause kidney problems.

Anti-HIV drug regimens containing NRTIs, including Viread, can cause increased fat levels (cholesterol and triglycerides) in the blood, abnormal body-shape changes (lipodystrophy; including increased fat around the abdomen, breasts, and back of the neck, as well as decreased fat in the face, arms, and legs), and diabetes. These side effects of anti-HIV drug therapy are reviewed in our lessons on Lipodystrophy, Facial Lipoatrophy, and Risks To Your Heart (Hyperlipidemia).

Nausea, vomiting, diarrhea, and flatulence (intestinal gas) are the most likely short-term side effects of Viread.

If you have hepatitis B and HIV and plan to stop taking Viread, your doctor might want to frequently check your liver enzymes after stopping treatment. This is because Viread is also active against the hepatitis B virus (HBV). If Viread is stopped abruptly, it can cause liver disease to "flare" and damage the liver.

Top of page

Can pregnant women take Viread?
Viread is classified by the FDA as a pregnancy category B drug. Pregnancy category B means that animal studies have failed to demonstrate a risk to the fetus, but there are no adequate and well-controlled studies in pregnant women. HIV-positive women who become pregnant should discuss the benefits and possible side effects of anti-HIV treatment to help protect their babies from HIV.

It is not known whether Viread passes into breast milk and what effect they may have on a nursing baby. To prevent transmission of the virus to uninfected babies, it is recommended that HIV-positive mothers not breast-feed.

Top of page

What should I tell my doctor before taking Viread?
Before taking this medication, tell your doctor if you have: kidney disease; liver disease (including hepatitis B); or bone problems.

Tell your doctors and pharmacists about all medicines you take. This includes prescription medications, over-the-counter products, or herbal/natural remedies.

Top of page

Where can I learn more about clinical trials of Viread?
If you would like to find out if you are eligible for any clinical trials that include Viread, there is an interactive website run by ACRIA, the AIDS Community Research Initiative of America.

Another useful service for finding clinical trials is AIDSinfo.nih.gov, a site run by the U.S. National Institutes of Health. They have “health information specialists” you can talk to at their toll-free number at 1-800-HIV-0440 (1-800-448-0440).

Top of page