What to Know About Descovy (Emtricitabine, Tenofovir Alafenamide)

An updated version of Truvada offers fewer side effects

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Descovy is a two-in-one drug used to treat HIV in adults and children. The oral tablet contains emtricitabine (a.k.a. FTC) and tenofovir alafenamide fumarate (TAF), both of which belong to a class of drugs called nucleoside reverse transcriptase inhibitors (NRTIs).

NRTIs work by blocking an enzyme called reverse transcriptase that HIV needs to replicate. By doing so, the virus can be suppressed to undetectable levels, thereby preventing disease progression.

Hand holding a Descovy tablet
Gilead Sciences

Approved for the treatment of HIV by the U.S. Food and Drug Administration (FDA) in 2015, Descovy is used in combination with at least one other antiretroviral drug. There are no generic versions of Descovy and no liquid suspensions for children.

In October 2019, the FDA also approved Descovy for use in pre-exposure prophylaxis (PrEP), a preventive strategy used to reduce the risk of infection in people without HIV.

Descovy vs. Truvada

Descovy can be considered an "improved" version of Truvada, the latter of which contains tenofovir disoproxil fumarate (TDF) rather than TAF. Of the two, TAF delivers a smaller dose of tenofovir because it is a prodrug (an inactive substance that is converted by the body into an active drug). This helps reduce the risk of kidney toxicity experienced by some users of Truvada.

Uses

Descovy is used in combination antiretroviral therapy to treat HIV infection in adults and children who weigh at least 77 pounds (35 kilograms). Because the dose is fixed and cannot be modified, the drug cannot be used on anyone under 77 pounds due to the risk of toxicity.

Descovy can also be used on its own for PrEP in at-risk adults and adolescents who weigh at least 55 pounds (25 kilograms). According to the U.S. Preventive Services Task Force, those at increased risk of getting HIV include:

Before Taking

Descovy can be used in the first-line treatment of HIV or for those who have experienced treatment failure. In either instance, blood tests will be performed to determine whether you have any drug-resistant variants of HIV. Doing so helps select the combination of drugs best able to achieve viral suppression.

Even if you've just been infected, it is possible to pick up a drug-resistant virus through sex, shared needles, and other modes of transmission.

Two tests are standardly used to "profile" your virus:

  • Genetic resistance testing, the preferred option, can identify the types and number of mutations that confer resistance to specific antiretroviral drugs
  • Phenotypic testing, typically used with genetic resistance testing after a treatment failure directly exposes the virus to different antiretroviral drugs to see which work best

Precautions and Contraindications

Even if genetic and phenotypic testing reveals Descovy to be an effective treatment option, there may be certain conditions that contraindicate its use. Chief among them is a prior hypersensitive reaction to emtricitabine or tenofovir in either form.

Descovy may also need to be avoided or used with extreme caution in people with chronic kidney disease. Because the drugs are excreted through the kidneys, they may impair kidney function in those with pre-existing disease.

Descovy should not be used when the estimated creatinine clearance is below 30 milliliters per minute (mL/min). Values of this level indicate severe kidney dysfunction.

If Descovy is used for PrEP, the user should be screened for HIV prior to the initiation of therapy and at least every three months thereafter.

Other Combination Antiretroviral Drugs

In addition to Descovy, there are 21 other fixed-dose combination drugs used to treat HIV, 13 of which can be used on their own:

Dosages

Descovy is manufactured as a blue, rectangular-shaped, film-coated tablet embossed with "GSI" on one side and "225" on the other. Each tablet contains 200 milligrams (mg) of emtricitabine and 25 mg of TAF.

The recommended dose varies by the aims of therapy:

  • HIV treatment: One tablet daily taken by mouth with or without food in combination with at least one other antiretroviral drug
  • HIV PrEP: One tablet daily taken by mouth with or without food

How to Take and Store

Descovy tablets should be swallowed whole. The tablets should never be chewed, split, or crushed as this can affect drug absorption.

As with all HIV drugs, it is essential that you take your medication every day without interruption. Poor adherence remains the leading cause of treatment failure.

If you miss a dose, take it as soon as you remember. If it is close to the time of your next dose, skip the missed dose and continue as normal. Do not double-up doses in an effort to catch up.

Descovy can be stored at room temperature, ideally below 86°F (30°C). Keep the pills in their original light-resistance container along with the silica desiccant packet to prevent moisture damage. Discard any Descovy tablets that have expired.

Side Effects

Although side effects are common with all drugs, newer-generation NRTIs like Descovy offer far fewer than those of the past. Even so, there are rare instances in which Descovy can cause severe and even life-threatening side effects.

Common

The side effects of Descovy tend to be mild and resolve with a week or two as your body adapts to treatment. The most common (by order of frequency) are:

  • Diarrhea (5% of users)
  • Nausea (4% of users)
  • Headache (2% of users)
  • Stomach upset (2% of users)
  • Fatigue (2% of users)

In 2020, the DISCOVER revealed that TAF could cause high cholesterol (hypercholesterolemia), a side effect not seen with TDF. As such, blood lipid tests should routinely be performed while taking Descovy or any other TAF-based therapy.

