Adefovir is an antiviral medication. It works by preventing viral cells from multiplying in the body and infecting new liver cells.

Adefovir is used to treat chronic hepatitis B in adults. This medicine will not cure hepatitis.

Adefovir may also be used for purposes other than those listed in this medication guide.

Take this medication exactly as it was prescribed for you. Do not take the medication in larger amounts, or take it for longer than recommended by your doctor. Follow the directions on your prescription label.

Take adefovir with a full glass of water.

Adefovir may be taken with or without food.

It is important to use adefovir regularly to get the most benefit. Get your prescription refilled before you run out of medicine completely.

To be sure this medication is not causing harmful effects, your blood will need to be tested on a regular basis. Your kidney or liver function may also need to be tested.

Your liver symptoms may become severe after you stop taking adefovir, even months after stopping. Your doctor may want to check your liver function on a regular basis for several months after you stop using adefovir. Do not miss any scheduled visits to your doctor.

If your condition worsens after you stop taking adefovir, your doctor may recommend that you restart this medication or another treatment for hepatitis B.

While taking adefovir, you should remain under the care of a doctor.

Store adefovir at room temperature away from moisture and heat.

Before taking adefovir, tell your doctor if you are using any of the following drugs:

• amphotericin B (Fungizone, AmBisome, Amphotec, Abelcet);

• pentamidine (Nebupent, Pentam);

• tacrolimus (Prograf);

• antibiotics such as capreomycin (Capastat), rifampin (Rifadin, Rimactane, Rifater), vancomycin (Vancocin, Vancoled);

• antiviral medicines such as acyclovir (Zovirax), cidofovir (Vistide), or foscarnet (Foscavir);

• cancer medicine such as aldesleukin (Proleukin), carmustine (BiCNU, Gliadel), cisplatin (Platinol), ifosfamide (Ifex), oxaliplatin (Eloxatin), plicamycin (Mithracin), streptozocin (Zanosar), or tretinoin (Vesanoid); or

• HIV medicines such as abacavir (Ziagen), didanosine (Videx), efavirenz (Sustiva), emtricitabine (Emtriva), lamivudine (Epivir), stavudine (Zerit), tenofovir (Viread), zalcitabine (Hivid), zidovudine (Retrovir), or combinations such as Atripla, Combivir, Epzicom, Trizivir, or Truvada.

If you are using any of these drugs, you may not be able to use adefovir, or you may need dosage adjustments or special tests during treatment.

There may be other drugs not listed that can affect adefovir. Tell your doctor about all the prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor.

Avoid having unprotected sex or sharing needles, razors, or toothbrushes. Taking this medication will not prevent you from passing hepatitis B to other people. Talk with your doctor about safe methods of preventing hepatitis transmission during sex, such as using a condom and spermicide. Sharing drug or medicine needles is never safe, even for a healthy person.

Seek emergency medical attention if you think you have used too much of this medicine.

Symptoms of an adefovir overdose may include nausea, vomiting, diarrhea, and other stomach problems.

Take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and take the medicine at your next regularly scheduled time. Do not take extra medicine to make up the missed dose.

This medication may cause lactic acidosis (the build up of lactic acid in the body). Lactic acidosis can start slowly and gradually get worse. Symptoms include unusual muscle pain and weakness, trouble breathing, fast or uneven heart rate, nausea, vomiting, stomach pain, and numbness or cold feeling in your arms or legs. Contact your doctor at once if you have any of these symptoms, even if they are only mild. Early signs of lactic acidosis generally get worse over time and this condition can be fatal.

Adefovir can also cause serious kidney problems, especially if you have kidney disease or take certain medications.

Your liver symptoms may become severe after you stop taking adefovir, even months after stopping. Your doctor may want to check your liver function on a regular basis for several months after you stop taking adefovir. Do not miss any scheduled appointments.

Avoid having unprotected sex or sharing needles, razors, or toothbrushes. Taking adefovir will not prevent you from passing hepatitis B to other people. Talk with your doctor about safe methods of preventing hepatitis transmission during sex, such as using a condom and spermicide. Sharing drug or medicine needles is never safe, even for a healthy person.

Tell your doctor if you have been exposed to HIV, or if you have untreated HIV or AIDS. Taking medicines to treat chronic hepatitis B can cause HIV infection to become resistant to the standard HIV and AIDS medications. You may need to be tested for HIV before you start taking adefovir.

Do not use this medication if you are allergic to adefovir.

Before taking adefovir, tell your doctor if you are allergic to any drugs, or if you have kidney or liver disease.

Tell your doctor if you have been exposed to HIV, or if you have untreated HIV or AIDS. Taking medicines to treat chronic hepatitis B can cause HIV infection to become resistant to the standard HIV and AIDS medications. You may need to be tested for HIV before you start taking adefovir.

This medication may cause lactic acidosis (the build up of lactic acid in the body). Lactic acidosis can start slowly and gradually get worse. Symptoms include unusual muscle pain and weakness, trouble breathing, fast or uneven heart rate, nausea, vomiting, stomach pain, and numbness or cold feeling in your arms or legs. Contact your doctor at once if you have any of these symptoms, even if they are only mild. Early signs of lactic acidosis generally get worse over time and this condition can be fatal.

FDA pregnancy category C. This medication may be harmful to an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant during treatment.

Your name may need to be listed on an antiviral pregnancy registry if you are pregnant while using this medication. The purpose of this registry is to track the outcome of the pregnancy and delivery to evaluate whether adefovir had any effect on the baby.

It is not known whether adefovir passes into breast milk or if it could harm a nursing baby. Do not use this medication without telling your doctor if you are breast-feeding a baby.

Your pharmacist has information about adefovir written for health professionals that you may read.

Adefovir is available with a prescription under then brand name Hepsera. Other brand or generic formulations may also be available. Ask your pharmacist any questions you have about this medication, especially if it is new to you.

• Hepsera 10 mg–white tablets