What to Know About Descovy (Emtricitabine, Tenofovir Alafenamide)

An updated version of Truvada offers fewer side effects

Descovy (emtricitabine and tenofovir alafenamide fumarate) is a two-in-one drug used to treat human immunodeficiency virus (HIV) infection. Both emtricitabine and tenofovir alafenamide fumarate (TAF) belong to a class of drugs called nucleoside reverse transcriptase inhibitors (NRTIs) that prevent the virus from "hijacking" the DNA of the infected host cell and turning it into an HIV-generating factory.

Descovy is used in combination with other antiretroviral drugs to block the replication of HIV. By doing so, it stops the virus from killing defensive white blood cells, called CD4 T-cells, that the body needs to protect itself. Descovy only comes in a tablet form; there are no oral suspensions for younger children.

In October 2019, the U.S. Food and Drug Administration also approved Descovy for use in pre-exposure prophylaxis (PrEP), a strategy to reduce the risk of infection in HIV-negative people.

Pharmacist Holding Out a Packaged Prescription stock photo
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Descovy was approved by the U.S. Food and Drug Administration (FDA) on April 4, 2016, for use in adults and children who are old enough to swallow pills.

Descovy can achieve higher blood concentrations at lower doses than Truvada (emtricitabine and tenofovir disoproxil fumarate), an earlier version of the drug.

Compared to the "original" tenofovir disoproxil fumarate (TDF), which is dosed at 300 milligrams (mg) daily, tenofovir alafenamide fumarate (TAF) only requires 25 mg to achieve the same effects. The lower dose greatly reduces the risk of bone and kidney side effects associated with the earlier-generation drug.

Descovy is never used on its own. Combination antiretroviral therapy typically consists of a minimum of three drugs of at least two different drug classes. Anything less will not only decrease the likelihood of viral suppression but increase the risk of premature drug resistance and treatment failure.

The only exception is the two-in-one drug Juluca (rilpivirine and dolutegravir) which the FDA approved as a standalone treatment for HIV on November 21, 2017.

Descovy (or any other antiretroviral drug) does not cure HIV; it simply controls the virus and prevents the disease from progressing and causing symptoms.

Other Uses

In October 2019, the Antimicrobial Drug Advisory Committee of the FDA recommended that Descovy be approved for use in pre-exposure prophylaxis (PrEP), a strategy in which an antiretroviral drug is taken daily to reduce your risk of getting HIV. It's the second drug after Truvada to receive such approval.

Descovy is approved for use as PrEP in all at-risk adults and adolescents weighing at least 77 pounds (35 kilograms) with the exception of women who engage in vaginal sex due to lack of research supporting such use.

It can be used, however, in women who engage in anal sex.

Before Taking

Descovy can be used in newly treated people or those who have failed on other antiretroviral medication. In the United States, a blood test (known as genetic resistance testing) is typically performed to identify any antiretrovirals you may be resistant to.

Although Descovy resistance is unlikely in newly treated people, multi-drug resistant viruses have been known to be passed from infected to non-infected persons. It is for this reason that genotyping is performed in both newly treated and treatment-experienced people.

Precautions and Considerations

Descovy may cause hepatitis B symptoms to flare if and when the drug is stopped. To avoid this, a hepatitis B surface antibody (HBsAb) test would be ordered before the start of treatment to determine if you have been infected. Liver function tests will be used to check the status of your liver since flares tend to occur in people with advanced liver disease.

Renal enzymes would also be tested to check how well your kidneys are functioning. Since tenofovir is cleared from the body through urine, any impairment of the kidneys may cause the drug to accumulate to toxic levels.

If kidney impairment is severe—defined as a creatinine clearance of under 30 milliliters (mL) per minute—Descovy should be avoided.

Tenofovir and emtricitabine are both classified as Pregnancy Category B drugs. While Category B drugs are generally considered to be safe, there is only limited data on the safety of TAF during pregnancy. If you are pregnant or in your childbearing years, speak with your doctor to fully understand the benefits and risks of Descovy during pregnancy.

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


Descovy is a fixed-dose combination (FDC) drug containing 200 mg of emtricitabine and 25 mg of TAF. The film-coated tablets are blue, rectangular-shape, and embossed with "GSI" on one side and "225" on the other.

The recommended dosage of Descovy is one tablet taken daily by mouth with or without food. It can be used in adults as well as children weighing at least 55 pounds (25 kilograms). Children of this size should be able to swallow tablets.

