Reviewed by: HU Medical Review Board | Last reviewed: 5/31/22

Prezcobix is a combination medication that contains darunavir and cobicistat. It is used alongside other HIV medications as part of antiretroviral therapy (ART) for HIV-1 in adults who have never previously been treated for their HIV and pediatric patients weighing at least 40 kilograms. Patients who have previously taken HIV medications can still take Prezcobix, as long as they have no drug resistance mutations to darunavir (one of the ingredients in Prezcobix).

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 Prezcobix?

The main ingredients in Prezcobix are darunavir and cobicistat. Darunavir is a protease inhibitor (PI) and cobicistat is a CYP3A inhibitor, also referred to as a pharmacokinetic enhancer.

How does Prezcobix work?

During the HIV life cycle, the virus disassembles itself when it gets inside human host CD4 cells. The virus then undergoes reverse transcription and integration to join human host cell DNA, allowing for HIV’s genetic information to continue to get replicated. A form of this replicated genetic information is called messenger RNA (mRNA). mRNA is used to create proteins, including the enzymes HIV virions carry around with them in order to live.

How do protease inhibitors work?

During the process of converting mRNA into these proteins, the virus uses its protease enzyme. The protease enzyme cuts the mRNA into sections that will eventually be turned into the different proteins required for new, mature viruses to form. PIs inhibit this protease enzyme and prevent it from cutting the mRNA into its different parts. Without this cutting, or cleavage, of the mRNA, the final protein products aren’t able to be made and a mature virus cannot be formed and released into the blood to infect other cells.

How do pharmacokinetic enhancers work?

Pharmacokinetic enhancers don’t directly target and treat HIV. Instead, they inhibit an enzyme in the human body called cytochrome P450 3A4, also called CYP3A4. Normally, CYP3A4 helps break down drugs and other molecules in the body so that they can be eliminated.

Drugs that get broken down, or metabolized, by this enzyme are prevented from staying in the body for too long. However, when CYP3A4 is inhibited by a pharmacokinetic enhancer, it allows for the normal drug targets of this enzyme to continue to exist and work in the body beyond what’s normal. By preventing the breakdown enzyme from doing its job, the concentration and efficacy of other drugs, like darunavir, may be increased.

Possible side effects of Prezcobix

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

  • Diarrhea
  • Nausea
  • Headache
  • Abdominal pain
  • Vomiting
  • Rash

Things to consider before starting Prezcobix

As with any medication, there are several very rare but serious risks that need to be considered before taking Prezcobix. 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 Prezcobix include liver issues and skin reactions. 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 a serious skin reaction include the following:

  • Skin blisters or peeling
  • Mouth sores
  • Swelling of the lips, mouth, face, or throat
  • Fever
  • Redness or swelling of the eyes
  • Muscles or joint aches

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

There are many medications that can interact with Prezcobix and cause serious issues. It’s important to tell your healthcare provider about any medications you are currently taking, have recently taken, or plan to start taking. Prezcobix 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 Prezcobix. New or worsening diabetes and high blood sugar may also occur while taking Prezcobix.

Before starting Prezcobix, 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 diabetes
  • Have hemophilia
  • Are allergic to drugs called sulfa drugs (sulfonamide-containing medications)
  • 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

Prezcobix 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 Prezcobix. Prezcobix may also cause changes in body fat, especially around the breast, trunk, upper back, and neck regions. Individuals with hemophilia who take Prezcobix may experience increased bleeding.

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