When should tenofovir (antiretroviral medication) be initiated?

When to Start Tenofovir

Tenofovir should be initiated immediately upon diagnosis of chronic hepatitis B in patients with detectable HBV DNA (>2000 IU/mL) and evidence of active liver disease, or before starting immunosuppressive therapy/chemotherapy in all HBsAg-positive patients regardless of HBV DNA levels. 1

For Chronic Hepatitis B Treatment

HBeAg-Positive Patients

• Start tenofovir (or entecavir) when HBV DNA >2000 IU/mL with elevated ALT or evidence of significant fibrosis 1
• In patients with compensated cirrhosis, initiate long-term treatment regardless of HBV DNA level 1
• For decompensated cirrhosis, life-long treatment is mandatory 1

HBeAg-Negative Patients

• Initiate therapy with the same criteria: HBV DNA >2000 IU/mL plus elevated ALT or significant fibrosis 1
• Treatment should continue until HBsAg clearance is achieved 1

Before Immunosuppression or Chemotherapy

• All HBsAg-positive patients should start tenofovir (or entecavir) ideally 2 weeks before beginning immunosuppressive therapy or chemotherapy, regardless of HBV DNA level 1
• This applies to high-risk treatments (>10% reactivation risk) including rituximab, high-dose corticosteroids (≥20 mg/day prednisone for ≥4 weeks), anthracyclines, and TNF-alpha inhibitors 1
• Continue treatment during and for at least 12 months after cessation of immunosuppressive therapy (6 months for non-rituximab regimens) 1

For HIV/HBV Coinfection

• Initiate tenofovir-containing antiretroviral therapy immediately upon HIV diagnosis in all HBsAg-positive patients 1
• Tenofovir should be combined with emtricitabine or lamivudine as part of a complete antiretroviral regimen 1
• Do not use tenofovir as monotherapy in HIV/HBV coinfected patients—always use as part of appropriate combination antiretroviral therapy 1
• For patients already on HAART with confirmed lamivudine resistance, add tenofovir immediately 1

For Pregnancy

• Start tenofovir at 24-32 weeks of gestation in HBsAg-positive pregnant women with HBV DNA >200,000 IU/mL (or >10^6-7 IU/mL) to prevent perinatal transmission 1
• Tenofovir is preferred over other nucleos(t)ide analogues due to its FDA pregnancy category B classification, high potency, and extensive safety data 1
• For women with advanced fibrosis or cirrhosis who become pregnant, continue or switch to tenofovir immediately 1
• If used solely for prevention of perinatal transmission, tenofovir may be discontinued within 3 months after delivery 1

For HIV Pre-Exposure Prophylaxis (PrEP)

• Initiate tenofovir disoproxil fumarate/emtricitabine once daily in HIV-seronegative individuals at substantial risk of HIV acquisition 2
• This includes HIV-seronegative partners of HIV-infected persons not consistently virally suppressed 2
• Daily dosing is critical for females, as tenofovir concentrates at 10-fold lower levels in vaginal tissue compared to rectal tissue 2

For HIV Post-Exposure Prophylaxis (PEP)

• Start tenofovir-containing regimen within 72 hours of HIV exposure 3
• Preferred regimens include bictegravir/emtricitabine/tenofovir alafenamide or dolutegravir plus tenofovir with emtricitabine 3
• Continue for 28 days 3

Critical Timing Considerations

Immediate Initiation Required:

• Decompensated cirrhosis 1
• Before starting high-risk immunosuppression (ideally 2 weeks prior) 1
• HIV diagnosis in HBsAg-positive patients 1
• Recurrent hepatitis B post-liver transplantation 1

Delayed Initiation Acceptable:

• Women of childbearing age without advanced fibrosis planning pregnancy in near future may delay until after delivery 1
• However, if advanced fibrosis or cirrhosis is present, treatment must not be delayed 1

Important Caveats

Never discontinue tenofovir abruptly in HBV-infected patients, as severe hepatitis flares can occur, particularly without HBeAg seroconversion 1

When using tenofovir with lopinavir-ritonavir for COVID-19 treatment, consider temporarily switching to entecavir due to drug-drug interactions that increase tenofovir concentrations 1

Assess renal function (creatinine clearance) before initiating tenofovir and monitor periodically, especially in patients at risk for renal dysfunction 4

For healthcare workers performing exposure-prone procedures, start tenofovir if HBV DNA >2000 IU/mL to reduce viral load before resuming such procedures 1