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tenofovir

General

Pronunciation:
te-noe-fo-veer


Trade Name(s)

  • Viread

Pregnancy Category
Category B

Ther. Class.
antiretrovirals

Pharm. Class.
nucleoside reverse transcriptase inhibitors

Indications

  • HIV infection (with other antiretrovirals).
  • Chronic hepatitis B.

Action

Active drug (tenofovir) is phosphorylated intracellularly; tenofovir diphosphate inhibits HIV reverse transcriptase resulting in disruption of DNA synthesis.

Therapeutic Effect(s):

  • Slowed progression of HIV infection and decreased occurrence of sequelae.
  • Increased CD4 cell count and decreased viral load.
  • Decreased progression/sequelae of chronic hepatitis B infection.

Pharmacokinetics

Absorption: Tenofovir disoproxil fumarate is a prodrug, which is split into tenofovir, the active component.

Distribution: Absorption is enhanced by food.

Metabolism and Excretion: 70–80% excreted unchanged in urine by glomerular filtration and active tubular secretion.

Half-life: Unknown.

TIME/ACTION PROFILE (blood levels)

ROUTEONSETPEAKDURATION
POunknown2 hr*24 hr
*When taken with food.

Contraindication/Precautions

Contraindicated in:

  • Hypersensitivity;
  • Concurrent use of antiretroviral combination products containing tenofovir
  • Concurrent or recent use of NSAIDs (↑ risk of acute renal failure)
  • Lactation:HIV-infected women should not breast feed.

Use Cautiously in:

  • Co-infection with HIV and chronic hepatitis B;
  • Obesity, women, prolonged nucleoside exposure (may be risk factors for lactic acidosis/hepatomegaly);
  • Renal impairment (↑ dosing interval if CCr <50 mL/min);
  • History of pathologic bone fractures or at risk for osteopenia;
  • OB: Has been used safely;
  • Pedi: Children <2 yr (safety not established).

Adverse Reactions/Side Effects

CNS: depression, headache, weakness

Endo: fat redistibution

GI: HEPATOMEGALY, (with steatosis), diarrhea, nausea, abdominal pain, anorexia, vomiting, flatulence

GU: ACUTE RENAL FAILURE/FANCONI SYNDROME, proximal renal tubulopathy, renal impairment

F and E: LACTIC ACIDOSIS, hypophosphatemia

Derm: rash

MS: bone pain, ↓ bone mineral density, muscle pain, osteomalacia

Misc: immune reconstitution syndrome

* CAPITALS indicate life-threatening.
Underline indicate most frequent.

Interactions

Drug-Drug

  • May ↑ didanosine levels; ↓ didanosine dose.
  • Blood levels may be ↑ by cidofovir, acyclovir, ganciclovir, or valganciclovir.
  • Risk of renal toxicity ↑ by other nephrotoxic agents.
  • Combination therapy with atazanavir may lead to ↓ virologic response and possible resistance to atazanavir (small amounts of ritonavir may be added to boost blood levels); may also ↑ tenofovir levels.
  • Lopinavir/ritonavir may ↑ levels.
  • Concurrent use with adefovir for chronic hepatitis B infection should be avoided.
  • Concurrent use with NSAIDs may ↑ risk of acute renal failure

Route/Dosage

HIV

PO: (Adults and Children ≥12 yr and ≥35 kg): 300 mg once daily.

Renal Impairment
PO: (Adults ): CCr 30–49 mL/min– 300 mg every 48 hr; CCr 10–29 mL/min– 300 mg every 72–96 hr; Hemodialysis– 300 mg every 7 days following dialysis.

PO: (Children 2–11 yr and ≥17 kg): Tablets: ≥35 kg– 300 mg once daily; 28–34.9 kg– 250 mg once daily; 22–27.9 kg– 200 mg once daily; 17–21.9 kg– 150 mg once daily;.

PO: (Children 2–11 yr): Oral Powder: ≥35 kg– 7.5 scoops (300 mg) once daily; 34–34.9 kg– 7 scoops (280 mg) once daily; 32–33.9 kg– 6.5 scoops (260 mg) once daily; 29–31.9 kg– 6 scoops (240 mg) once daily; 27–28.9 kg– 5.5 scoops (220 mg) once daily; 24–26.9 kg– 5 scoops (200 mg) once daily; 22–23.9 kg– 4.5 scoops (180 mg) once daily; 19–21.9 kg– 4 scoops (160 mg) once daily; 17–18.9 kg– 3.5 scoops (140 mg) once daily; 14–16.9 kg– 3 scoops (120 mg) once daily; 12–13.9 kg– 2.5 scoops (100 mg) once daily; 10–11.9 kg– 2 scoops (80 mg) once daily;.

Chronic Hepatitis B

PO: (Adults and Children ≥12 yr and ≥35 kg): 300 mg once daily.

Renal Impairment
PO: (Adults ): CCr 30–49 mL/min– 300 mg every 48 hr; CCr 10–29 mL/min– 300 mg every 72–96 hr; Hemodialysis– 300 mg every 7 days following dialysis.

