tenofovir disoproxil fumarate

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

Therapeutic effects:

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. Absorption enhanced by food.

Distribution: Minimally distributed to extravascular tissues.

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

Half-Life: Unknown.

Time/Action Profile ⬆ ⬇

(blood levels)

ROUTE	ONSET	PEAK	DURATION
PO	unknown	2 hr*	24 hr

*When taken with food.

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity;
Concurrent use of antiretroviral combination products containing tenofovir;
Concurrent or recent use of NSAIDs (↑ risk of acute renal failure);
Lactation: Breastfeeding not recommended in women with HIV.

Use Cautiously in:

Co-infection with HIV and chronic hepatitis B (hepatitis B may exacerbate following discontinuation);
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 and effectiveness not established).

Adv. Reactions/Side Effects ⬆ ⬇

Derm: rash

F and E: hypophosphatemia

GI: diarrhea, nausea, abdominal pain, anorexia, flatulence, LACTIC ACIDOSIS/HEPATOMEGALY WITH STEATOSIS, vomiting

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

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

Neuro: depression, headache, weakness

Misc: immune reconstitution syndrome

Interactions ⬆ ⬇

Drug-drug:

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, ledipasvir/sofosbuvir, sofosbuvir/velpatasvir, and sofosbuvir/velpatasvir/voxilaprevirmay ↑ 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 ⬆ ⬇

PO (Adults and Children ≥2 yr and ≥35 kg): 300 mg once daily.
PO (Children ≥2 yr and 17–34.9 kg):
Tablets:
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 yr and 10–34.9 kg):
Oral Powder:
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.

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 ⬆ ⬇

(Generic available)

Oral powder: 40 mg/scoop
Tablets: 150 mg; 200 mg; 250 mg; 300 mg
In combination with: efavirenz and emtricitabine (Atripla); efavirenz and lamivudine (Symfi); cobicistat, and emtricitabine (Stribild); emtricitabine (Truvada); emtricitabine and rilpivirine (Complera); lamivudine (Cimduo, Temixys). See Appendix [not included in this PDA edition].

Assessment ⬆ ⬇

Monitor for change in severity of HIV symptoms and for symptoms of opportunistic infection before and during therapy.
Monitor weight of pediatric patients periodically and adjust dose accordingly.
Assess for persistent or worsening bone pain, pain in extremities, fractures and/or muscular pain or weakness periodically during therapy. May be signs of proximal renal tubulopathy; evaluate renal function in patients at risk of renal dysfunction.
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:

Prior to starting therapy, test patients for HBV infection and HIV-1 infection. Tenofovir alone should not be used to treat patients with HIV-1 infection.
- Monitor viral load and CD4 count before and routinely during therapy to determine response.
- Monitor liver function tests and hepatitis B virus levels during 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.
- Assess serum creatinine, creatinine clearance, urine glucose, and urine protein prior to and periodically during therapy and when clinically indicated. In patients with chronic kidney disease, 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.

Implementation ⬆ ⬇

PO: Administer once daily with or without food.
- Patients unable to swallow tablets can use oral powder. Using only dosing scoop, mix in 2–4 oz of 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 may 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.
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.

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇

Action ⬆ ⬇