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Pharmacologic class: Guanosine nucleoside analogue

Therapeutic class: Antiviral

Pregnancy risk category C

FDA Box Warning

• Drug may cause lactic acidosis and severe hepatomegaly with steatosis (including fatal cases) when used alone or in combination with antiretrovirals.

• Severe acute hepatitis B exacerbations have occurred in patients who discontinued anti-hepatitis B therapy, including entecavir. Monitor hepatic function for at least several months after discontinuation. If appropriate, initiate anti-hepatitis B therapy.

• When used to treat chronic hepatitis B, drug may cause human immunodeficiency virus (HIV) resistance to HIV nucleoside reverse transcriptase inhibitors in patients with untreated HIV infection. Therapy isn't recommended for HIV/hepatitis B virus (HBV) co-infected patients except those also receiving highly active antiretroviral therapy.


Competes with natural substrate deoxyguanosine triphosphate to inhibit HBV polymerase (reverse transcriptase)


Oral solution: 0.05 mg/ml

Tablets: 0.5 mg, 1 mg

Indications and dosages

Chronic HBV infection with evidence of active viral replication and either persistent serum transaminase elevations or histologically active disease

Adolescents and adults ages 16 and older: In nucleoside-treatment-naïve patients with compensated liver disease, 0.5 mg P. O. once daily. In patients with a history of hepatitis B viremia while receiving lamivudine or known lamivudine or telbivudine resistance mutations rtM204I/V with or without rtL180M, rtL80I/V, or rtV173L, or patients with decompensated liver disease, 1 mg P.O. once daily.

Dosage adjustment

• Creatinine clearance below 50 ml/minute


• Hypersensitivity to drug or its components


Use cautiously in:

• liver transplant recipients who are receiving or have received immunosuppressants that may affect renal function

• elderly patients

• pregnant or breastfeeding patients

• children younger than age 16.


• Administer at least 2 hours before or after a meal.

Adverse reactions

CNS: headache, dizziness, fatigue

GI: nausea, diarrhea, dyspepsia, increased GI enzymes

Hematologic: hematuria

Hepatic: HBV exacerbation, severe hepatomegaly

Metabolic: glycosuria,lactic acidosis


Drug-drug. Drugs that reduce renal function or compete for active tubular secretion: increased blood levels of either drug

Drug-diagnostic tests. Alanine aminotransferase, amylase, aspartate aminotransferase, lipase, glucose, serum creatinine, total bilirubin: increased

Patient monitoring

• Monitor renal function before and during therapy, especially in liver transplant recipients who are receiving or have received immunosuppressants that may affect renal function.

Monitor liver function closely for evidence of HBV exacerbation for at least several months after drug discontinuation.

Monitor for lactic acidosis (associated with nucleoside analogues).

Patient teaching

• Instruct patient to take drug on empty stomach (at least 2 hours before or after a meal).

Teach patient about signs and symptoms of lactic acidosis and importance of contacting prescriber if these occur.

Instruct patient to immediately report worsening symptoms, such as increased yellowing of skin or eyes, dark urine, or fatigue.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above.

McGraw-Hill Nurse's Drug Handbook, 7th Ed. Copyright © 2013 by The McGraw-Hill Companies, Inc. All rights reserved


(en-tek-aveer) ,


(trade name)


Therapeutic: antivirals
Pharmacologic: nucleoside analogues
Pregnancy Category: C


Chronic hepatitis B infection with evidence of active disease.


Phosphorylated intracellularly to active form which acts as an analogue of guanosine, interfering with viral DNA synthesis.

Therapeutic effects

Decreased hepatic damage due to chronic hepatitis B infection.


Absorption: Well absorbed following oral administration.
Distribution: Extensive tissue distribution.
Metabolism and Excretion: 62–73% excreted unchanged by kidneys.
Half-life: Plasma—128–149 hr; intracellular—15 hr.

Time/action profile (blood levels)

POrapid0.5–1 hr24 hr


Contraindicated in: Hypersensitivity; Lactation: Potential for serious adverse effects in infant.
Use Cautiously in: Renal impairment (dose reduction recommended if CCr <50 mL/min;Liver transplant recipients (careful monitoring of renal function recommended);Patients coinfected with HIV (unless receiving highly active antiretroviral therapy; at ↑ risk for resistance); Obstetric: Use only if clearly needed, considering benefits and risks; Pediatric: Safety not established in children <16 yr; Geriatric: ↑ risk of toxicity due to age-related ↓ in renal function.

Adverse Reactions/Side Effects

Central nervous system

  • dizziness
  • fatigue
  • headache


  • hepatomegaly (with steatosis)
  • dyspepsia
  • nausea

Fluid and Electrolyte

  • lactic acidosis (life-threatening)


  • alopecia
  • rash


Drug-Drug interaction

Concurrent use of drugs which may impair renal function may ↑ blood levels and risk of toxicity.


Oral (Adults and Children >16 yr) 0.5 mg once daily; history of lamivudine resistance—1 mg once daily.

Renal Impairment

Oral (Adults and Children >16 yr) CCr 30–50 mL/min—0.25 mg once daily, history of lamivudine resistance—0.5 mg once daily; CCr 10– <30 mL/min—0.15 mg once daily, history of lamivudine resistance—0.3 mg once daily; CCr <10 mL/min—0.05 mg once daily, history of lamivudine resistance—0.1 mg once daily.

