Tenofovir Alafenamide

Indications

Tenofovir Alafenamide is a hepatitis B virus (HBV) nucleoside analog reverse transcriptase inhibitor and is indicated for the treatment of chronic hepatitis B virus infection in adults with compensated liver disease.

Pharmacology

Tenofovir alafenamide is a phosphonamidate prodrug of tenofovir (2'-deoxyadenosine monophosphate analog). Tenofovir alafenamide as a lipophilic cell-permeant compound enters primary hepatocytes by passive diffusion and by the hepatic uptake transporters OATP1B1 and OATP1B3. Tenofovir alafenamide is then converted to tenofovir through hydrolysis primarily by carboxylesterase 1 (CES1) in primary hepatocytes. Intracellular tenofovir is subsequently phosphorylated by cellular kinases to the pharmacologically active metabolite tenofovir diphosphate. Tenofovir diphosphate inhibits HBV replication through incorporation into viral DNA by the HBV reverse transcriptase, which results in DNA chain-termination.

Tenofovir diphosphate is a weak inhibitor of mammalian DNA polymerases that include mitochondrial DNA polymerase γ and there is no evidence of toxicity to mitochondria in cell culture.

Dosage & Administration

Testing Prior To Initiation Of Tenofovir Alafenamide: Prior to initiation of Tenofovir Alafenamide, patients should be tested for HIV-1 infection. Tenofovir Alafenamide alone should not be used in patients with HIV infection

It is recommended that serum creatinine, serum phosphorous, estimated creatinine clearance, urine glucose, and urine protein be assessed before initiating Tenofovir Alafenamide and during therapy in all patients as clinically appropriate

Recommended Dosage In Adults: The recommended dosage of Tenofovir Alafenamide is 25 mg (one tablet) taken orally once daily with food

Interaction

Tenofovir is a substrate of P-glycoprotein (P-gp) and BCRP. Drugs that strongly affect P-gp and BCRP activity may lead to changes in Tenofovir absorption. Consult the full prescribing information prior to and during treatment for potential drug drug interactions.

Contraindications

None

Side Effects

The following adverse reactions are discussed in other sections of the labeling:
  • Lactic Acidosis/Severe Hepatomegaly with Steatosis 
  • Severe Acute Exacerbation of Hepatitis B
  • New Onset or Worsening of Renal Impairment
The most common side effects are headache, stomach pain, tiredness, cough, nausea, back pain

Pregnancy & Lactation

Before you take Tenofovir Alafenamide, tell your healthcare provider about all of your medical conditions, including if you are pregnant or plan to become pregnant. It is not known if Tenofovir Alafenamide will harm your unborn baby. Tell your healthcare provider if you become pregnant during treatment with Tenofovir Alafenamide. 

Pregnancy Registry: There is a pregnancy registry for women who take antiviral medicines during pregnancy. The purpose of this registry is to collect information about the health of you and your baby. Talk with your healthcare provider about how you can take part in this registry.

Use in Special Populations

Pediatric Use: Safety and effectiveness of Tenofovir Alafenamide in pediatric patients less than 18 years of age have not been established.

Geriatric Use: Clinical trials of Tenofovir Alafenamide did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects.

Renal Impairment: No dosage adjustment of Tenofovir Alafenamide is required in patients with mild, moderate, or severe renal impairment. Tenofovir Alafenamide is not recommended in patients with end stage renal disease (estimated creatinine clearance below 15 mL per minute) 

Hepatic Impairment: No dosage adjustment of Tenofovir Alafenamide is required in patients with mild hepatic impairment (Child-Pugh A). The safety and efficacy of Tenofovir Alafenamide in patients with decompensated cirrhosis (Child-Pugh B or C) have not been established; therefore Tenofovir Alafenamide is not recommended in patients with decompensated (Child-Pugh B or C) hepatic impairment

Overdose Effects

If overdose occurs, monitor patient for evidence of toxicity. Treatment of overdosage with Tenofovir Alafenamide consists of general supportive measures including monitoring of vital signs as well as observation of the clinical status of the patient. Tenofovir is efficiently removed by hemodialysiswith an extraction coefficient of approximately 54%

Therapeutic Class

Hepatic viral infections (Hepatitis B)

Storage Conditions

Store below 86°F (30°C). Keep in its original container. Keep the container tightly closed.