Potential side effects and toxicity: Overall, fairly well tolerated, however, individuals may experience the following: nausea, headache, diarrhea, rash, vomiting, asthenia, flatulence, abdominal distension/pain and anorexia. See AZT page for rare but potentially fatal toxicity with all NRTIs as a drug class (they have not been seen with Viread).

Potential drug interactions: The levels of Videx EC and Videx (ddI) are increased by 44–60% when given at the same time as Viread. Therefore, a dose reduction to 250 mg for Videx is recommended. See tips. Viread decreases the concentration levels of Reyataz. In addition, Reyataz (and Kaletra) increases Viread concentrations. The reasons for these interactions are not fully understood. Higher Viread concentrations could increase the risk of Viread-associated adverse events, including renal disorders. The FDA suggests that patients receiving 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 and Viread 300 mg (all as a single daily dose with food). Reyataz without Norvir should not be taken with Viread.

Tips: Remember, Truvada is two drugs in one pill, so see the pages for those drugs, Emtriva and Viread. The race is on: Epzicom, or Truvada? Both are a combination of two drugs taken as one pill, once a day. (This is called FDC, for “fixed-dose combination.”) Both were approved by the FDA on the same day last August. All four drugs have already been out in the drug store. Moreover, two of the four drugs (Epivir and Emtriva) are virtually identical (except that Emtriva lasts longer in the blood; however, in head-to-head data, Emtriva did not do as well as Epivir 150 mg twice a day). Perhaps the quick and dirty way to divide the two is by toxicity: the drugs in Truvada are fairly tolerable, however, more and more patients are complaining of abdominal distension due to excessive gas production and bloating. The Ziagen in Epzicom unfortunately has a hypersensitivity reaction (HSR) in anywhere from 5–8% of people taking it.

On the other hand, while kidney toxicity with the Viread in Truvada appears to be rare, the toxicity profile is still being worked out with this newer drug, and so are its drug interactions. (See Viread for some of the problems that have arisen.) Which brings up another difference—Epivir and Ziagen have been extensively studied, Emtriva and Viread have not. As a result, surprises continued to pop up with Viread after it hit the drug store.

Then there’s resistance. Viread has a primary resistance mutation (K65R on a resistance test), but it’s rare and Viread tends to continue to work for people even when they develop the mutation. K65R is also the primary mutation for Ziagen, so again, you probably can’t go from Epzicom to Truvada and expect to see huge improvement if your virus has come back while on Epzicom.
And what about Truvada’s longer lasting blood levels? Some doctors think that makes it a better choice, other doctors think otherwise, as that has yet to be determined. Many medical providers will say that the effect of half-life and of many of the resistance mutations—including K65R—have not been clinically proven. In other words, what does it do for your health? Experienced doctors, however, will avoid prescribing either FDC for people with the mutations at codon 103 on their resistance test.