tenofovir alafenamide

Converted by hydrolysis to tenofovir and subsequently phosphorylated to the active metabolite, tenofovir diphosphate, which inhibits replication of HBV through incorporation into viral DNA by the HBV reverse transcriptase, resulting in disruption of DNA synthesis.

Therapeutic effects:

Decreased progression/sequelae of chronic HBV infection.

Pharmacokinetics ⬆ ⬇

Absorption: Tenofovir alafenamide is a prodrug, which is hydrolyzed into tenofovir; absorption ↑ by high-fat meals.

Distribution: Unknown.

Metabolism/Excretion: Tenofovir is phosphorylated to tenofovir diphosphate (active metabolite); 32% excreted in feces, <1% in urine.

Half-Life: 0.51 hr.

Time/Action Profile ⬆ ⬇

(plasma concentrations)

ROUTE	ONSET	PEAK	DURATION
PO	unknown	0.5 hr	24 hr

Contraind./Precautions ⬆ ⬇

Contraindicated in:

End-stage renal disease (CCr <15 mL/min) (not receiving hemodialysis);
Decompensated hepatic impairment.

Use Cautiously in:

Coinfection with HIV and chronic HBV;
Renal impairment or receiving nephrotoxic medications (↑ risk of renal impairment);
OB: Use during pregnancy only if potential maternal benefit justifies potential fetal risk;
Lactation: Use while breastfeeding only if potential maternal benefit justifies potential risk to infant;
Pedi: Children <6 yr (safety and effectiveness not established).

Adv. Reactions/Side Effects ⬆ ⬇

GI: ↑amylase, ↑liver enzymes, abdominal pain, LACTIC ACIDOSIS/HEPATOMEGALY WITH STEATOSIS, nausea

GU: ACUTE RENAL FAILURE/FANCONI SYNDROME, glycosuria

Metab: hyperlipidemia

MS: ↑CK, back pain

Neuro: fatigue, headache

Resp: cough

Interactions ⬆ ⬇

Drug-drug:

Nephrotoxic agents, including NSAIDs, ↑ risk of nephrotoxicity; avoid concurrent use.
Medications that compete for active tubular secretion, including acyclovir, cidofovir, ganciclovir, valacyclovir, valganciclovir, or aminoglycosides, may ↑ levels and risk of toxicity; avoid concurrent use.
Carbamazepine, oxcarbazepine, phenobarbital, phenytoin, rifabutin, rifampin, or rifapentine may ↓ levels and effectiveness; concurrent use with oxcarbazepine, phenobarbital, phenytoin, rifabutin, rifampin, or rifapentine not recommended; ↑ tenofovir alafenamide dose to 50 mg once daily when used with carbamazepine.

Drug-Natural Products:

St. John's wort may ↓ levels and effectiveness; concurrent use not recommended.

Route/Dosage ⬆ ⬇

PO (Adults and Children ≥6 yr and ≥25 kg): 25 mg once daily.

Renal Impairment

PO (Adults and Children ≥6 yr and ≥25 kg): Hemodialysis: Administer dose after dialysis session.

Availability ⬆ ⬇

(Generic available)

Tablets: 25 mg
In combination with: bictegravir and emtricitabine (Biktarvy); darunavir, cobicistat, and emtricitabine (Symtuza); elvitegravir, cobicistat, and emtricitabine (Genvoya); emtricitabine (Descovy); emtricitabine and rilpivirine (Odefsey). See Appendix [not included in this PDA edition].

Assessment ⬆ ⬇

Monitor for signs of hepatitis (jaundice, fatigue, anorexia, pruritus) during therapy. On discontinuation of therapy, monitor for clinical and laboratory signs of HBV exacerbation for at least several months after stopping therapy.

Lab Test Considerations:

Test patient for HIV-1 infection before starting therapy; tenofovir alafenamide should not be used alone in patient with HIV-1 infection.
- Monitor liver function tests and HBV levels during and following therapy. If therapy is discontinued, may cause severe exacerbation of HBV.
- Lactic acidosis may occur with hepatotoxicity causing hepatic steatosis; may be fatal, especially in women.
- May cause renal impairment. Monitor serum creatinine, estimated CCr, urine glucose, and urine protein before starting and periodically during therapy. Also assess serum phosphorous in patients with chronic kidney disease. Discontinue tenofovir alafenamide in patients who develop clinically significant ↓ in renal function or evidence of Fanconi syndrome.
- May ↑ ALT, AST, CK, amylase, and LDL cholesterol. May cause glycosuria.

Implementation ⬆ ⬇

PO: Administer once daily with food.

Patient/Family Teaching ⬆ ⬇

Instruct patient to take medication as directed. Avoid missing doses. Advise patient to read Patient Information before starting and with each Rx refill in case of changes.
Advise patient to notify health care provider immediately if symptoms of lactic acidosis (weakness, fatigue, dizziness, muscle pain, trouble breathing, stomach pain with nausea or vomiting, cold extremities, fast or irregular heartbeat) or severe liver problems (yellow skin or whites of eyes, dark tea-colored urine, light-colored stool, loss of appetite, nausea, pain in right side of abdomen) occur.
Instruct patient to notify health care provider of all Rx or OTC medications, vitamins, or herbal products being taken and consult health care provider before taking any new medications.
Rep: Advise women of reproductive potential to notify health care provider if pregnancy is planned or suspected or if breastfeeding. Advise patient taking oral contraceptives to use a nonhormonal method of birth control during therapy. Inform patient of pregnancy exposure registry that monitors outcomes in women exposed to tenofovir alafenamide during pregnancy. Register patient in the Antiretroviral Pregnancy Registry by calling 1-800-258-4263.

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇

Action ⬆ ⬇