Brand name: Epzicom
Generic name: abacavir sulfate (abacavir)/lamivudine, or ABC/3TC
Class: Nucleoside reverse transcriptase inhibitor
Manufacturer: ViiV Healthcare, www.viivhealthcare.com, (877) 844-8872
Standard Dose: One tablet (600 mg abacavir/300 mg lamivudine), once a day, with or without food, with no dietary restrictions. 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. Not indicated for patients younger than 18 years old, those with kidney function less than 50 mL/min, and those with liver problems, because dose adjustments are not possible with this fixed dose combination.
Potential side effects and toxicity: The most common side effects of Epzicom are the same as the individual drugs it contains -- see Epivir (lamivudine) and Ziagen (abacavir). Of note is the hypersensitivity reaction (HSR, an allergic-like reaction) warning on abacavir (see Ziagen page). A simple and inexpensive blood test for HLA-B*5701 (a genetic marker) can identify people at high risk for this reaction and virtually eliminate HSR. About 90% of HSR occurs within the first six weeks of treatment. Symptoms of HSR usually worsen, very slowly, with every dose. If treatment is stopped because of this serious reaction, you can never take products containing abacavir, such as Epzicom or Trizivir, again (called "re-challenging"). Re-challenging could cause a rare life-threatening reaction. (This does not apply to missed doses when there's no HSR, but watch for symptoms if you've stopped the drug for at least a few days.) Symptoms usually, but not always, include some combination of fever; muscle ache; malaise (general ill feeling); severe nausea, vomiting, diarrhea, or abdominal pain; severe tiredness; respiratory symptoms (cough, difficulty breathing, and sore throat); and possible rash. Symptoms are listed on the patient information sheet and warning card that you receive each time you fill your prescription. You should keep the warning card with you. Hypersensitivity might be confused with flu during flu season, but remember that HSR worsens with every dose. Check with your doctor if you have any side effects after taking this medicine -- don't just stop! Some observational studies seemed to indicate that abacavir may increase the risk of cardiovascular events, including heart attacks, in people with greater risk factors (such as smoking, diabetes, high blood pressure, and drug use). One possible explanation was found -- people with kidney problems were put on abacavir in order to avoid tenofovir, which has potential for kidney toxicity, and those people already had a strong risk for heart problems. The FDA conducted an analysis of 26 randomized clinical trials that evaluated abacavir. This analysis did not show an increased risk of heart attacks associated with the use of abacavir. Last year, DHHS HIV treatment guidelines added the statement, "to date, no consensus has been reached either on the association of [abacavir] use with MI [myocardial infarction, or heart attack] risk or a possible mechanism for the association." People who have high risk for heart disease are monitored more closely and the decision to stop or never start a regimen containing abacavir is up to you and your provider. See chart for potential drug class side effects.
Potential drug interactions: See the individual drugs contained in Epzicom, Epivir and Ziagen, for more information. Do not take Epzicom with Atripla, Combivir, Complera, Emtriva, Epivir, Epivir-HBV, Trizivir, Truvada, or Ziagen, since all or part of these medications are already in Epzicom or have equivalent medications. Alcohol can increase the levels of abacavir and therefore increase the possibility of side effects.
More information: Currently, U.S. HIV treatment guidelines recommend Truvada over Epzicom as the preferred backbone for the NRTI component of an HIV drug combination for first-time therapy. Epzicom is listed as an alternative NRTI backbone. Study ACTG 5202 reported that for those people who started treatment with a viral load of more than 100,000, Epzicom was "significantly less effective at controlling HIV" in the regimens tested. Moreover, time to a serious adverse event was sooner in the people taking Epzicom. These efficacy and safety findings were not confirmed in a manufacturer-sponsored study, HEAT, another large study comparing Epzicom and Truvada. Still, in HIV therapy, there is always use for an alternative choice of drugs. The DHHS guidelines state, "Pending additional data, [Epzicom] should be used with caution in individuals who have plasma HIV RNA [viral load] greater than 100,000 copies/mL, as well as in persons at higher risk for cardiovascular disease. However, Epzicom remains a good alternative dual-NRTI option for some treatment-naïve patients." Remember, too, that Truvada has its own side effect and drug interaction issues, although it's famed for its tolerability. The HLA-B*5701 test should never be used to diagnose HSR. Do not use a skin patch test to confirm HSR. Regardless of the results, it is important to monitor the potential for this reaction. If HSR is suspected or cannot be ruled out, products containing abacavir should be discontinued. The incidence of HSR was the same between Epzicom once-daily and Ziagen twice-daily (8% vs. 9%), but the incidence of severe reactions was higher with Epzicom (5% vs. 2%). Remember that the HSR cited may have been suspected, not definitely diagnosed. The lamivudine portion of Epzicom is also used to treat the hepatitis B virus (HBV); see Epivir page. If you are co-infected with HIV and HBV and you stop Epzicom, your HBV may reactivate and you may experience signs and symptoms of acute HBV. You should be closely monitored by your physician. See package insert for more complete information on potential side effects and interactions.
Epzicom is the safe, well-tolerated, once-daily co-formulation of abacavir (Ziagen) and 3TC (Epivir). It's generally viewed as the best alternative to Truvada when tenofovir can't be used (usually for reasons having to do with the kidneys). The issues of abacavir hypersensitivity (see Ziagen) apply to Epzicom as well, so an HLA-B*5701 test should always be ordered before taking this drug. Epzicom appears to be somewhat less effective than Truvada in people with viral loads above 100,000. For reasons discussed elsewhere, we also tend to avoid Epzicom in people who are at high risk of coronary heart disease.
-- Joel Gallant, M.D., M.P.H.
A combination of abacavir and lamivudine, Epzicom was a convenient once-a-day improvement over Combivir, or so we thought. Complications, side effects, and risk of coronary issues have made this far less prescribed than in prior years. As it fades out of favor, it leaves us with a mediocre backup tool for those failing all of the latest greatest therapies.
-- Joey Wynn
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