Reviewed by: HU Medical Review Board | Last reviewed: March 2023

Trizivir is a combination medication that contains abacavir, lamivudine, and zidovudine. It is used with other antiretroviral agents as a part of antiretroviral therapy (ART) for HIV-1 in individuals who are at least 88 pounds (40 kg). Although it is not a cure for HIV, when taken as directed, it allows for the virus to be suppressed. This prevents further transmission of HIV and allows an individual’s immune system to improve through increasing CD4 cell counts and decreasing the amount of active virus in the blood (viral load).

What are the ingredients in Trizivir?

The main ingredients in Trizivir are abacavir, lamivudine, and zidovudine. All three ingredients are nucleoside reverse transcriptase inhibitors (NRTIs).

How does Trizivir work?

Trizivir is a combination of three NRTI medications. NRTIs stop the reverse transcription step of the HIV life cycle. Normally, HIV uses its reverse transcriptase enzyme to build a strand of DNA from its original RNA form. In order to do this, it uses genetic building blocks called nucleosides that come from the host cell. These nucleosides are strung together one at a time, like beads on a string, to create the final DNA product.

NRTIs act as nucleoside mimics that stop the DNA-building process. NRTIs look like normal nucleosides, except they’re missing a special chemical group on one side. Without this group, the reverse transcriptase enzyme is unable to attach more nucleosides to the chain after them. This prevents the full string of DNA from being formed, preventing HIV RNA from making it all the way through the reverse transcription process and into host DNA for further replication.

Possible side effects

The most common side effects of Trizivir include, but are not limited to:

  • Nausea
  • Headache
  • Weakness
  • Tiredness
  • Vomiting

Things to note

As with any medication, there are several very rare but serious risks that need to be considered before taking Trizivir. Trizivir has a boxed warning, the strictest warning from the US Food and Drug Administration (FDA). It has this warning because of the possibility of serious side effects as described below.

Your healthcare provider can help determine what issues you may be at risk for and help determine what treatment options are the safest for you. It’s also important to remember that the risk of one or more of these issues occurring is low, and the benefits of treating the virus often greatly outweigh the risks.

Allergic reactions

One of the ingredients in Trizivir, abacavir, can cause severe allergic reactions in certain individuals. Although this is very rare, it is especially true for individuals with a gene mutation called HLA-B*5701. A blood test can be used to determine if someone has this mutation before starting the medication. An individual may be having an allergic reaction if they have a symptom from two or more of the following categories:

  • Fever
  • Rash
  • Abdominal pain, diarrhea, nausea, vomiting
  • Extreme tiredness, achiness, or a feeling of generally being ill
  • Sore throat, cough, shortness of breath

If you have or think you may have an allergic reaction to Trizivir, seek medical attention immediately and never restart Trizivir or another abacavir-containing product, as serious events including death may occur. If you stop Trizivir for any reason, tell your healthcare provider before starting the medication again.

Other side effects of Trizivir

Rarely, Trizivir may impact an individual’s red and white blood cells. Low red blood cell counts (anemia) and low numbers of a specific kind of white blood cell called neutrophils (neutropenia) may occur. This is especially true for individuals with more advanced HIV. Blood counts should be regularly monitored while taking Trizivir. Trizivir may also cause muscle weakness or pain, called myopathy.

Several other rare but serious side effects of Trizivir include liver issues and an increase of lactic acid in the blood (lactic acidosis). Signs of liver issues include, but are not limited to:

  • Dark-colored urine
  • Loss of appetite
  • Nausea
  • Yellowing of the whites of the eyes or skin
  • Light-colored bowel movements
  • Pain or tenderness on the right side of your stomach

Signs of lactic acidosis include, but are not limited to:

  • Trouble breathing
  • Feeling cold, especially in the limbs
  • Dizziness or lightheadedness
  • Feeling tired or weak
  • Muscle pain
  • Nausea and vomiting
  • Irregular or fast heartbeat

Although rare, Trizivir may also increase an individual’s risk of having a heart attack. It is important to tell your healthcare provider if you have any heart issues or have had heart issues in the past. Also, if you have hepatitis B virus and start taking Trizivir, your hepatitis B may get worse.

Before starting Trizivir, tell your doctor if you:

  • Have or previously had hepatitis B virus
  • Have or previously had hepatitis C virus
  • Have low blood cell counts or a history of a bone marrow problem
  • Have a history of liver, heart, or kidney problems
  • Have a history of high blood pressure, high cholesterol, or diabetes
  • Are a smoker
  • Drink alcohol or take medicine with alcohol in them
  • Are pregnant or planning to become pregnant
  • Are breastfeeding or planning to breastfeed
  • Are taking any over-the-counter vitamins, supplements, medicines, or herbal remedies
  • Are on any other medications or are about to start any other medications, including hormonal birth control or medications for hepatitis viruses

Trizivir may cause a condition called IRIS (immune reconstitution inflammatory syndrome). IRIS occurs when an individual’s immune system gets stronger after being weak and responds aggressively to previously hidden infections. This heightened response may make the person fighting the infection feel worse. Alert your healthcare provider immediately if you begin to have new symptoms after taking Trizivir.

Trizivir may also cause changes in body fat, especially around the breast, trunk, upper back, and neck regions. These are not all the possible side effects of Trizivir. Patients should talk to their doctor about what to expect with treatment with Trizivir.

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