Availability

Tablets: 150 mg, 200 mg, 250 mg, 300 mg

Oral powder: 40 mg/scoop

In Combination with:emtricitabine (Truvada); emtricitabine and rilpivirine (Complera); efavirenz and emtricitabine (Atripla); elvitegravir, cobicistat, and emtricitabine (Stribild). See combination drugs.

Assessment

  • Monitor for change in severity of HIV symptoms and for symptoms of opportunistic infection before and during therapy.
  • Monitor bone mineral density in patients who have a history of pathologic bone fracture or are at risk for osteoporosis or bone loss.

Lab Test Considerations: Monitor viral load and CD4 count before and routinely during therapy to determine response.

  • Monitor liver function tests and hepatitis B virus levels throughout and following therapy. If therapy is discontinued, may cause severe exacerbation of hepatitis B. May cause ↑ AST, ALT, alkaline phosphatase, creatine kinase, amylase, and triglyceride concentrations. Lactic acidosis may occur with hepatic toxicity causing hepatic steatosis; may be fatal, especially in women.
  • Calculate creatinine clearance prior to and periodically during therapy and when clinically indicated. In patients at risk of renal dysfunction, assess creatinine clearance, serum phosphorus, urine glucose, and urine protein prior to and periodically during therapy.
  • Monitor serum phosphate periodically during therapy in patients at risk for renal impairment. May cause hypophosphatemia in patients with renal impairment.
  • May cause hyperglycemia and glucosuria.

Potential Diagnoses

Implementation

  • When tenofovir is administered concomitantly with didanosine, administer tenofovir 2 hr before or 1 hr after didanosine.
  • PO: Administer once daily with or without food.
    • Patients unable to swallow tablets can use oral powder. Using only dosing scoop, mix in soft food (applesauce, baby food, yogurt). Do not mix in liquid; powder floats to top even after stirring. Ingest entire mixture immediately to avoid bitter taste.

Patient/Family Teaching

  • Instruct patient on the importance of taking tenofovir as directed, even if feeling better. Do not take more than prescribed amount and do not stop taking without consulting health care professional. Discontinuing therapy may lead to severe exacerbations. Take missed doses as soon as remembered unless almost time for next dose; do not double doses. Caution patient not to share or trade this medication with others.
  • Inform patient that tenofovir may cause hyperglycemia. Advise patient to notify health care professional if increased thirst or hunger; unexplained weight loss; increased urination; fatigue; or dry, itchy skin occurs.
  • Instruct patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and consult health care professional before taking any new medications.
  • Caution patient to avoid crowds and persons with known infections.
  • Inform patient that tenofovir does not cure AIDS and does not reduce the risk of transmission of HIV to others through sexual contact or blood contamination. Caution patient to use a condom and avoid sharing needles or donating blood to prevent spreading HIV to others.
  • Advise patient to notify health care professional immediately if symptoms of lactic acidosis (nausea, vomiting, unusual or unexpected stomach discomfort, and weakness) or signs of Immune Reconstitution Syndrome (signs and symptoms of an infection) occur.
  • Inform patient that changes in body fat distribution (increased fat in upper back and neck, breast, and trunk, and loss of fat from legs, arms, and face) may occur, but may not be related to drug therapy.
  • Rep: Advise patient taking oral contraceptives to use a nonhormonal method of birth control during tenofovir therapy. If pregnancy is suspected notify health care professional promptly. Encourage pregnant women to enroll in the Antiretroviral Pregnancy Registry by calling 1–800–258–4263. Advise female patient to avoid breast feeding during therapy.
  • Emphasize the importance of regular exams to monitor for side effects.

Evaluation/Desired Outcomes

  • Decreased incidence of opportunistic infection and slowed progression of HIV infection.
  • Slowed progression of chronic hepatitis B infection.
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Citation

Quiring, Courtney, et al. "Tenofovir." Davis's Drug Guide, 16th ed., F.A. Davis Company, 2019. Medicine Central, im.unboundmedicine.com/medicine/view/Davis-Drug-Guide/110536/all/tenofovir.
Quiring C, Sanoski CA, Vallerand AH. Tenofovir. Davis's Drug Guide. 16th ed. F.A. Davis Company; 2019. https://im.unboundmedicine.com/medicine/view/Davis-Drug-Guide/110536/all/tenofovir. Accessed April 24, 2019.
Quiring, C., Sanoski, C. A., & Vallerand, A. H. (2019). Tenofovir. In Davis's Drug Guide. Available from https://im.unboundmedicine.com/medicine/view/Davis-Drug-Guide/110536/all/tenofovir
Quiring C, Sanoski CA, Vallerand AH. Tenofovir [Internet]. In: Davis's Drug Guide. F.A. Davis Company; 2019. [cited 2019 April 24]. Available from: https://im.unboundmedicine.com/medicine/view/Davis-Drug-Guide/110536/all/tenofovir.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - tenofovir ID - 110536 A1 - Quiring,Courtney, AU - Sanoski,Cynthia A, AU - Vallerand,April Hazard, BT - Davis's Drug Guide UR - https://im.unboundmedicine.com/medicine/view/Davis-Drug-Guide/110536/all/tenofovir PB - F.A. Davis Company ET - 16 DB - Medicine Central DP - Unbound Medicine ER -