Brand name: Emtriva

Generic name: emtricitabine, or FTC

Class: Nucleoside reverse transcriptase inhibitor (nucleoside, NRTI, or nuke)

Manufacturer: Gilead Sciences, Inc., www.gilead.com, (800) GILEAD-5 (445-3235)

AWP: $504.37/month for 200 mg capsules; $110.38 for 170 mL solution (10 mg/mL)

Standard Dose: One 200 mg capsule once a day, with or without food, with no dietary restrictions. The dosing needs to be adjusted for children and people who have decreased kidney function. It is also available as an oral solution for children three months and older and adults who are not able to swallow the capsules. Take missed dose as soon as possible, unless it is closer to the time of your next dose. Do not double up on your next dose.

Potential side effects and toxicity: Very tolerable. Side effects (rarely seen) may include headache, diarrhea, nausea, and rash. Flare-up of HBV (hepatitis B) in people co-infected with HBV has occurred when Emtriva was discontinued because it also treats HBV (see "More information"). Skin discoloration (darkening of the skin on the palms and the soles of the feet) can occur, but is generally mild and otherwise harmlesss. See chart for potential drug class side effects.

Potential drug interactions: No significant drug interactions. Do not take Emtriva with Atripla, Combivir, Complera, Epivir, Epivir-HBV, Epzicom, Trizivir, or Truvada, since they contain Emtriva or medication equivalent to Emtriva.

More information: Emtriva is similar to Epivir; both treat HBV and have the same resistance profile for HIV and HBV. However, unlike Epivir, Emtriva remains in blood cells for a longer interval. Emtriva is known to be very effective against chronic hepatitis B (although the manufacturer has not applied for FDA approval for this treatment). If you have HIV and HBV and your hep B needs treatment but your HIV doesn't, you should be treated for both. You should never be treated only for HBV without treatment for HIV. Emtriva and Viread both work against HBV and HIV and can be used together as the NRTI backbone to increase activity and avoid HBV resistance, but there are other HBV treatments available that can be combined with HIV meds. If you are co-infected with HIV and HBV and you stop Emtriva, your HBV may reactivate and you may experience signs and symptoms of acute HBV. You should be closely monitored by your physician. If your HIV develops resistance to Epivir or Emtriva, it does not mean that your HBV is also resistant to them. Emtriva is available as a combination tablet with Viread (tenofovir), which is called Truvada. Truvada is the only NRTI combination on the preferred list of the U.S. HIV treatment guidelines for the NRTI component of first-time therapy. Drug resistance that the virus develops against Emtriva, the M184V mutation, makes the virus less fit to replicate. It also slightly improves the antiviral activity of Retrovir (zidovudine) and Viread, and for that reason, some doctors keep Emtriva onboard in combination with those drugs after M184V resistance develops. In 2006, Emtriva was combined with Sustiva (efavirenz) and Viread (tenofovir) in one pill, which is known as Atripla. Emtriva oral solution should be kept in the refrigerator. If kept at room temperature, the oral solution should be used within three months. See package insert for more complete information on potential side effects and interactions.

Doctor's Comments

Few people take Emtriva itself; it's almost always combined with tenofovir in the form of Truvada, with tenofovir and efavirenz in the form of Atripla, or with tenofovir and rilpivirine in the form of Complera (with more co-formulations on the way). The characteristics of FTC are similar to those of 3TC (Epivir): it has the same resistance profile and is also safe and extremely well tolerated. The main difference between the two drugs is that FTC tends to be combined with tenofovir, while 3TC is usually taken in combination with AZT (Retrovir), abacavir (Ziagen), or both. Aside from the convenience of the co-formulations, there may be other reasons why these combinations make sense. Both tenofovir and FTC have similar half-lives, which are longer than those of other nucleoside analogs. This means they hang around longer in the blood and in CD4 cells. Combining two drugs with similar half-lives may help to prevent resistance if doses are missed or treatment is interrupted. Indeed, we seem to see less tenofovir resistance when tenofovir is combined with FTC than when it's combined with 3TC, a consideration that may become relevant now that 3TC is going generic.

-- Joel Gallant, M.D., M.P.H.

Activist's Comments

The "Quiet Giant" of the ARV world, the "son of 3TC" is much better than its dad. This beauty (FTC) is a great tool. It makes the virus "less fit," meaning less able to multiply and produce lots of harmless mutations, so it isn't as harmful as wild types. From personal experience, I have never heard anyone complaining about side effects from Emtriva, though it's hard to tell, as it is usually blended in with other drugs in compounds like Truvada, or once-daily single tablet regimens like Atripla or Complera. Long half life means it stays in the system longer. Because of its activity against hepatitis B virus, people should check with their doctors before using this drug to prevent HBV cross resistance or "flare-ups" when stopping the medication.

-- Joey Wynn

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