Tenofovir is an antiviral medicine that is used to treat HIV, the virus that can cause acquired immunodeficiency syndrome (AIDS). Tenofovir is not a cure for HIV or AIDS.

Tenofovir is also used to treat chronic hepatitis B.

Tenofovir is for use in adults and children at least 2 years old and weighing at least 22 pounds (10 kilograms).

Tenofovir may also be used for purposes not listed in this medication guide.

If you've had hepatitis B, it may come back or get worse after you stop using tenofovir. You may need liver function tests for several months.

Do not change your dose or stop using a medicine without your doctor's advice.

Before you start treatment with tenofovir, your doctor may perform tests to make sure you do not have HIV (if you are being treated for hepatitis B) or hepatitis B (if you are being treated for HIV).

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

Take tenofovir at the same time each day.

Some forms of tenofovir should be taken with food. Carefully follow all instructions on your medicine label.

Tenofovir oral powder should be mixed with soft food such as applesauce, yogurt, or baby food. Do not mix the oral powder with liquid.

Swallow the tablet whole and do not crush, chew, or break it. Tell your doctor if you or your the child taking tenofovir has trouble swallowing a tablet.

Doses are based on weight in children. Your child's dose needs may change if the child gains or loses weight.

You will need medical tests.

Use all HIV medications as directed. Do not change your dose or stop using a medicine without your doctor's advice. Remain under the care of a doctor.

Store tightly closed at room temperature, away from moisture and heat.

If you've had hepatitis B, it may come back or get worse after you stop using tenofovir. You may need liver function tests while using this medicine and for several months after you stop.

You should not take tenofovir if you are allergic to it.

Do not take tenofovir together with adefovir (Hepsera), or with combination medicines that contain tenofovir (Atripla, Biktarvy, Cimduo, Complera, Descovy, Genvoya, Odefsey, Stribild, Symfi, or Truvada).

Tell your doctor if you have ever had:

• liver disease (especially hepatitis B if you also have HIV);

• HIV (if you are taking tenofovir to treat hepatitis B);

• kidney disease; or

• low bone mineral density.

You may develop lactic acidosis, a dangerous build-up of lactic acid in your blood. Ask your doctor about your risk.

To prevent HIV in a newborn baby, use all medications to control your infection during pregnancy. Your name may be listed on an antiviral pregnancy registry.

Women with HIV should not breastfeed. The virus can pass to your baby in your breast milk.

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

Get your prescription refilled before you run out of medicine completely.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Drinking alcohol may increase your risk of liver damage.

Using tenofovir will not prevent your disease from spreading. Do not have unprotected sex or share razors or toothbrushes. Ask your doctor how to prevent HIV transmission during sex. Sharing drug or medicine needles is never safe.

Get emergency medical help if you have signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Mild symptoms of lactic acidosis may worsen over time, and this condition can be fatal. Get emergency medical help if you have: unusual muscle pain, trouble breathing, stomach pain, vomiting, fast/slow or irregular heartbeats, dizziness, feeling cold, or feeling very weak or tired.

Tenofovir may cause serious side effects. Call your doctor at once if you have:

• sore throat, flu symptoms, easy bruising or unusual bleeding;

• kidney problems--little or no urination, painful or difficult urination, swelling in your feet or ankles, feeling tired or short of breath; or

• liver problems--swelling around your midsection, upper stomach pain, unusual tiredness, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes).

Tenofovir can affect your immune system (even weeks or months after you've used tenofovir). Tell your doctor if you have:

• signs of a new infection--fever, night sweats, swollen glands, cold sores, cough, wheezing, diarrhea, weight loss;

• trouble speaking or swallowing, problems with balance or eye movement, weakness or prickly feeling; or

• swelling in your neck or throat (enlarged thyroid), menstrual changes, impotence.

Common side effects of tenofovir may include:

• stomach pain, nausea, vomiting, diarrhea;

• fever, pain;

• weakness, dizziness;

• headache;

• depressed mood;

• itching, rash; or

• sleep problems (insomnia).

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Sometimes it is not safe to use certain medications at the same time. Some drugs can affect your blood levels of other drugs you take, which may increase side effects or make the medications less effective.

Tenofovir can harm your kidneys, especially if you also use certain medicines for infections, cancer, osteoporosis, organ transplant rejection, high blood pressure, or pain or arthritis (including Advil, Motrin, and Aleve).

Many drugs can affect tenofovir. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed here. Tell your doctor about all other medicines you use.