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

Cimduo is a combination medication that contains lamivudine and tenofovir disoproxil fumarate. It is used with other antiretroviral agents as a part of antiretroviral therapy (ART) for HIV-1 in individuals who weigh at least 77 pounds (35 kg).

Cimduo should only be used in individuals with confirmed HIV-1 and no prior antiretroviral treatment history or known resistance to the components of Cimduo. It is not effective against HIV-2.

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, called viral load.

What are the ingredients in Cimduo?

The main ingredients in Cimduo are lamivudine and tenofovir disoproxil fumarate. Both ingredients are nucleoside reverse transcriptase inhibitors (NRTIs).

How does Cimduo work?

Cimduo is a combination of two 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 Cimduo include, but are not limited to:

  • Headache
  • Pain
  • Depression
  • Rash
  • Diarrhea

These are not all the possible side effects of Cimduo. Talk to your doctor about what to expect when taking Cimduo. You also should call your doctor if you have any changes that concern you when taking Cimduo.

Things to consider

Cimduo 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.

As with any medication, there are several very rare but serious risks that need to be considered before taking Cimduo. 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.

Several of these rare but serious side effects of Cimduo include liver issues, including liver failure, 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, vomiting
  • Yellowing of the whites of the eyes or skin
  • Light-colored bowel movements
  • Pain or tenderness in your abdomen or 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
  • Pain in your muscles or abdomen
  • Nausea and vomiting
  • Irregular or fast heartbeat
  • Difficulty breathing

If you have hepatitis B virus (HBV) and start taking Cimduo, your HBV may get worse. Cimduo contains lamivudine, which can cause HBV reactivation in individuals who have both HIV and HBV infections. Prior to starting Cimduo, your healthcare provider will assess your HBV status. They will also closely monitor you during treatment.

Cimduo can impact liver function. Medications that are known to affect liver enzymes, such as certain antifungal medications or certain antibiotics, should be used with caution and monitored closely by your healthcare provider.

Cimduo should not be taken with atazanavir and sorbitol.

Rarely, Cimduo may also cause new or worsening kidney issues. This includes an increased risk of kidney failure. Your healthcare provider will need to monitor your kidney function before you start and while taking Cimduo. Tenofovir disoproxil fumarate, one of the components of Cimduo, can affect kidney function. If you have to use other drugs that impact kidney function, such as nonsteroidal anti-inflammatory drugs (NSAIDs) or certain antibiotics, use caution and check with your doctor first.

Bone issues may also happen while taking Cimduo, including, but not limited to, bone pain, thinning, or softening. These problems may lead to bone fractures.

Some children taking Cimduo may have an increased risk of developing pancreatitis. Signs of pancreatitis include, but are not limited to, nausea, vomiting, and severe upper-stomach-area pain.

Cimduo may also cause changes in body fat, especially around the breast, trunk, upper back, and neck regions.

Before starting Cimduo, tell your doctor if you:

  • Have or previously had HBV
  • Have or previously had hepatitis C virus
  • Have a history of liver or kidney problems
  • Have a history of bone problems
  • 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

Cimduo 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 Cimduo. These are not all the possible side effects of Cimduo. Patients should talk to their doctor about what to expect with treatment with Cimduo.

By providing your email address, you are agreeing to our privacy policy.