Availability (generic available)

Tablets: 0.5 mg, 1 mg
Oral solution orange: 0.05 mg/mL

Nursing implications

Nursing assessment

  • Monitor signs of hepatitis (jaundice, fatigue, anorexia, pruritus) during and for several months following discontinuation of therapy. Exacerbations may occur when therapy is discontinued.
  • May cause lactic acidosis and severe hepatomegaly with steatosis. Monitor patient for signs (↑ serum lactate levels, elevated liver enzymes, liver enlargement on palpation). Suspend therapy if clinical or laboratory signs occur.
  • Lab Test Considerations: Monitor liver function closely during and for several months following discontinuation of therapy. May cause ↑ AST, ALT, bilirubin, amylase, lipase, creatinine, and serum glucose. May cause ↓ serum albumin.

Potential Nursing Diagnoses

Risk for infection (Indications)
Noncompliance (Patient/Family Teaching)


  • Oral: Administer on an empty stomach at least 2 hr before or after a meal. Oral solution is ready to use and should not be diluted or mixed with water or any other liquid. Hold spoon in a vertical position and fill gradually to mark corresponding to the prescribed dose. Rinse dosing spoon with water after each daily dose. Store in outer carton at room temperature. After opening, solution can be used until expiration date on bottle.

Patient/Family Teaching

  • Instruct patient to read the Patient Information with each refill and to take entecavir as directed. Take missed doses as soon as possible unless almost time for next dose. Do not run out of entecavir; get more when supply runs low. Do not double doses. Emphasize the importance of compliance with full course of therapy, not taking more than the prescribed amount, and not discontinuing without consulting health care professional. Inform patient that hepatitis exacerbation may occur upon discontinuation of therapy. Caution patient not to share medication with others.
  • Inform patient that entecavir does not cure HBV disease, but may lower the amount of HBV in the body, lower the ability of HBV to multiply and infect new liver cells, and may improve the condition of the liver. Entecavir does not reduce the risk of transmission of HBV to others through sexual contact or blood contamination. Caution patient to use a condom during sexual contact and avoid sharing needles or donating blood to prevent spreading HBV to others.
  • Advise patient to notify health care professional promptly if signs of lactic acidosis (weakness or tiredness; unusual muscle pain; trouble breathing; stomach pain with nausea and vomiting; feeling cold, especially in arms or legs; dizziness, fast or irregular heartbeat) or hepatotoxicity (jaundice, dark urine, light-colored bowel movements, anorexia, nausea, lower stomach pain) occur.
  • May cause dizziness. Caution patient to avoid driving or other activities requiring alertness until response to medication is known.
  • Instruct patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and to consult with health care professional before taking other medications.
  • Discuss the possibility of hair loss with patient. Explore methods of coping.
  • Advise patient to notify health care professional if pregnancy is planned or suspected or if breast feeding.
  • Emphasize the importance of regular follow-up exams and blood tests to determine progress and monitor for side effects.

Evaluation/Desired Outcomes

  • Decreased hepatic damage due to chronic hepatitis B infection.
Drug Guide, © 2015 Farlex and Partners


A guanosine analogue antiviral drug with good activity against HEPATITIS B virus DNA polymerase.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
References in periodicals archive ?
Furthermore, we performed a review of literature to compile previously reported drug reactions related to entecavir.
An ANOVA test was conducted for comparison of the variables that fit a normal distribution in the 3 treatment groups (lamividune, entecavir, and tenofovir groups).
The patent and licensing status of entecavir and tenofovir, the two WHO-recommended HBV medications, influence medicine prices (7).
The number of studies applying the sequential nucleotide analogs (NUCs) to pegylated interferon (Peg-INF) strategy was limited, and the following two studies did not support previous result.[10] The current randomized controlled study investigated the treatment efficacy and adverse effects of sequential Peg-IFN treatment with short-term use of entecavir (ETV) for 12 weeks.
The researchers found that all low- and middle-income countries could legally procure generic entecavir and all but two could legally procure tenofovir in 2017.
for the manufacturing of entecavir and cilostazol, the company said.
Pharmaceutical company Breckenridge Pharmaceutical Inc reported on Tuesday the receipt of final approval from the US Food and Drug Administration for its Abbreviated New Drug Application for Entecavir tablets USP in 0.5mg and 1mg for the treatment of chronic hepatitis B virus infection.
In a randomized clinical study, the HBV reactivation rate was 6.6% with entecavir and 30% with lamivudine in HBsAg-positive patients receiving rituximab-containing chemotherapy for diffuse large B-cell lymphoma.
Furthermore, by posttreatment week 53, one of these patients developed bilirubinemia and symptomatic HBV infection (malaise, anorexia, sclera jaundice, and nausea), which resolved after treatment with entecavir.
The drug classes included nucleosides analogues including adenosine analogues (Adefovir and Tenofovir), guanosine analogues (Entecavir and Ribavirin), cytidine analogue (Lamivudine), immunostimulant (Cycloferon), and Interferon-like analogues (Interferon, Pegylated Interferon alpha-2a).
* Adults with immune-active disease should receive pegylated interferon (Pegasys[R]), entecavir (Baraclude[R]), or tenofovir disopoxil fumarate (Viread[R]) as initial therapy regardless of [HB.sub.e]Ag status (low quality/certainty of evidence; strong recommendation).