Use the search bar to find a specific medication or choose the first letter in the sidebar on the right.


Generic Name

entecavir (en TEH cuh veer)


Trade Name



What is entecavir?

Entecavir is an antiretroviral agent which works to injure a virus and fight infection.


What is it used for?

It is used in the treatment of the hepatitis B infection in adults.  It works by preventing viral cells from multiplying in the body and infecting new liver cells.  This medication will not sure hepatitis.


How do I take it?

Follow your physician’s instructions carefully. Entecavir can be either administered as an orange-flavored oral solution of 0.5 mg/ml or as a 0.5 mg tablet.  Use the calibrated oral dosing syringe provided with the oral solution.  Swallow the pill or capsule whole and do not break, crush or chew.  Keep all medications away from children.  Never share your medications with anyone else.


What do I do for a missed dose?

If you miss a dose of this medicine, take it as soon as possible. If it is almost time for your next dose, skip the missed dose and return to your regular schedule. Do not take a double dose of this medication.


Are there interactions with food or beverages?

The drug should be administered on an empty stomach (2 hours before or after a meal).  Do not dilute or mix oral solution with water or other beverages.  Food will delay absorption and reduce effectiveness of this medication.


Are there interactions with other drugs?

An interaction generally means that one drug may increase or decrease the effect of another drug. Interactions with this drug may occur with ganciclovir (Cytovene), valganciclovir (Valcyte) and ribavirin (Ripashere, RibaPak).


Is there a problem if I have another disorder or disease?

It is not advisable to take this drug if you are at a high risk for advanced liver damage or renal dysfunction.  This drug can cause worsening liver and kidney function.  If you have an unrecognized or untreated HIV infection, it is important to determine your HIV status before initiating treatment, since entecavir can cause of the development of HIV resistence.


What about allergies?

People who have known allergies or asthma may be at an increased risk for a reaction from any new medication. The physician should always know a patient’s allergy history. Signs of an allergic reaction are rash, hives, swelling and difficulty breathing. Of course, a person should not take entecavir if there has been a previous reaction to this or a similar drug.


What if I’m pregnant, considering pregnancy or breast-feeding?

In animal studies, entecavir had adverse effects on pregnancy, yet there are no adequate human studies of pregnant women taking entecavir.  This medication should be used during pregnancy only when clearly needed.  It is not advised to breast-feed while taking medication, since it is unknown if entecavir is excreted in breast milk.


What are the effects on sexual function?

There are no known effects of entecavir on sexual function.


Are there other precautions?

This medication may cause HIV resistance in chronic hepatitis B patients with unrecognized or untreated HIV infection.  Additionally, 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 and 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 may eventually lead to fatality.


How long is it safe to take entecavir?

A period of a few weeks is usually necessary to determine the drug’s effectiveness.  Long-term use of months to years is generally necessary and safe but does require a physician’s supervision and periodic evaluation.


How about side effects?

Adverse reactions can occur with any drug, even over-the-counter medications. Some of these are mild such as a stomach upset, which may be avoided by taking the medication with food. Minor reactions may go away on their own but, if they persist, contact the physician. For major reactions, the patient should contact the physician immediately.

For acetaminophen, the following are the observed side effects:


  • headache
  • nausea or vomiting
  • diarrhea
  • rash
  • lethargy
  • difficulty breathing


  • worsening kidney infection
  • worsening of hepatitis if medication is stopped


A physician’s comment…

This medication is not a cure for Hepatitis B, nor will it reduce the potential of transmission.  It is often used in conjunction with adefovir, another antiretroviral agent, to reduce viral DNA production.  Do not discontinue using this medication unless instructed by your physician.  Additional monitoring is required after the discontinuation to ensure that the disease does not recur.  Promptly report any new symptoms that occur during or after treatment to your doctor.