How to Take and Store

Descovy tablets should be swallowed whole. The tablets should never be chewed, split, or crushed.

As with all HIV drugs, it is vital that you take your medication every day without fail (ideally at the same time to build a pill-taking habit). Suboptimal adherence remains the primary 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 degrees F (30 degrees C). Keep the pills in their original 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. Common side effects tend to be mild and may include:

  • Headache
  • Stomach upset
  • Dizziness
  • Nausea
  • Vomiting
  • Joint aches
  • Insomnia

The DISCOVER research trial has discovered that a new side effect present with TAF treatment is hypercholesterolemia. This effect is not present with the original TDF, however.

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

Most side effects will resolve on their own over several days or weeks as your body adapts to the medication. Others are imminently more serious and may require urgent medical intervention.

Kidney Impairment

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

Acute kidney impairment is often invisible 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 being said, as many as 10% of Descovy users will experience bone loss of greater than 5% in the lumbar spine, while 7% will experience bone loss of greater than 7% in the neck after just 48 weeks of treatment. Tenofovir is considered the culprit.

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

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

Lactic Acidosis

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

Symptoms of lactic acidosis include:

  • Nausea
  • Vomiting
  • Abdominal pain
  • Diarrhea
  • Extreme fatigue
  • Dizziness or lightheadedness
  • Muscle pain, often described as a burning ache
  • Cold sensations, especially in the arms and legs

If these symptoms occur while taking Descovy, call your doctor right away.

Immune Reconstitution Inflammatory Syndrome (IRIS)

Emtricitabine 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 non-symptomatic 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

The discontinuation of emtricitabine or tenofovir has been known to cause the reactivation of hepatitis B 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, the risk is clearly greater in those with cirrhosis or advanced liver disease. Careful consideration is required to weigh the benefits and risks of Descovy and whether other antiretroviral drugs may be more appropriate in this population.

Hepatitis B exacerbation can usually be recognized by the following symptoms:

  • Fever
  • Extreme fatigue
  • Abdominal pain in the upper right quadrant beneath the ribs
  • Dark urine
  • Pale stool
  • Joint and/or muscle pain
  • Loss of appetite
  • Nausea
  • Vomiting
  • Jaundice (yellowing of the skin or eyes)

In people with advanced liver disease or compensated cirrhosis (in which the liver is damaged but still functioning), hepatitis B therapy should be considered if Descovy is stopped, since acute exacerbations may lead to liver decompensation and failure.

Never stop taking Descovy without first speaking with your doctor.

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.

Among the drugs of concern are:

  • Anticonvulsant drugs used to treat seizures, including Tegretol (carbamazepine), Trileptal (oxcarbazepine), Dilantin (phenytoin), and phenobarbital
  • Anti-mycobacterial drugs used to treat tuberculosis, including rifampin, rifapentine, and rifabutin
  • Aptivus (tipranavir) plus Norvir (ritonavir), a drug combination commonly used to treat HIV
  • St. John's wort (Hypericum perforatum), a popular herbal remedy

The combined use of Descovy with any of these drugs is not recommended.

Care should also be taken with drugs that reduce kidney function, the combined use of which may cause acute kidney failure. Chief among these are:

  • Antiviral drugs such as Zovirax (acyclovir), Zirgan (ganciclovir), Valtrex (valacyclovir), cidofovir, and valganciclovir
  • Aminoglycoside antibiotics such as Gentak (gentamicin), tobramycin, streptomycin, neomycin, and paromomycin
  • Nonsteroidal anti-inflammatory drugs (NSAIDs), such as Advil (ibuprofen) and Aleve (naproxen), if used in high doses and/or in combination with other NSAIDs

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

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

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

A Word From Verywell

The wholesale price of Descovy in the United States is around $1,844 for a 30-day supply. While most insurance companies will cover some of the cost of Descovy, the copay or coinsurance costs may still be prohibitive.

If faced with high out-of-pocket expenses, you may be qualified to enroll in a copay assistance program (CAP), in which part or all of your copay costs are covered, or a patient assistance program (PAP), in which all costs may be covered for eligible families or individuals.

To find which drug assistance programs you qualify for, contact Gilead Advancing Access at 1-800-226-2056, Monday through Friday from 9:00 a.m. to 8.00 p.m. Eastern time.

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Article Sources
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