Tenofovir belongs to the family of medications called antiretrovirals. It is used with other antiretroviral medications to treat the infection caused by the human immunodeficiency virus (HIV). HIV is the virus responsible for acquired immune deficiency syndrome (AIDS). HIV infection destroys CD4 (T) cells, which are important to the immune system. The immune system helps fight infections.

Tenofovir is one of a type of antiretroviral medications called nucleoside reverse transcriptase inhibitors (NRTIs). Reverse transcriptase is a part of HIV required to infect cells and make more virus. Tenofovir prevents reverse transcriptase from working properly, thus lowering the amount of HIV in the blood. Tenofovir does not cure AIDS, but it may help to slow down the progression of the disease.

Tenofovir may also be used to treat chronic hepatitis B. It prevents the enzymes needed for the hepatitis B virus to reproduce from working properly. Tenofovir may help lower the amount of hepatitis B virus in the body by decreasing the ability of the virus to multiply and infect new liver cells.

Tenofovir does not prevent HIV or hepatitis B from being spread to others through sexual contact or blood contamination.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

For the treatment of HIV or chronic hepatitis B in adults, the recommended dose of tenofovir is 300 mg once daily with or without food. You may require a lower dose of tenofovir if you have severely impaired kidney function.

For the treatment of HIV in adolescent patients (over 12 years of age) and with a body weight of more than 35 kg, the recommended dose of tenofovir is 300 mg once daily with or without food.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important that this medication be taken exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature and keep it out of the reach of children.

Each blue, almond-shaped, biconvex film-coated tablet, debossed with "T" on one side and "300" on the other side, contains 300 mg of tenofovir disoproxil fumarate, which is equivalent to 245 mg of tenofovir disoproxil. Nonmedicinal ingredients:  lactose monohydrate, cellulose microcrystalline, croscarmellose sodium, starch pregelatinised (Starch 1500), magnesium stearate; coating: hypromellose, lactose monohydrate, titanium dioxide, lake pigment FD&C Blue No. 2, and triacetin.

Do not take tenofovir if you:

• are allergic to tenofovir or any ingredients of the medication
• are already taking another medication that contains tenofovir (e.g., emtricitabine - tenofovir, efavirenz - emtricitabine - tenofovir)

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• diarrhea
• dizziness
• gas (flatulence)
• headache
• muscle pain
• muscle weakness
• nausea
• rash
• stomach pain
• vomiting

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• bone pain or fractures
• signs of liver problems, such as:
• dark urine
• diarrhea
• loss of appetite
• nausea
• pale stools
• vomiting
• weight loss
• yellowing of the skin or whites of the eyes
• signs of kidney problems, such as:
• increased or decreased urination
• increased thirst
• swelling of the feet or legs
• signs of infection
• fever or chills
• severe diarrhea
• shortness of breath
• prolonged dizziness
• headache
• stiff neck
• weight loss
• listlessness

Stop taking the medication and seek immediate medical attention if any of the following occur:

• severe allergic reaction, such as:
• hives
• shortness of breath
• swelling of the face or throat
• signs of lactic acidosis, such as:
• abdominal pain
• dizziness
• feeling cold, especially in the arms and legs
• increased breathing rate
• nausea
• rapid heart rate
• unusual tiredness
• vomiting
• signs of pancreatitis, such as:
• abdominal pain on the upper left side
• back pain
• chills
• fever
• nausea
• rapid heartbeat
• swollen abdomen

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Bone health: Tenofovir may reduce bone mineral density and should not be taken by anyone who is at risk for bone problems. If you have osteoporosis, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. If you experience bone pain or a bone fracture while taking this medication, contact your doctor. Your doctor may do tests to monitor the effect of tenofovir on your bones.

Cholesterol: Tenofovir can cause increased levels of lipids in the bloodstream. If you are at risk of developing high cholesterol or you have high cholesterol levels before starting this medication, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Diabetes: This medication may cause an increase in blood sugar levels (may cause a loss of blood glucose control) and glucose tolerance may change. People with diabetes may find it necessary to monitor their blood sugar more frequently while using this medication.