In fewer than 1% of cases, Descovy may cause a drug allergy. Most cases are and not require the interruption of treatment. Anaphylaxis (a potentially deadly, all-body reaction) is a rare occurrence with Descovy.

Severe

Based on prior experience with emtricitabine and tenofovir, researchers have identified five rare but potentially severe side effects of Descovy to watch out for:

Acute Kidney Failure

Descovy is less impactful on the kidneys than Truvada but can still cause new or worsening kidney impairment in some. On rare occasions, kidney failure may occur (although this tends to be reversible once Descovy is stopped).

Acute kidney impairment is often asymptomatic and may only be detected with routine renal function tests. If symptoms do develop, they may include:

If left untreated, acute kidney failure can lead to seizures, coma, and death.

Bone Density Loss

As with kidney impairment, bone mineral density (BMD) loss is more common with Truvada than with Descovy.

With that said, as many as 10% of Descovy users will experience bone loss of greater than 5% in the lumbar spine, while 7% will experience greater than 7% loss in the neck after just 48 weeks of treatment.

While the short-term impact is considered modest in adults, the loss of BMD in children is concerning. This level of bone loss during adolescence can significantly increase the risk of fractures (including spinal and hip fractures) in later adulthood.

Because bone loss are often asymptomatic, some doctors recommend occasional dual-energy X-ray absorptiometry (DEXA) scans for children on long-term tenofovir-based therapies.

Lactic Acidosis

FTC and TAF can both cause a build-up of a waste product known as lactic acid in the bloodstream. People who are obese or have used NRTIs for many years may be at increased risk of developing a serious and potentially life-threatening condition called lactic acidosis.

Symptoms of lactic acidosis include:

  • Nausea
  • Vomiting
  • Abdominal pain
  • Diarrhea
  • Extreme fatigue
  • Dizziness or lightheadedness
  • Muscle pain
  • Cold sensations

NRTI-induced lactic acidosis typically occurs anywhere from 4 to 28 weeks of starting treatment. If symptoms like these develop while taking Descovy, call your doctor immediately.

Immune Reconstitution Inflammatory Syndrome (IRIS)

FTC has been known in rare cases to trigger a condition called immune reconstitution inflammatory syndrome (IRIS). This occurs when the immune system starts to recover but then suddenly overacts to a latent or asymptomatic opportunistic infection.

The excessive inflammatory response may either "unmask" a previously undiagnosed infection or cause the worsening of a diagnosed one. Tuberculosis, cytomegalovirus (CMV), and pneumocystis pneumonia are opportunistic infections commonly associated with IRIS.

IRIS tends to affect people who start antiretroviral therapy when their immune systems are severely compromised (typically with a CD4 count under 50). People with low CD4 counts should be monitored closely once Descovy is started so that any emerging infection can be spotted and treated immediately.

IRIS tends to develop within four to eight weeks of starting therapy. With a mortality rate of 15% to 75%, early identification is vital to preventing serious complications.

Warnings and Interactions

Descovy carries a black box warning advising consumers and healthcare professionals of the risk of hepatitis B reactivation upon the discontinuation of FTC or TAF. A black box warning is the highest level of advisement from the FDA.

The discontinuation of FTC or TAF has been known to cause the reactivation of hepatitis symptoms in people co-infected with HIV and hepatitis B. In rare cases, liver failure and permanent liver damage have been known to occur.

Although Descovy is not contraindicated for use in people with liver disease, careful consideration is needed to weigh the benefits and risks of treatment and decide whether other antiretroviral drugs may be more appropriate. People with cirrhosis and advanced liver disease are at greatest risk.

Pregnancy and Breastfeeding

FTC and TAF are both classified as Pregnancy Category B drugs. While Category B drugs are generally considered safe for use during pregnancy, there are few well-controlled studies in humans evidencing their long-term safety. If you are pregnant or in your childbearing years, speak with your doctor to fully understand the benefits and risks of treatment.

In the United States, breastfeeding is not recommended for mothers with HIV irrespective of their treatment status, CD4 count, or viral load.

Drug-Drug Interactions

There are a number of drugs that can interact with Descovy. Several of these are regulated by the same protein—called P-glycoprotein (P-gp)—that Descovy relies on for transport throughout the body. Competition for P-gp can cause Descovy concentrations to drop, often a point where the drug's effectiveness is compromised.

Descovy should never be used with the following drugs:

By contrast, certain antifungal drugs can increase the concentration of Descovy and, with it, the risk of side effects. These include the drugs Nizoral (ketoconazole) and Sporanox (itraconazole).

Care should be taken when using Descovy with other drugs that cause kidney impairment, the combined use of which can cause acute renal failure. These include:

In some cases, your doctor may be able to overcome an interaction by adjusting the dose or separating doses by several hours. At other times, a drug substitution may be needed.

To avoid interactions, advise your doctor about any drugs you take, whether they are prescription, over-the-counter, herbal, nutritional, or recreational.

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