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 Hepsera. If you are concerned about side effects, discuss the risks and benefits of Hepsera with your doctor.

The following side effects have been reported by at least 1% of people taking Hepsera. 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
• gas
• headache
• indigestion
• nausea
• skin rash or itching
• stomach pain
• tiredness
• weakness

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

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

• bone pain and softening of the bone
• muscle pain or weakness
• signs of kidney problems (e.g., change in the amount or colour of urine, increased urination at night, blood in the urine, swelling in the feet or legs)
• symptoms of liver problems (e.g., yellowing of the skin or whites of eyes, dark urine, pale stools, loss of appetite, nausea, lower stomach pain)

Seek immediate medical attention if any of the following occur:

• signs of pancreatitis (e.g., abdominal pain on the upper left side, back pain, nausea, Fever, chills, rapid heartbeat, swollen abdomen)
• symptoms of lactic acidosis (e.g., unusual weakness or tiredness, unusual muscle pain, stomach pain with nausea and vomiting, feeling cold especially in the arms and legs, dizziness or lightheadedness, fast or irregular heartbeat)

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 Hepsera.

Each white, flat-faced tablet, debossed with "10" and "GILEAD" on one side and the stylized figure of a liver on the other side, contains adefovir dipivoxil 10 mg. Nonmedicinal ingredients:croscarmellose sodium, lactose monohydrate, magnesium stearate, pregelatinized starch, and talc.

Adefovir should not be taken by anyone who is allergic to adefovir or to any of the ingredients of the medication.

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

• Cabozantinib
• Cladribine
• Orlistat
• tenofovir
• Teriflunomide
• Tolvaptan

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 Hepsera. 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.

Before you begin taking 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 take Hepsera.

Hepatitis B transmission: The hepatitis B infection can still be transmitted to other people through blood contamination or sexual contact while you are taking Hepsera. Continue to take appropriate precautions to prevent the transmission of hepatitis B throughout your treatment with adefovir.

HIV and hepatitis B co-infections: If you get or have HIV infection and are not taking medication to treat HIV, adefovir 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 adefovir and whenever there is a risk of HIV exposure during treatment. Adefovir should not be taken in combination with certain other medications used to treat HIV infection.

Kidney problems: Hepsera may cause kidney problems, especially for people who have or are at risk of developing reduced kidney function (e.g., taking other medications that can cause kidney problems, high blood pressure, Diabetes). Your doctor will monitor your kidney function while you are taking Hepsera. If you have reduced kidney function, you may require longer periods of time between doses.

Lactic acidosis and enlarged liver: Adefovir can cause a condition called lactic acidosis (buildup of lactic acid) together with an enlarged liver. If you experience any of the following symptoms, call your doctor immediately:

• abdominal pain with nausea and vomiting
• dark yellow or brown urine
• difficulty breathing
• dizziness or lightheadedness
• fast or irregular heartbeat
• feeling cold, especially in the arms and legs
• loss of appetite
• pale stools
• unusual muscle pain
• unusual tiredness or weakness
• yellowing of the skin or eyes

Your doctor will periodically monitor you and perform laboratory tests to check your liver function.

Stopping the medication: People with hepatitis may experience a worsening of their condition usually within 12 weeks of stopping Hepsera. If you and your doctor decide that you should stop taking adefovir, you will need to have regular blood tests to check liver function and hepatitis B virus levels.

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

Breast-feeding: It is not known if adefovir passes into breast milk. Breast-feeding is not recommended while taking Hepsera.

Children: The safety and effectiveness of Hepsera have not been established for children.