HIV and hepatitis B co-infections: If you are taking tenofovir for hepatitis B infection and you get or have HIV infection and are not taking medication to treat HIV, tenofovir may increase the chance that your HIV infection will not respond to usual treatment. Therefore, it is important to be tested for HIV before starting treatment with tenofovir and whenever there is a risk of HIV exposure during treatment.

Immune reconstitution inflammatory syndrome: When you start taking tenofovir, your immune system may get stronger and start to fight other infections that have been hidden in your body (e.g., pneumonia, herpes, or tuberculosis). Contact your doctor if you develop any new symptoms after starting tenofovir. Report any signs of infection such as fever, chills, shortness of breath, cough, or rapid weight loss to your doctor immediately.

Kidney function: Kidney disease or reduced kidney function may cause this medication to build up in the body, causing increased side effects. If you have kidney disease or reduced kidney function, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. Tenofovir can cause kidney problems, including severe kidney damage and kidney failure. Your doctor may monitor your kidney function with blood tests while you are taking this medication. Additional tests may be needed if you have a history of kidney problems or if you need to take another medication that can cause kidney problems. Your doctor may also need to change the dosing schedule of this medication if you have existing kidney problems.

Lactic acidosis and enlarged liver: This medication can cause a rare but serious condition called lactic acidosis (buildup of lactic acid), together with an enlarged fatty liver. Your doctor will periodically monitor you and perform laboratory tests to check your liver function. If you notice any symptoms of this condition such as nausea, vomiting, stomach pain, weakness, tiredness, feeling cold, dizziness, lightheadedness, or irregular heartbeat, seek immediate medical attention.

Liver: Tenofovir can cause liver problems. If you have liver disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. Your doctor may monitor your liver function with blood tests while you are taking tenofovir, especially if you have risk factors for liver problems. Report any signs of liver problems (e.g., nausea, vomiting, diarrhea, loss of appetite, weight loss, yellowing of the skin or whites of the eyes, dark urine, pale stools) to your doctor.

Pancreatitis: Tenofovir may cause inflammation of the pancreas (pancreatitis). If you have a history of, or are at risk for developing, pancreatitis, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. If you develop signs of pancreatitis (e.g., upper left abdominal pain, back pain, nausea, fever, chills, rapid heartbeat, swollen abdomen), contact your doctor.

Stopping the medication: When used to treat chronic hepatitis B, stopping tenofovir has been known to cause symptoms of liver inflammation to flare up and your hepatitis B infection could get worse. Take the medication exactly as prescribed by your doctor, and do not stop taking the medication without checking with your doctor first. If you and your doctor decide that you should stop taking tenofovir, you will need to have regular blood tests to check liver function and hepatitis B virus levels.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: It is not known if tenofovir passes into breast milk. Women who have HIV infection are cautioned against breast-feeding because of the risk of passing HIV to a baby who does not have the infection.

Children: For the treatment of HIV infection, the safety and effectiveness of this medication have not been established for children less than 12 years old. For the treatment of chronic hepatitis B infection, the safety and effectiveness of this medication have not been established for children less than 18 years old.

There may be an interaction between tenofovir and any of the following:

• acyclovir
• adefovir
• aminoglycoside antibiotics (e.g., amikacin, gentamicin, tobramycin)
• amiodarone
• "azole" antifungals (e.g., itraconazole, ketoconazole, voriconazole)
• carvedilol
• celecoxib
• cladribine
• cobicistat
• cyclosporine
• dronedarone
• elagolix
• eliglustat
• eltrombopag
• enzalutamide
• flibanserin
• ganciclovir
• hepatitis C antivirals (e.g., ledipasvir, velpatasvir, voxilaprevir)
• HIV protease inhibitors (e.g., atazanavir, indinavir, ritonavir, saquinavir, tipranavir)
• ivacaftor
• ledipasvir
• macrolide antibiotics (e.g., azithromycin, clarithromycin, erythromycin)
  medications that affect kidney function (e.g., ACE inhibitors such as enalapril, vancomycin, tobramycin)
• nonsteroidal anti-inflammatory medications (NSAIDs; e.g., ASA, diclofenac, indomethacin, ketorolac, naproxen)
• orlistat
• osimertinib
• paromomycin
• propafenone
• quinidine
• teriflunomide
• valacyclovir
• valganciclovir
• vemurafenib
• verapamil

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.