In the U.S.—

• Antiviral

Tenofovir ( te-NOE-fo-veer) is used, in combination with other medicines, in the treatment of the infection caused by the human immunodeficiency virus (HIV). HIV is the virus that causes acquired immunodeficiency syndrome (AIDS).

Tenofovir will not cure or prevent HIV infection or AIDS; however, it may help keep HIV from reproducing which may slow down the destruction of the immune system. This may help delay the development of problems usually related to AIDS or HIV disease. Tenofovir will not keep you from spreading HIV to other people. People who receive this medicine may continue to have other problems usually related to AIDS or HIV disease.

This medicine is available only with your doctor's prescription, in the following dosage form:

Oral
• Tablets (U.S.)

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For tenofovir, the following should be considered:

Allergies—Tell your doctor if you have ever had any unusual or allergic reaction to tenofovir. Also tell your health care professional if you are allergic to any other substances, such as foods, preservatives, or dyes.

Pregnancy—Tenofovir has not been studied in pregnant women. However, tenofovir has not been shown to cause birth defects or other problems in animal studies.

Breast-feeding—It is not known whether tenofovir passes into breast milk. However, because of the possibility that this medicine could cause unwanted effects in nursing babies and the risk of passing HIV on to the infant, breast-feeding is usually not recommended.

Children—Studies on this medicine have been done only in adult patients, and there is no specific information comparing use of tenofovir in children with use in other age groups.

Older adults—Many medicines have not been studied specifically in older people. Therefore, it may not be known whether they work exactly the same way they do in younger adults. Although there is no specific information comparing use of tenofovir in the elderly with use in other age groups, this medicine is not expected to cause different side effects or problems in older people than it does in younger adults.

Other medicines— Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking tenofovir, it is especially important that your health care professional know if you are taking the following:

• Atazanavir—Use of atazanavir and tenofovir may increase your risk for tenofovir side effects.

• Didanosine—Use of didanosine and tenofovir may increase your risk for didanosine side effects.

• Lopinavir and ritonavir—Use of this combination therapy with tenofovir may increase your risk for tenofovir side effects.

• Hepatitis B virus infection—May be worsened if tenofovir is discontinued.

• Kidney disease or
• Liver disease—May be worsened by tenofovir.

Take this medicine exactly as directed by your doctor. Do not take it more often, and do not take it for a longer time than your doctor ordered. Also, do not stop taking this medicine without checking with your doctor first.

This medicine may be taken with or without food.

This medicine works best when there is a constant amount in the blood. To help keep the amount constant, do not miss any doses.

Dosing—

The dose of tenofovir will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of tenofovir. If your dose is different, do not change it unless your doctor tells you to do so.

• For oral dosage form (tablets):
  • For HIV infection:
    • Adults—300 milligrams (mg) once a day with a meal. You may take this medicine less often if you have kidney problems.
    • Children—Use and dose must be determined by your doctor.

Missed dose—

If you miss a dose of this medicine, take it as soon as you remember. However, if it is almost time for the next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

Storage—

To store this medicine:

• Keep out of the reach of children.
• Do not store in the bathroom, near the kitchen sink, or in other damp places. Heat or moisture may cause the medicine to break down.
• Do not keep outdated medicine or medicine no longer needed. Ask your health care professional how you should dispose of any medicine you do not use. Be sure that any discarded medicine is out of the reach of children.

It is very important that your doctor check you at regular visits to make sure this medicine is working properly and to check for unwanted effects.

This medicine may cause serious problems with your liver or cause too much acid in your blood. If untreated, it can lead to severe low blood pressure and even death. Check with your doctor immediately if you notice abdominal discomfort; decreased appetite; diarrhea; fast, shallow breathing; general feeling of discomfort; muscle pain or cramping; nausea; shortness of breath; sleepiness; or unusual tiredness or weakness.

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

• Rare
  • Abdominal discomfort;  decreased appetite ;  diarrhea;  fast, shallow breathing;  general feeling of discomfort;  muscle pain or cramping;  nausea;  shortness of breath;  sleepiness;  unusual tiredness or weakness 
  
  

• Incidence not known
  • Agitation;  bloating;  bloody or cloudy urine;  bone pain;  chills;  coma;  confusion ;  constipation;  convulsions or seizures;  darkened urine;  decreased frequency or amount of urine;  depression ;  difficult or painful urination;  dizziness;  fast heartbeat;  fever;  headache;  hostility ;  increased blood pressure;  increased thirst;  indigestion;  irritability;  lethargy;  loss of appetite;  muscle twitching;  pains in stomach, side, or abdomen, possibly radiating to the back;  stupor;  swelling of face, fingers, lower legs;  trouble breathing;  vomiting;  weight gain;  yellow eyes or skin 
  
  

Other side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any of the following side effects continue or are bothersome.

• More common
  • Lack or loss of strength 
  
  

• Less common
  • Passing of gas;  weight loss 
  
  

Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.

Once a medicine has been approved for marketing for a certain use, experience may show that it is also useful for other medical problems. Although this use is not included in product labeling, tenofovir is used in certain patients with the following medical condition:

• Human immunodeficiency virus (HIV) infection in combination with hepatitis B virus (HBV) infection

Other than the above information, there is no additional information relating to proper use, precautions, or side effects for this use.