In the U.S.—

• Antiviral, systemic

Adefovir (a-DEF-oh-veer) is used to treat adults with chronic infections of active hepatitis B. Adefovir is not a cure for the hepatitis B virus, but it may lower the amount of hepatitis B virus in your body. It may also lower the ability of the virus to multiply in your body.

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

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 adefovir, the following should be considered:

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

Pregnancy—Adefovir has not been studied in pregnant women. However, studies in animals have shown that adefovir may cause birth defects or other problems. Before taking this medicine, make sure your doctor knows if you are pregnant or if you may become pregnant.

Breast-feeding—It is not known whether adefovir passes into breast milk. However, it should not be used by women who are breast-feeding because it may cause unwanted effects in nursing babies.

Children—Studies on adefovir have been done only in adult patients, and there is no specific information comparing the use of adefovir 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. Older patients should use this medicine with caution. Elderly people can be especially sensitive to the effects of medicines.

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 adefovir, it is especially important that your doctor and pharmacist know if you are taking any of the following:

• Nephrotoxic medicines (medicines that can be harmful to your kidneys), such as:
• Aminoglycosides (medicines used to treat infection) or
• Cyclosporine (e.g., Sandimmune or Neoral) or
• Non-steroidal anti-inflammatory medicines (medicines used to treat pain and inflammation) or
• Tacrolimus (e.g. Prograf) or
• Vancomycin (medicine used to treat severe infections)—Using these medicines with adefovir may cause you to have a higher chance of having problems with your kidneys.

• Nucleoside analog medicines (other antiviral medicines), such as:
• Abacavir (e.g. Ziagen) or
• Abacavir, Lamivudine, and Zidovudine (e.g. Trizivir) or
• Didanosine (e.g. Videx) or
• Lamivudine (e.g. Epivir) or
• Lamivudine and Zidovudine (e.g. Combivir) or
• Stavudine (e.g. Zerit) or
• Tenofovir (e.g. Viread) or
• Zalcitabine (e.g. Hivid) or
• Zidovudine (e.g. Retrovir)—Using these medicines with adefovir may cause you to have a higher chance of having problems with your liver or developing lactic acidosis.

• Human immunodeficiency virus (HIV)—It is important to talk to your doctor about the HIV virus before starting this medicine. Adefovir can make this condition worse.

• Kidney problems—Adefovir can cause kidney problems and your doctor may want to change your dose.

Dosing—

The dose of adefovir 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 adefovir. If your dose is different, do not change it unless your doctor tells you to do so.

• For oral dosage form (tablets):
  • For treatment of hepatitis B infection:
    • Adults: 10 milligrams (mg) once daily. May take with or without food.
    • 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 possible. However, if it is almost time for your 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.
• Keep the medicine from freezing. Do not refrigerate.
• 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 your progress and kidney function at regular visits. This will allow your doctor to see if the medicine is working properly.

Notify your doctor immediately if you think that you may be pregnant or plan to become pregnant. Certain medications may cause birth defects or other problems in the baby if taken during pregnancy.

Notify your doctor immediately if there is a chance you were exposed to HIV.

Be sure to follow up with your doctor after you stop this medicine so that your doctor can watch your liver function

Be sure that you notify your doctor immediately or get immediate medical attention if you notice abdominal discomfort or cramping, diarrhea, decreased appetite, discomfort, muscle cramping or pain, or unusual tiredness or weakness. These may be symptoms of a serious condition called lactic acidosis.

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:

• More common
  • Blood in your urine 
  
  

• Less Common
  • Sugar in your urine 
  
  

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
  • Abdominal pain;  headache;  lack or loss of strength 
  
  

• Less common
  • Acid or sour stomach;  belching;  bloated or full feeling;  diarrhea;  excess air or gas in stomach or intestines;  heartburn or indigestion;  nausea;  passing gas;  stomach discomfort, upset, or pain 
  
  

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