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Cimduo

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). 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 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.

What are the possible side effects of Cimduo?

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

  • Headache
  • Pain
  • Depression
  • Rash
  • Diarrhea

Things to note about Cimduo

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 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

If you have hepatitis B virus and start taking Cimduo, your hepatitis B may get worse. 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. 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 hepatitis B virus
  • 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.

Dosing information

The most common dosage of Cimduo is one tablet taken by mouth once a day. A tablet contains 300 mg of lamivudine and 300 mg of tenofovir disoproxil fumarate. It is important to take your medication exactly as prescribed and to not stop or change your Cimduo dosage without talking to your healthcare provider first. Cimduo can be taken with or without food. If you miss a dose of Cimduo, take it as soon as you remember, but never take two at a time. If it is close to your next dosage time when you remember, just take your next dose only. If you take too much Cimduo, seek medical attention immediately.1,2

Written by: Casey Hribar | Last reviewed: September 2019
  1. Cimduo. United States Department of Health and Human Services: AIDSinfo. https://aidsinfo.nih.gov/drugs/593/cimduo/0/patient/. Published April 1, 2019. Accessed July 20, 2019.
  2. Cimduo Prescribing Information. United States Food and Drug Administration (US FDA). https://www.accessdata.fda.gov/drugsatfda_docs/label/2018/022141s000lbl.pdf. Published February 2018. Accessed July 20, 2019.