Symtuza (darunavir/cobicistat/emtricitabine/tenofovir alafenamide) is a prescription drug used to treat HIV infection. Symtuza can cause side effects that range from mild to serious. Examples include diarrhea, skin rash, and nausea.

Specifically, Symtuza is used in adults and children weighing at least 40 kilograms (kg) to treat HIV-1 infection. (For reference, 1 kg equals about 2.2 pounds.) Symtuza is typically prescribed for people with no previous history of HIV medication use.

If you’re switching from other HIV treatments to Symtuza, you’ll need to meet the following criteria:

  • HIV viral load (amount of HIV in your blood) is less than 50 copies per milliliter (mL)
  • no changes to HIV treatment within the past 6 months
  • HIV still responds well to darunavir or tenofovir (two of the active ingredients in Symtuza)

Symtuza comes as an oral tablet and contains the active ingredients darunavir, cobicistat, emtricitabine, and tenofovir alafenamide.

Keep reading to learn about common, mild, and serious side effects Symtuza can cause. For a general overview of the drug, including details about its uses, see this article.

Symtuza has a boxed warning. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). For details, see the “Side effects explained” section.

Some people may experience mild to serious side effects during Symtuza treatment. Examples of the drug’s commonly reported side effects include:

Mild side effects have been reported with Symtuza. These include:

In most cases, these side effects should be temporary. And some may be easily managed. But if you have symptoms that are ongoing or bothersome, talk with your doctor or pharmacist. And do not stop Symtuza treatment unless your doctor recommends it.

Symtuza may cause mild side effects other than those listed above. See the drug’s prescribing information for details.

Serious side effects have been reported with Symtuza. These include:

If you develop serious side effects while taking Symtuza, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

* To learn more about this side effect, see the “Side effects explained” section.

Note: After the FDA approves a drug, it tracks and reviews side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Symtuza, visit MedWatch.

Allergic reaction

For some people, Symtuza can cause an allergic reaction, but this side effect was rarely reported in the drug’s studies.

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment to manage your symptoms and can determine whether you should continue Symtuza treatment.

If you have symptoms of a severe allergic reaction, such as swelling or difficulty breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms you’ve had a serious allergic reaction to Symtuza, they may have you switch to a different treatment.

Get answers to some frequently asked questions about Symtuza’s side effects.

How do side effects of Symtuza compare with those of Biktarvy?

Similar side effects have been reported with Symtuza and Biktarvy. This is likely because they each contain two of the same active ingredients: emtricitabine and tenofovir alafenamide.

Some of the most common side effects reported in Symtuza studies and Biktarvy studies include diarrhea, nausea, and headache.

For additional information about how Symtuza compares with other HIV medications, talk with your doctor.

Does Symtuza cause long-term side effects?

It may. Long-term side effects include those that may start at any time you’re taking a drug, even if you’ve taken it for a long time. It also includes side effects that may not go away, even after you stop taking the drug.

Examples of long-term side effects reported in Symtuza’s studies include:

  • changes in body fat
  • kidney problems, including kidney failure

Talk with your doctor to learn more about possible side effects of Symtuza and how long they may last.

Can Symtuza cause weight gain?

It’s not likely. Weight gain wasn’t a side effect reported in Symtuza studies.

However, loss of appetite that can result in weight loss is a possible side effect of Symtuza.

Talk with your doctor if you have additional questions about how Symtuza may affect your weight.

Learn more about some of the side effects Symtuza may cause.

Risk of worsening HBV infection

There’s a boxed warning for the risk of worsening HBV infection with Symtuza. A boxed warning is the most serious warning from the FDA. It alerts doctors and patients about drug effects that may be dangerous.

For people with an HBV infection, stopping certain HIV medications can worsen symptoms of hepatitis B. This was a serious side effect reported in studies of people who stopped emtricitabine and tenofovir. (These are two of the active ingredients in Symtuza.) So it’s possible that Symtuza can also cause this side effect.

Worsening HBV infection may cause other problems, such as liver failure. And liver failure can cause symptoms such as:

What might help

Before you start Symtuza, your doctor will order an HBV test for you. They’ll also monitor your liver enzymes during your treatment with Symtuza.

If you have HBV, it’s important to take Symtuza as directed. Be sure to refill your prescriptions on time so that you don’t run out. Do not skip or miss a dose of Symtuza, as this can allow the virus to develop resistance to the drug. This makes the HBV infection more difficult to treat.

If you need to stop taking Symtuza, talk with your doctor first. They’ll likely continue monitoring your liver enzymes for at least several months after you’ve stopped the drug. They may need to prescribe medications to treat your hepatitis B.

Talk with your doctor if you experience any of the above symptoms after stopping Symtuza.

Liver problems

Liver problems, including liver inflammation, were serious side effects reported in studies of darunavir. (This is one of the active ingredients in Symtuza.) So, Symtuza may also carry a risk for liver damage.

Liver inflammation may cause symptoms such as:

  • tiredness
  • loss of appetite
  • jaundice
  • increased liver enzymes
  • dark urine
  • loss of appetite

Factors that can increase the risk of liver problems when taking Symtuza include having any liver problems, such as active hepatitis B or hepatitis C. Excessive alcohol consumption (if applicable) can also worsen liver function and can lead to liver problems.

What might help

Your doctor will order liver function tests before and during your treatment with Symtuza. They’ll also test you for the presence of hepatitis B before prescribing this drug. Be sure your doctor is aware of any liver problems you have.

If you experience any of the above symptoms during Symtuza treatment, talk with your doctor right away.

Keeping track of side effects

During your Symtuza treatment, consider taking notes on any side effects you’re having. You can then share this information with your doctor. This is especially helpful when you first start a new drug or combination of treatments.

Your side effect notes can include things such as:

  • what dose of the drug you were taking when you had the side effect
  • how soon you had the side effect after starting that dose
  • what your symptoms were
  • how your symptoms affected your daily activities
  • what other medications you were taking
  • any other information you feel is important

Sharing notes with your doctor will help them learn more about how Symtuza affects you. They can then use this information to adjust your treatment plan if needed.

Below is important information you should consider before starting Symtuza.

Boxed warning: Risk of worsening hepatitis B

Symtuza has a boxed warning for the risk of worsening hepatitis B. A boxed warning is the most serious warning from the FDA. For details, see the “Side effects explained” section.

Other warnings

Symtuza can sometimes cause harmful effects in people with certain conditions. This is known as a drug-condition interaction. Other factors may also affect whether this drug is a good treatment option for you.

Talk with your doctor about your health history before starting Symtuza. Be sure to tell them if any of the following factors apply to you:

  • liver problems, including HBV infection
  • kidney problems
  • diabetes
  • hemophilia
  • sulfa allergy
  • previous allergic reaction to Symtuza
  • taking certain medications*
  • pregnancy
  • breastfeeding
  • alcohol consumption

* To learn more about certain medications that interact with Symtuza, see this article.

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.