POSITIVELY AWARE MARCH/APRIL 2011
brand name: Viread
common name: tenofovir disoproxil fumarate (DF)
class: Nucleotide analog reverse transcriptase inhibitor
(nucleotide analog, NtRTI, or nuke)
manufacturer: Gilead Sciences, Inc. | www.viread.com, (800) GILEAD5 (445–3235)
Standard dose: One 300 mg tablet once a day, with or without food, with no dietary restrictions. Dosing frequency needs to be adjusted for people with decreased kidney function. Take missed dose as soon as possible, unless it is almost time for your next dose. Do not double up on your next dose.
AWP: $832.49 / month
Potential side effects and toxicity
Overall, fairly well tolerated; however, diarrhea, nausea, vomiting, and gas are the most common side effects of Viread. Decreases in bone mineral density (BMD) have been observed with the use of Viread in HIV-positive people. BMD monitoring should be considered in people who have a history of pathologic bone fracture or are at risk for osteopenia or osteoporosis. Creatinine clearance (CrCl) should be assessed before initiating treatment with Viread. CrCl and serum phosphorus should be monitored in patients at risk. Less common side effects of Viread, occurring with undetermined incidence, include kidney toxicities and low blood phosphate. Rare but potentially serious toxicity with all NRTIs: enlarged, fatty liver (hepatomegaly with steatosis) and lactic acidosis (accumulation of lactate in the blood and abnormal acid-base balance). Lactic acidosis may cause persistent fatigue, abdominal pain or distension, nausea/vomiting, difficulty breathing or shortness of breath, and enlarged liver. The effect of Viread on children and individuals with severe liver impairment was not studied during drug development. However, since Viread is not metabolized by the liver (and appears to have less toxicity in the liver than the majority of the NRTIs), it is believed the impact on individuals with liver disease should be minimal.
Potential drug interactions
Do not take with Truvada or Atripla, since Viread is in these medications. Videx levels are increased with Viread; therefore, use with caution and monitor closely when taking Viread, Truvada, or Atripla with Videx or Videx EC to avoid Videx-related toxicity, including neuropathy. See More Information. Viread decreases the concentration levels of Reyataz. In addition, both Reyataz and Kaletra increase Viread concentrations. Higher Viread concentrations could increase the risk of Viread-associated adverse events, including kidney disorders. Patients taking Reyataz and Viread should be monitored for Viread-associated adverse events. When taken with Viread, it is recommended that Reyataz 300 mg is given with Norvir 100 mg (all as a single daily dose with food). Unboosted Reyataz (without Norvir) should not be taken with Viread. No dosage adjustment is needed when used with Kaletra. You should not take Viread with Hepsera, a hepatitis B treatment.
More information
Viread combined with Emtriva (also available as Truvada) is considered the preferred NRTI combination by U.S. HIV treatment guidelines. Viread is also combined with Emtriva and Sustiva (NNRTI) to make up Atripla, the first single-tablet HIV regimen. The body clears most of Viread through the kidneys and dosing adjustment is recommended for those with impaired kidney function. Serious kidney problems have been rare and most have been in those with pre-existing kidney disease or taking kidney-toxic drugs. However, the characteristics of kidney toxicity are still being defined. The manufacturer recommends that individuals with impaired kidney function be monitored closely, especially people with advanced HIV disease, even in those who did not start out with kidney disease. There have been reports of individuals who experienced severe kidney disorder, including some taking Kaletra with Viread. Since Kaletra increases blood levels of Viread, it may increase the likelihood of Viread side effects. Like Epivir and Emtriva, Viread has activity against hepatitis B, which may flare up when Viread is discontinued. Patients co-infected with HIV/HBV should use Epivir or Emtriva with Viread as their NRTI backbone to increase activity and avoid HBV resistance. These patients should be closely monitored by their physician. Viread may have prolonged activity against hepatitis B even when resistant to Epivir. Viread was approved last year for use in adolescents ages 12 to 18 who weigh more than 77 pounds, making it easier for Viread and Truvada to be used in HIV prevention studies with this population. The FDA noted, “Although the effect of supplementation with calcium and vitamin D was not studied, such supplementation may be beneficial for all patients [taking Viread].” See package insert for more complete information on potential side effects and interactions.
Doctor’s comments
Because of its safety and effectiveness, the combination of tenofovir and FTC, in the form of Truvada, or, when combined with efavirenz as Atripla, has become the preferred nucleoside combination in both the DHHS and IAS-USA guidelines. In most cases, an initial antiretroviral regimen should include tenofovir unless there’s a good reason to use something else. Tenofovir’s main flaw is kidney toxicity: it can reduce kidney function, and can also cause wasting of phosphate in the urine, leading to bone problems. However, these are toxicities that can be detected using simple and standard lab tests, and they’re uncommon, especially in people taking tenofovir with efavirenz as part of an initial regimen. Kidney toxicity may be somewhat more common when tenofovir is combined with protease inhibitors, but these are still widely used, recommended regimens. The other concern is bone: It’s now clear that there’s a mild and transient loss of bone density whenever you start antiretroviral therapy, but the loss of bone may be somewhat more pronounced in people taking tenofovir. —Joel Gallant, MD, MPH
Activist’s comments
Its convenient once-daily dosing and relatively few side effects have made Viread the preferred backbone of most regimens. Since this is a drug that people can be on for decades, both patients and their doctors should be vigilant about possible loss of bone mineral density (osteopenia/osteoporosis) and kidney problems and other meds that can worsen those problems. And like Epivir and Emtriva, Viread has activity against hepatitis B, so those with hep B should check with their doctors when constructing a regimen with this drug to avoid the possibility of developing resistance to HBV drugs. —Jeff Taylor
